# Firearms and Shooting > Shooting >  What's the Deal?

## Normie

I did some shooting the other weekend with my .260 Rem and 140gr A-Max combo. From 9 measured shots through the chrony I got an average of 2644fps. Using Litz measured G7 BC of .299 for the A-Max Leathel entered all the necessary digits in to his Shooter app for 500m and I think it said 3.2 mils up. I shot it at that and I saw I was about a mil low. I adjusted up .8 mil to 4 mil, shot it again and it was bang on. We had a play with the input speed and to get that calculation it had to be set at 2500fps. WTF? We moved back to 650m and input everything the same as before but adjusted the speed for 2500fps, it said 6.2 mil up. Adjusted and shot it, and it was bang on. I have since entered this into JBM as well and got the same results with the muzzle velocity set at 2500fps. Any ideas what might be going on?

Thanks

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## Wirehunt

Was atmospheric conditions included?

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## StrikerNZ

> Was atmospheric conditions included?


That would be my guess too. Either incorrect atmospherics in the calculator, or your chrony is out. Can't think of anything else that would have a repeatable effect like that.

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## Kiwi Greg

> That would be my guess too. Either incorrect atmospherics in the calculator, or your chrony is out. Can't think of anything else that would have a repeatable effect like that.


+1 

Were there angles involved ?

Did you input the baro pressure or altitude ?

How "good" is your crony ?

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## Normie

I'm not sure what baro was I think we just guessed? Leathel might remember. Angle was corrected for also at 5 degrees. Chrony used was a master chrony. We were getting pretty repeatable results with it but not 100% sure on it's accuracy.

Could Baro cause me to be a whole mil out at 500m? Speed should be close. If anything I'd expect it to be faster than what the chrony was reading but I seem to have a slowish barrel (tight bore).

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## CreepingDeath

Ive got a master chrony and its ok. But you need to verify your drop regardless. It could be alttitude atmospheric settings also. Not being a wise guy here but you didnt mix n match with yards and meters did you? Ive seen that before too.

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## Normie

Nope. Was definitely meters and I got the same result from home on JBM.

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## sneeze

Unless the worlds about to end I don't think atmo will make .8 mill difference at 500. Scope height- accurate zero off the same platform that's being shot etc will all make a diffference . but its far more likely an error from a chrono that relys on ambient light.

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## R93

> Unless the worlds about to end I don't think atmo will make .8 mill difference at 500. Scope height- accurate zero off the same platform that's being shot etc will all make a diffference . but its far more likely an error from a chrono that relys on ambient light.


+1 Chrono, zero or your surface your shooting off has changed if using a pod.

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## Normie

I re-zeroed minutes before the long shots.

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## R93

> I re-zeroed minutes before the long shots.


That leaves 2 other things to eliminate, or a data imput that is causing the difference. What is the book speed for your load? Light for the chrony could be a factor as well.

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## CreepingDeath

Do you have a load zero for powder temp. 20degrees can fuck your shit all up.

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## Normie

Not sure what the book speed is but I'd imagine I'm slower than it should be. The day was perfect for the chrony too. Nice clear day 24 degrees or so in the middle of a paddock.

The powder used is ADI 2209 so fairly temp stable.

 If it helps my load is
Lapua .260 Brass
140gr A-Max
42gr AR2209
CCI BR primer

22" MAB 1:8 barrel

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## R93

> Not sure what the book speed is but I'd imagine I'm slower than it should be. The day was perfect for the chrony too. Nice clear day 24 degrees or so in the middle of a paddock.
> 
> The powder used is ADI 2209 so fairly temp stable.
> 
>  If it helps my load is
> Lapua .260 Brass
> 140gr A-Max
> 42gr AR2209
> CCI BR primer
> ...


There are many variables I know but I used 46grs 2209 in my .260AI and only got 2820fps thru a 24" barrel with the A max. For the same charge in RL-17 I get 2920ish with the same projectile.

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## Normie

Wow. That's a lot slower than I would have thought. I did a ladder for Hodgdon Hybrid 100V and got much better results. At 44gr with no pressure signs at all I got high 2700s fps. 150fps faster for 2 grains more. So I will get some more and do a full work up.

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## Wirehunt

What weight bullet R93?

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## R93

> What weight bullet R93?


140 Amax



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## sneeze

> Not sure what the book speed is but I'd imagine I'm slower than it should be. The day was perfect for the chrony too. Nice clear day 24 degrees or so in the middle of a paddock.
> 
> The powder used is ADI 2209 so fairly temp stable.
> 
>  If it helps my load is
> Lapua .260 Brass
> 140gr A-Max
> 42gr AR2209
> CCI BR primer
> ...


Bullets on target don't lie chroro's do. Some of the worst readings Iv had from a shooting chrony have been in full sun. I have a hunch that pointy high bc bullets are harder for the sensors to read  accurately as well.

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## R93

> Bullets on target don't lie chroro's do. Some of the worst readings Iv had from a shooting chrony have been in full sun. I have a hunch that pointy high bc bullets are harder for the sensors to read  accurately as well.


Too much light is as bad as not enough, alright. Had some ridiculous readings as well.
I haven't tried it but know some people use a vivid to blacken their projectiles so they are easier for the chrony to pick up on bright days. May be worth a go.



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## sneeze

> Too much light is as bad as not enough, alright. Had some ridiculous readings as well.
> I haven't tried it but know some people use a vivid to blacken their projectiles so they are easier for the chrony to pick up on bright days. May be worth a go.
> Sent from my iPhone using Tapatalk. So please forgive my sausage fingers!!!


Yes might help but you just cant trust the shooting chronys. The sensors are very close together so any error is significant and speed readings will change with the light .As has been said many times you need to validate at range whatever machine you use. The CED II with IR screens is the most reliable at a reasonable price but even that works better in a box that cuts out the sun.

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## R93

> The CED II with IR screens is the most reliable at a reasonable price but even that works better in a box that cuts out the sun.


What do you mean by that mate? I have tested some of mine in the dark. Some times faster than my daylight readings and sometimes slower but not by much, over different strings (Usually within 50fps), using the same load.
I would have thought with the ir screens you would get a more accurate and consistent reading at night? Temp?

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## sneeze

Yes dark is good with the ir screens but if in the day time the ambient light still seems to have the ability to interfere and bright sun even more so. Worst is when the sun can hit the sensors direct. Could go some way to explaining the variations you are seeing along with powder/barrel temp maybe. We can put it to the test if you make it to the farm for a few days.

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## veitnamcam

I watched my f1 jump 150 fps as a shadow moved over it, low teck i know but i use it comparatively if at all i e shoot a known load first and add or subtract the variation from actual validated speed.

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## R93

> Yes dark is good with the ir screens but if in the day time the ambient light still seems to have the ability to interfere and bright sun even more so. Worst is when the sun can hit the sensors direct. Could go some way to explaining the variations you are seeing along with powder/barrel temp maybe. We can put it to the test if you make it to the farm for a few days.



Yep, sounds good. I will bring mine up and see if there is any major difference in readings between the 2.

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## sneeze

> I watched my f1 jump 150 fps as a shadow moved over it, low teck i know but i use it comparatively if at all i e shoot a known load first and add or subtract the variation from actual validated speed.
> 
> Sent from my GT-S5360T using Tapatalk 2


Thats it, they serve a purpose but I think to many people put far to much faith in the little numbers that appear on the screen, it seems to have a sort of hypnotic property :Grin:

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## LJP

I always use Brian Litz Bc's. I'd key in what he said for the projectile, key in the atmosphere, use your chrony reading, shoot at range, adjust accordingly then massage the speed till it matches the actual drop....like you have. Even with an Oehler chrony, keying in all the atmospheric conditions etc I can still be out in the drop department.
Chronograph's are at best to give you something to measure ES spread....don't take the actual speed as gospel.

P.S - on a side note the Oehler will almost never give a reading for a Nosler ballistic tip.....Weird! No issue with any other bullet  :Wtfsmilie:

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## gimp

I believe that bullets CAN lie, in the sense that they often lead to wrong assumptions.

Checklist if elevation to hit centre consistently doesn't match chart:
-shooter error
-poor zero
-incorrect range
-mixed unit for range/chart
-shooter error 
-incorrect data entered in calculator to generate chart (BC, speed, height above bore, atmospherics, zero range)
-chronograph incorrect
-scope adjustment not accurate
-angle not accounted for
-incorrect BC
-inconsistent ammunition
-compounding effects of several of the above

A log is important.

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## Norway

> From 9 measured shots through the chrony


My guess. Can't argue with physics, the math is well known, bullet is well documented, the weather isn't a big enough factor so that leaves the measurement?

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## gimp

What zero range for the rifle? And what zero range entered in the app? Because I'm waiting for a plane in Singapore and have had 3 very large black coffees I have had a play with JBM.

With 2644fps and 100m actual rifle zero/100m zero entered in program the 500m elevation is 3.8mil, 650m is 5.9mil (ie the ~corrections that you required to hit)

With 2644fps and 100m actual rifle zero/200m zero entered in program the 500m elevation is 3.1mil, 650m is 5.2mil (ie the 500m ~correction that did not hit, we had no information supplied about misses at 650m)

2500fps is super slow for that powder/charge/bullet/case.

A theory: your rifle is zeroed at 100 meters but the program was set for a 200 meter zero. I can believe an easily overlooked data input error, they happen regularly.


Edit: I think I accidentally did all that with JBM set to G6 not G7 but that just kinda proves my point of how easy it is to miss one little input in a program, doubly so outdoors on a phone etc

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## mucko

> Not sure what the book speed is but I'd imagine I'm slower than it should be. The day was perfect for the chrony too. Nice clear day 24 degrees or so in the middle of a paddock.
> 
> The powder used is ADI 2209 so fairly temp stable.
> 
>  If it helps my load is
> Lapua .260 Brass
> 140gr A-Max
> 42gr AR2209
> CCI BR primer
> ...


ADI book speed is 2675 in a 24" the slight lose in speed would be equal to your 22" so your chrony speed is pretty spot on.

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## L.R

At 2644fps I doubt if the G7 bc will be working out at .299.  Also whats your scope?

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## Normie

Is the G7 BC velocity dependant? My scope is a Sightron SIII 3.5-10 Mil/Mil

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## gimp

> At 2644fps I doubt if the G7 bc will be working out at .299.  Also whats your scope?


You have to drop it to below .200G7 (no way it's that low, considering that they're averaged over velocity range to account for change and  G7 drag model changes very little over a large range of velocities ie, the whole point of using G7 instead of G1) to get the .8mil difference

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## gimp

> Is the G7 BC velocity dependant? My scope is a Sightron SIII 3.5-10 Mil/Mil


Much much less so than G1, hence why it is better

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## Normie

> What zero range for the rifle? And what zero range entered in the app? Because I'm waiting for a plane in Singapore and have had 3 very large black coffees I have had a play with JBM.
> 
> With 2644fps and 100m actual rifle zero/100m zero entered in program the 500m elevation is 3.8mil, 650m is 5.9mil (ie the ~corrections that you required to hit)
> 
> With 2644fps and 100m actual rifle zero/200m zero entered in program the 500m elevation is 3.1mil, 650m is 5.2mil (ie the 500m ~correction that did not hit, we had no information supplied about misses at 650m)
> 
> 2500fps is super slow for that powder/charge/bullet/case.
> 
> A theory: your rifle is zeroed at 100 meters but the program was set for a 200 meter zero. I can believe an easily overlooked data input error, they happen regularly.
> ...


Thanks for the help. Seems like some kind of input error then. Might ask Leathel what the zero range he entered was. Or maybe it is set for POI 1.5" at 100 for one of his rifles?

Zero is definitely 100m, angle of the shot was 5 degrees uphill for both shots. Correction was needed at 500m but not at 650m data was on. Shot was at a clay bank and splash was visible for corrections/misses. Final shot at 650m was a rock about .2 mil wide and 1 high. POI was at the left of the rock but elevation was spot on, wind would have pushed it I guess (light breeze from 5 o'clock).

I know Chronys can be off but I wouldn't have thought by that much.

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## gimp

Data at 650m was only on after you had fudged the velocity though, right?

It is hard to draw exact conclusions from data when the impact points are not well measurable, ie on not steel or paper, it can lead to wrong assumptions hence my comment that bullets can lie. Keeping a log is key as you can refer back to it.

Points:

I have a 22" barrelled .260 belonging to forum superstar "The Kid", previously known as Gordy, sitting in my safe, along with a box of Lapua brass, a 4kg tub of 2209 and a whole shitload of 6.5mm 140gr Amax bullets and I have done a fair bit of research on exactly how to put all these things together. None of it leads me to believe that 42gr of 2209 would push a 140gr at 2500fps in a .260 unless you actually have a 7mm08 and no one bothered to tell you. That to me likely rules out chronograph error.

The potential variation in BC simply will not have that much effect - I don't have Litz' book in front of me here at this Changi airport coffee shop (I do have an extra-large Americano) but the 139gr Scenar G7 varies only .016 from 3,000 to 1,500 fps, the Amax is a very similar form factor and the variation from Litz' average with a 2644fps mv will be much smaller than even that, it will not cause any noticeable change in elevation.

Scope calibration error seems unlikely to me due to two factors: One, the magnitude of the error - it's 20% of your adjustment at 500m. That would mean the scope is incredibly badly calibrated. Two, it's a constant error - .7mil ish at 500m and 650m. If the scope adjustments are incorrectly calibrated, the error would increase with increasing amount of adjustment.

It can't be angle: if the angle was actually steeper than 5° you'd need less adjustment, not more.

If the rifle is zeroed correctly (and ~.7mil is quite off-zero, so you would probably notice) that leaves as far as I can see: 
-shooter error (including possible different POI due to different rest surface or similar)
-input error to ballistic program
-compounding effects of minor errors
-incorrectly reset turrets after zeroing
-mechanical error with rifle such as action screws or suppressor loosening, but that usually results in a random pattern

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## Normie

Yes, muzzle vo was fudged (2500fps) at 650m to get the correction I used. I was shooting prone off bipod and rear bean bag. Pressure on bipod might not have been consistent,1st Variable. I know baro was fudged/guessed that day, 2nd variable (probably not out enough to make such a big error though?). Turrets were not reset after zero so adjustments were added on to this (.5 mil up from previous zero) pretty sure I counted correctly though.

I think i need to shoot it again and do some more logging.

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## L.R

> You have to drop it to below .200G7 (no way it's that low, considering that they're averaged over velocity range to account for change and  G7 drag model changes very little over a large range of velocities ie, the whole point of using G7 instead of G1) to get the .8mil difference


I agree that the G7 wont be that low, however it is something to look out for if you are running bullets slower or faster than their "usual" speeds.  G7 is velocity dependent although not as bad as G1.

Looking back across your data Normie it most likely is a velocity error like others have said.  Your load is what i use in a 6.5x47 so will be rather slow out of the much bigger 260 case.
You are welcome to borrow my Oehler if you like to check you velocity again.

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## Normie

Thanks LR. I might take you up on that. I started getting pressure above 42gr for some reason? Only slight ejector marks and a little cratering though. I might have to do a bit more work with the 2209 but is fine for a hunting load for now. I've looked over my measured shots again and of 42gr and one is way higher than the others at 2694fps so removing that I get an average of 2634fps with an ES of 20fps.

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## L.R

If that load is doing 2500fps as the numbers would suggest its a bit of a lost cause really.  Id try another power I think.  If you'd like to grab the crony just let me know.

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## gimp

I was shooting 42gr of 2209 with 140Amax out of a 20" 6.5x47 too. I found pressure too high and have backed off to 40.9gr (for better accuracy as well, bonus). Previous velocity was 2810fps average via my Shooting Chrony f1 (oh no!) and that velocity was accurate for centre hits to 910meters (As far as I ever bothered to shoot it) so my crappy chrony can't be too far off. I haven't had a chance to chrony the new load but I'm making an educated guess of between 2740-2760fps.

My .260 research for whenever I get around to loading it has indicated that a max load can be anywhere from 41-44gr of 2209 (H4350, it's the same thing) and a 139/140gr will get anywhere from 2700-2850fps in a 22-24 inch barrel, depending on the brass and the chamber and the barrel so 2644fps for 42gr of 2209 sounds reasonable to me. Loads seem to be quite inconsistent but H4350/2209 seems to be universally 'the powder' for a 140 in .260.


Similar to 65x47 actually - some people can't get over 40gr of 2209 with a 140gr without hitting pressure, I was at 42gr and only getting real pressure on 30°+ days when I left my ammo lying in the sun - sticky bolt, ejector mark and 1-2% pierced primers. Normal weather, no signs at all.

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## R93

> Thanks LR. I might take you up on that. I started getting pressure above 42gr for some reason? Only slight ejector marks and a little cratering though. I might have to do a bit more work with the 2209 but is fine for a hunting load for now. I've looked over my measured shots again and of 42gr and one is way higher than the others at 2694fps so removing that I get an average of 2634fps with an ES of 20fps.


Is it a custom or factory setup Normie?
Is there much diff in length between a new case and a once fired one?



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## Normie

My scales are shit really and walk a little but I do re-zero them before each drop of powder. They are always between .2gr out which should be normal for digi scales?? They are Smart Reloader's basic digital model so maybe my weights are out. Would explain the SD being 20fps.

Hey Pete I did a ladder with Hybrid 100V too. Got good results of 150fps more with no pressure signs. Results in Reloading area if you're interested.

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## L.R

Yes Gimp all of that sounds reasonable.  Looks like Normies 42gr load may be a bit slower than 2644 tho unless something else is drastically wrong.  
The load I use now in my 6.5x47 is only 41gr of H4350 and 130 VLDs, its slow at 2777fps but you can't argue with the accuracy even at 1k.

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## Normie

R93 it's a customish rifle. Howa action trued with MAB 1:8 22" PTG reamer for SAAMI chamber spec .298NK .088 FB I think Abe set headspace at 1 thou or 2. Will measure fired case length and get back to you.

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## Normie

When Abe built my barreled action he said my MAB barrel was very tight. He even had to make a new pilot for the reamer, so that might be why I'm slow also?

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## gimp

> Yes Gimp all of that sounds reasonable.  Looks like Normies 42gr load may be a bit slower than 2644 tho unless something else is drastically wrong.  
> The load I use now in my 6.5x47 is only 41gr of H4350 and 130 VLDs, its slow at 2777fps but you can't argue with the accuracy even at 1k.


If he's getting pressure at 42gr 2209 with 140 he should be getting the speed too. It'd be very very unusual to get 200 fps less than everyone else with the same cartridge/powder/bullet combo. Pressure and speed come with each other.

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## R93

> When Abe built my barreled action he said my MAB barrel was very tight. He even had to make a new pilot for the reamer, so that might be why I'm slow also?


No not really. Should be faster if anything with less powder.
Hence my question of measuring length of the 2 cases.

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## Normie

Just done in JBM. ANything not right with my inputs? Corrections are still out.

Trajectory
Input Data
Manufacturer:	Hornady	Description:	Amax (Litz)
Caliber:	0.264 in	Weight:	140.0 gr
Ballistic Coefficient:	0.299 G7 (ICAO)		
Muzzle Velocity:	 2634.0 ft/s	 Distance to Chronograph:	 4.0 m
Sight Height:	 5.28 cm	 Sight Offset:	 0.00 in
Zero Height:	 0.00 in	 Zero Offset:	 0.00 in
Windage:	 0.000 mil	 Elevation:	 0.000 mil
Line Of Sight Angle:	 0.0 deg	 Cant Angle:	 0.0 deg
Wind Speed:	 1.0 m/sec	 Wind Angle:	 90.0 deg
Target Speed:	 0.0 mph	 Target Angle:	 90.0 deg
Target Height:	 30.0 cm		
Temperature:	 25.0 °C	 Pressure:	 29.92 in Hg
Humidity:	 60 %	 Altitude:	 100.0 m
Vital Zone Radius:	 5.0 in		
Std. Atmosphere at Altitude:	 No	 Pressure is Corrected:	 Yes
Zero at Max. Point Blank Range:	 No	 Target Relative Drops:	 Yes
Mark Sound Barrier Crossing:	 No	 Include Extra Rows:	 No
Column 1 Units:	 1.00 cm	 Column 2 Units:	 1.00 mil
Round Output to Whole Numbers:	 No		
Output Data
Elevation:	 1.316 mil	 Windage:	 -0.039 mil
Atmospheric Density:	 0.07251 lb/ft³	 Speed of Sound:	 1135.7 ft/s
Maximum PBR:	 306 m	 Maximum PBR Zero:	 260 m
Range of Maximum Height:	 145 m	 Energy at Maximum PBR:	 1471.9 ft•lbs
Sectional Density:	 0.287 lb/in²		
Calculated Table
Range	Drop	Drop	Windage	Windage	Velocity	Mach	Energy	Time	Lead	Lead
(m)	(cm)	(mil)	(cm)	(mil)	(ft/s)	(none)	(ft•lbs)	(s)	(cm)	(mil)
100	-0.0	-0.0	0.0	0.0	2483.0	2.186	1916.3	0.128	0.0	0.0
125	-1.3	-0.1	0.1	0.0	2444.5	2.152	1857.3	0.161	0.0	0.0
150	-3.7	-0.2	0.3	0.0	2406.4	2.119	1799.8	0.195	0.0	0.0
175	-7.2	-0.4	0.5	0.0	2368.5	2.086	1743.6	0.230	0.0	0.0
200	-11.9	-0.6	0.8	0.0	2331.1	2.053	1688.9	0.265	0.0	0.0
225	-17.8	-0.8	1.2	0.1	2293.9	2.020	1635.5	0.300	0.0	0.0
250	-24.9	-1.0	1.6	0.1	2257.2	1.988	1583.6	0.336	0.0	0.0
275	-33.4	-1.2	2.0	0.1	2220.8	1.955	1532.9	0.373	0.0	0.0
300	-43.2	-1.4	2.5	0.1	2184.8	1.924	1483.5	0.410	0.0	0.0
325	-54.4	-1.7	3.1	0.1	2149.1	1.892	1435.5	0.448	0.0	0.0
350	-67.0	-1.9	3.8	0.1	2113.7	1.861	1388.6	0.486	0.0	0.0
375	-81.1	-2.2	4.5	0.1	2078.7	1.830	1343.0	0.525	0.0	0.0
400	-96.7	-2.4	5.3	0.1	2044.0	1.800	1298.5	0.565	0.0	0.0
425	-113.9	-2.7	6.1	0.1	2009.6	1.769	1255.2	0.606	0.0	0.0
450	-132.7	-2.9	7.0	0.2	1975.5	1.739	1212.9	0.647	0.0	0.0
475	-153.2	-3.2	8.0	0.2	1941.6	1.710	1171.7	0.689	0.0	0.0
500	-175.5	-3.5	9.1	0.2	1908.1	1.680	1131.6	0.731	0.0	0.0
525	-199.6	-3.8	10.2	0.2	1874.8	1.651	1092.5	0.775	0.0	0.0
550	-225.5	-4.1	11.4	0.2	1841.8	1.622	1054.3	0.819	0.0	0.0
575	-253.4	-4.4	12.7	0.2	1809.1	1.593	1017.2	0.864	0.0	0.0
600	-283.3	-4.7	14.1	0.2	1776.6	1.564	981.0	0.909	0.0	0.0
625	-315.4	-5.0	15.5	0.2	1744.4	1.536	945.8	0.956	0.0	0.0
650	-349.5	-5.4	17.1	0.3	1712.4	1.508	911.4	1.004	0.0	0.0
675	-386.0	-5.7	18.7	0.3	1680.7	1.480	878.0	1.052	0.0	0.0
700	-424.7	-6.1	20.4	0.3	1649.2	1.452	845.4	1.101	0.0	0.0
725	-465.9	-6.4	22.2	0.3	1618.0	1.425	813.7	1.151	0.0	0.0
750	-509.6	-6.8	24.2	0.3	1587.0	1.397	782.8	1.203	0.0	0.0
775	-556.0	-7.2	26.2	0.3	1556.3	1.370	752.8	1.255	0.0	0.0
800	-605.0	-7.6	28.3	0.4	1525.9	1.344	723.7	1.308	0.0	0.0
825	-656.9	-8.0	30.5	0.4	1495.7	1.317	695.3	1.362	0.0	0.0
850	-711.8	-8.4	32.9	0.4	1465.8	1.291	667.8	1.418	0.0	0.0
875	-769.7	-8.8	35.3	0.4	1436.2	1.265	641.1	1.474	0.0	0.0
900	-830.8	-9.2	37.9	0.4	1406.9	1.239	615.2	1.532	0.0	0.0
925	-895.3	-9.7	40.6	0.4	1377.9	1.213	590.1	1.591	0.0	0.0
950	-963.2	-10.1	43.4	0.5	1349.2	1.188	565.8	1.651	0.0	0.0
975	-1034.7	-10.6	46.3	0.5	1320.9	1.163	542.3	1.713	0.0	0.0
1000	-1110.1	-11.1	49.4	0.5	1292.9	1.138	519.5	1.775	0.0	0.0
28/03/13 18:51, JBM/jbmtraj-5.1.cgi

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## gimp

> My scales are shit really and walk a little but I do re-zero them before each drop of powder. They are always between .2gr out which should be normal for digi scales?? They are Smart Reloader's basic digital model so maybe my weights are out. Would explain the SD being 20fps.
> 
> Hey Pete I did a ladder with Hybrid 100V too. Got good results of 150fps more with no pressure signs. Results in Reloading area if you're interested.


Yeah, I saw that, looked like good speeds, might be best to just go with it, as long as it's temperature stable and actually available...

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## L.R

Id say Normies barrel is getting on the short side to get those speeds from a 260, and as you know a longer barrel will get more velocity for the same pressure, so pressure and velocity are not exclusive to each other.

If his loads are doing the 2644 the crony says they are then it only really leaves a scope adjustment issue dosent it?

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## gimp

> Just done in JBM. ANything not right with my inputs? Corrections are still out.


Missing line of sight angle... But it doesn't make much difference at 5°

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## gimp

> Id say Normies barrel is getting on the short side to get those speeds from a 260, and as you know a longer barrel will get more velocity for the same pressure, so pressure and velocity are not exclusive to each other.
> 
> If his loads are doing the 2644 the crony says they are then it only really leaves a scope adjustment issue dosent it?


It could be an issue of the scope being near the edge of adjustment and the adjustment fucking up because of that - how much travel have you got from zero? Up, and sideways. I had a VX3 that would go sideways when you got near the top. 

Barrel length doesn't make that much difference.

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## L.R

> No not really. Should be faster if anything with less powder.
> Hence my question of measuring length of the 2 cases.
> 
> Sent from my iPhone using Tapatalk. So please forgive my sausage fingers!!!


May explain early pressure signs tho.

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## L.R

> It could be an issue of the scope being near the edge of adjustment and the adjustment fucking up because of that - how much travel have you got from zero? Up, and sideways. I had a VX3 that would go sideways when you got near the top. 
> 
> Barrel length doesn't make that much difference.


I dont agree with you on barrel length, I find it makes a big difference especially on 6.5's.  Build yourself a short barreled 6.5x284 and see how it goes, they are fucken useless!

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## gimp

It also could be the 'bullets can lie' thing - if you're not shooting something easily measurable it's possible to draw wrong conclusions from your results. Rocks/banks aren't so scientific. 


Basically I think he just needs to go confirm zero, re chrony, check scope travel, make sure everything is tight, and shoot more logging the results.

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## gimp

> I dont agree with you on barrel length, I find it makes a big difference especially on 6.5's.  Build yourself a short barreled 6.5x284 and see how it goes, they are fucken useless!


We're talking a 22" .260 here though, not 12”....

But on the subject, 

Tussock cut his 6.5x47 from 26" to 22" with loss of 10fps. His load of 42gr was exactly the same as mine (my load development initially consisted of pinching ammo from his shed when I was in a hurry) and doing about 2fps different average out of my 20” to his 22”

We got nearly 2900fps from a 20" barrelled BSA 6.5x55 back in 2009 with N560 when we got snowed in and had nothing better to do, without any real pressure signs

Norway has a 18.5" 6.5-284 and enjoys it - although he is very conservative with his loading compared to all of us.

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## Normie

Zero is 10 mil up from bottom (2 turns x 5 mil p/turn) I think I have 30 mil total elevation so should be in the middle of adjustment range. 22" is short but not that short I think tight bore might have more to do with the slow factor.

I don't have direct access to anywhere to shoot really only through Leathel. Next time we go I'll measure 5 shots through chrony check zero and set up the gong this time and get a little more scientific up in this bitch.

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## R93

Nothing to do with the bore unless you are coppering/fouling up.
You can possibly eliminate the concern of what I think it is, buy measuring the brass.



Sent from my iPhone using Tapatalk. So please forgive my sausage fingers!!!

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## tui_man2

> Zero is 10 mil up from bottom (2 turns x 5 mil p/turn) I think I have 30 mil total elevation so should be in the middle of adjustment range. 22" is short but not that short I think tight bore might have more to do with the slow factor.
> 
> I don't have direct access to anywhere to shoot really only through Leathel. Next time we go I'll measure 5 shots through chrony check zero and set up the gong this time and get a little more scientific up in this bitch.


On the tighter bore barrels I have done loads for an with yours and Adams is tight on his wsm. They have all got pressure before others had with same projectile powder combos in most cases can be couple of gr earlier. all still shot well apart from Adams only likes some projectiles.

It don't explain the big adjustment to get right drop tho and the speed was never down as much as yours only 100fps ish. Just go through everything again and double check it all. I'd think you will find little fault in there somewhere. Am check scope as well make sure clicks aren't smaller than what they say. . . . .No one has said that yet?

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## Normie

Case length is about the same. i don't have a a way of accurately measuring the shoulder. The 30 cal hole of my hex comparator doesn't fit over fired case necks. I'll see if I can jammy something up to measure it. It is the shoulder length you're referring to right?

No copper fouling either

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## L.R

> We're talking a 22" .260 here though, not 12....
> 
> But on the subject, 
> 
> Tussock cut his 6.5x47 from 26" to 22" with loss of 10fps. His load of 42gr was exactly the same as mine (my load development initially consisted of pinching ammo from his shed when I was in a hurry) and doing about 2fps different average out of my 20 to his 22
> 
> We got nearly 2900fps from a 20" barrelled BSA 6.5x55 back in 2009 with N560 when we got snowed in and had nothing better to do, without any real pressure signs
> 
> Norway has a 18.5" 6.5-284 and enjoys it - although he is very conservative with his loading compared to all of us.


Ok Gimp, you must have stumbled on a secret that no one else has ever discovered.  I wonder why we all walk around with these long barrels then? We must all be stupid.

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## gimp

> Ok Gimp, you must have stumbled on a secret that no one else has ever discovered.  I wonder why we all walk around with these long barrels then? We must all be stupid.


I don't understand what you think is so shocking about a 20-22 inch barrel? Yes you get more speed from a longer barrel. Yes the returns are diminishing the longer you go. Yes long barrels are a pain and I don't like them and don't give a damn about the theoretical 50fps I'm missing out on. Longest I have on anything is 20" and I definitely haven't noticed any downside at all.

It's not particularly crazy to expect Normie to be able get 2700-2800 fps from a 22" barrel with what is widely considered the optimum powder for the cartridge when a heap of people are reporting doing just that, when I'm doing it with a 2" shorter barrel and a smaller case, and when he is getting that with a different powder?

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## sneeze

Gimp misinterpretation of poi isn't a lie its an error but I sure you know what I was referring to. 

Id check the imputs and shoot some groups on  paper at  range.

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## Wildman

I get an average of 2712fps from a 22" MAB barrel with 43gr AR2209 and the 140gr Hornady SST's. I very much doubt 1gr drop in powder and a slightly different bullet would make 200fps difference. Check your inputs :Have A Nice Day:

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## gimp

> Gimp misinterpretation of poi isn't a lie its an error but I sure you know what I was referring to. 
> 
> Id check the imputs and shoot some groups on  paper at  range.


I was using 'lie' as a figure of speech, as in your results can appear different to what they really are. Not meant to be negative on you or anyone else. Just be careful to log and watch the trends before coming to too much of a conclusion about things

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## Dead is better

> I get an average of 2712fps from a 22" MAB barrel with 43gr AR2209 and the 140gr Hornady SST's. I very much doubt 1gr drop in powder and a slightly different bullet would make 200fps difference. Check your inputs


Thats what i get with my 6.5x55 t3 44gn 2209 140g amax. Its accurate to the click out to 700m but i haven't yet tested further. Good to see this is a typical result then

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## Norway

> Shooting Chrony f1 (oh no!)


Shooting Chrony is not bad, it's just that they are light dependant and reading will vary with the light.

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## Norway

> Build yourself a short barreled 6.5x284 and see how it goes, they are fucken useless!


Short barreled 6,5x284 out to 1150 meters, 20" and not 18,5" as Gimp said.



You'll get:
A compact rifle that let's you react fast enough to make use of the shooting opportunities.
Reduced velocity and reduced supersonic reach.
For all practical purposes, no change in wind drift.

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## L.R

May as well have a 260. Same velocity for less powder burnt. Short barrel rifles are great, I have several, however there is no denying you lose velocity with them, I don't buy this shit about only loosing 10 fps by cutting 6" off a barrel.

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## Norway

No you lose 30 msec doing that.

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## Norway

No you lose approximately 30 msec doing that.
To stay within sane pressures, I think it would be difficult to bring a 260 up to 830 msec in a 20".

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## jakewire

> Thats what i get with my 6.5x55 t3 44gn 2209 140g amax. Its accurate to the click out to 700m but i haven't yet tested further. Good to see this is a typical result then


That's interesting as I get average of 2709 with my sako  x55 with the same bullet using 46grn of the same powder.
Perhaps I'd better chrony it again.

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## gimp

> May as well have a 260. Same velocity for less powder burnt. Short barrel rifles are great, I have several, however there is no denying you lose velocity with them, I don't buy this shit about only loosing 10 fps by cutting 6" off a barrel.


1: it was 4"

2: a single 6.5x47 specifically,  check with Tussock if you like but that's what he got, it is unusual but there it is. I'm not saying that you can go cut a 7mm Rem mag down and it'll get faster or something stupid. Just that a lot of the time the benefits of a short barrel outweigh the downsides for an actual practical rifle

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## gimp

> That's interesting as I get average of 2709 with my sako  x55 with the same bullet using 46grn of the same powder.
> Perhaps I'd better chrony it again.


Different rifles, brass, primers, can do that

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## gimp

> Shooting Chrony is not bad, it's just that they are light dependant and reading will vary with the light.


I know  :Have A Nice Day:  no problems with mine when used in clear direct sunlight, readings appear 'accurate' and have done so for the 5 years I've had it. Even put it next to jake wires (he didn't trust his) and they read the same.

The super chrono looks nice for more portability though.

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## tui_man2

> No you lose approximately 30 msec doing that.
> To stay within sane pressures, I think it would be difficult to bring a 260 up to 830 msec in a 20".


Sorry *normie* for the steel an cut an paste of your info..........
As the title suggests I did a ladder test recently with my 22" .260 and below are the results.

Load details:
 OAL 2.865" (mag length)
 140gr A-Max
 .260 Lapua Brass
 CCI BR Primer
 Hodgdon Hybrid 100V Powder

41gr - 2556
 41.5gr - 2583
 42gr - 2632
 42.5gr - 2704
 43gr - 2693 (1st shot after letting barrel cool for a little while)
 43.5gr - 2744
 44gr - 2797
 44.5 - 2879 (Definitely load too hot. Major extractor mark and tight bolt lift)

Going by the little loss is speed you are saying *norway* that shows me the smaller case of the 260 beating an lasting longer than your 6.5-284 witch i think personally is a pig or a cal apart from in a longer target barrel shorter barrel may as well go smaller better counterpart

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## Normie

What about parallax? Could it cause a .8 mil shift in POI? I might not have adjusted the parallax before shooting. Can't remember.

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## gimp

maybe.

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## L.R

Fuck Tussock, I didn't realise what a genius you were.  

I didn't understand anything you said in that post, went right over my head with that one.

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## Toby

Does that make fluting a heavy barrel a waste of time as it would be letting the heat escape in certain places making those waves of heat not equal?

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## gimp

Lighter weight without compromising stiffness is the other reason.

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## Toby

Would having barrels that are tapered have an effect on accuracy? the heat taking longer to escape on the fatter end and so on?

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## tui_man2

> No, the waves of heat was a figure of speech really. More surface area to dissipate heat is probably the only practical reason for fluting.


And weight

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## gimp

Yeah I'm not really into fluting

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## Kiwi Greg

Thanks *Tussock* I have been thinking about trying to express sensibly the thick/heavy/hot internally barrel theory for a while.

Some of the Target guys fire a heap of rounds in fairly short time.

I have often wondered how the Carbon wrapped barrels get on with thier very thin metal barrels surrounded by resin etc.

The heat has to get out & away from the throat as fast as possible to avoid excessive erosion.

I noticed a while ago now that you could fire 10 shot mag or two out of my 338 Norma 98B Barrett & it would stay reasonably cool.

The alloy chassis would heat up taking the heat quickly out of the barrel, it has a big shank/shoulder area around & in front of the chamber which has plenty of contact with the chassis.

Fluting is mainly cosmetic I believe, with a small decrease in weight & increase in surface area.

A fluted barrel will be stiffer than a barrel of the same length & weight.

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## Gillie

I am not sure I am following your reasoning Tussuck.
A thinner / lighter barrel will erode slower because although it heats up faster it also cools down faster… therefore the bore surface temperature would be lower when firing the next shot... I think this would only be the case after a certain amount of shots and a certain time frame. 

I absolutely agree with you that both a heavy and a light barrel will see the same heat input. But I would have thought that heat transfers much faster through steel than it does from steel to air. My line of thinking is that the heat would average over the mass of the barrel faster than it would be dissipated from the outside surface to the air. This would mean that the heavier barrel will absorb that heat and remain cooler after a short time when compared to a lighter barrel. 

This is how I interpret Greg’s observation above as well. His rifle chassis is sucking the heat out of the barrel faster than the heat would normally dissipate from the barrel outside surface.

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## Nibblet

I would agree with you Gillie. My understanding is that a thicker heavy barrel is essentially a giant heat sink. And as such requires more energy to heat in its entirety.

Think of trying to use a gas torch to weld together thick steel, requires a lot more time to heat than a thinner piece as the heat is conducted and diffused throughout the entire piece.

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## Nibblet

Just some light thermal dynamics reading taken from wiki

Heat conduction, also called diffusion, is the direct microscopic exchange of kinetic energy of particles through the boundary between two systems. When an object is at a different temperature from another body or its surroundings, heat flows so that the body and the surroundings reach the same temperature, at which point they are in thermal equilibrium. Such spontaneous heat transfer always occurs from a region of high temperature to another region of lower temperature, as described by the second law of thermodynamics.

Conduction
Main article: Thermal conduction
On a microscopic scale, heat conduction occurs as hot, rapidly moving or vibrating atoms and molecules interact with neighboring atoms and molecules, transferring some of their energy (heat) to these neighboring particles. In other words, heat is transferred by conduction when adjacent atoms vibrate against one another, or as electrons move from one atom to another. Conduction is the most significant means of heat transfer within a solid or between solid objects in thermal contact. Fluids—especially gases—are less conductive. Thermal contact conductance is the study of heat conduction between solid bodies in contact.[6]
Steady state conduction (see Fourier's law) is a form of conduction that happens when the temperature difference driving the conduction is constant, so that after an equilibration time, the spatial distribution of temperatures in the conducting object does not change any further.[7] In steady state conduction, the amount of heat entering a section is equal to amount of heat coming out.[6]
Transient conduction (see Heat equation) occurs when the temperature within an object changes as a function of time. Analysis of transient systems is more complex and often calls for the application of approximation theories or numerical analysis by computer.

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## Savage1

A heavier barrel also offers a larger surface are, probably around 2x, with which it can dissipate the heat. So a heavy barrel should dissipate a certain amount of energy quicker than a standard profile.

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## veitnamcam

Yes and no, a light and heavy barrel subjected to the same heat input.
lets say light gets to 300dc and heavy gets to 100dc. The light will lose more heat to atmosphere even allowing for less surface area simply due to temperature differential to atmospheric temp.

Heat will conduct far quicker threw steel than air, touch a red hot bit of steel 820dc or wave your hand threw a lpg oxy flame 1200dc.

A heaver barrel will take longer to heat and cool down than a light, as a barrel heats the temperature differential between the flame front in your precious throat and barrel temp gets less and so does the rate of cooling of the throat.

If what you are worried about is the temp and subsequent erosion of the throat, then a heavy barrel will keep that throat cooler for longer of your first string of rapid fire. then it will take forever to cool.

Simple physics  :Have A Nice Day:

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## veitnamcam

If you take the same quantity of coffee,sugar,boiling water and cold milk and make one cup of coffee milk in cup first and another the same but milk last which will be hotter?

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## veitnamcam

The coffee analogy 

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## sneeze

> If you take the same quantity of coffee,sugar,boiling water and cold milk and make one cup of coffee milk in cup first and another the same but milk last which will be hotter?


So after seven pages we can conclude that Normie was .8 mill out because of the milk in his coffee :Thumbsup:

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## veitnamcam

> So after seven pages we can conclude that Normie was .8 mill out because of the milk in his coffee


Finally someone who understands me  :Grin: 

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## Nibblet

Or was it too much coffee giving him the shakes?

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## Normie

I don't have milk in my coffee. Sorry fellas. Back to the drawing board.

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## veitnamcam

My attempt at laymans terms for 3rd form physics was a fail then.
Basicly Tussoks rebuttal said exactly what i had just said  :Grin: 

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## veitnamcam

And its hard to make a cup of coffee with no coffee :what: :Grin: 

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## veitnamcam

Yes and no, a light and heavy barrel subjected to the same heat input.
lets say light gets to 300dc and heavy gets to 100dc. The light will lose more heat to atmosphere even allowing for less surface area simply due to temperature differential to atmospheric temp.

Heat will conduct far quicker threw steel than air, touch a red hot bit of steel 820dc or wave your hand threw a lpg oxy flame 1200dc.

A heaver barrel will take longer to heat and cool down than a light, as a barrel heats the temperature differential between the flame front in your precious throat and barrel temp gets less and so does the rate of cooling of the throat.

If what you are worried about is the temp and subsequent erosion of the throat, then a heavy barrel will keep that throat cooler for longer of your first string of rapid fire. then it will take forever to cool.

Simple physics  :Have A Nice Day:

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## veitnamcam

If you take the same quantity of coffee,sugar,boiling water and cold milk and make one cup of coffee milk in cup first and another the same but milk last which will be hotter?

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## veitnamcam

The coffee analogy 

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## sneeze

> If you take the same quantity of coffee,sugar,boiling water and cold milk and make one cup of coffee milk in cup first and another the same but milk last which will be hotter?


So after seven pages we can conclude that Normie was .8 mill out because of the milk in his coffee :Thumbsup:

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## veitnamcam

> So after seven pages we can conclude that Normie was .8 mill out because of the milk in his coffee


Finally someone who understands me  :Grin: 

Sent from my GT-S5360T using Tapatalk 2

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## Nibblet

Or was it too much coffee giving him the shakes?

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## Normie

I don't have milk in my coffee. Sorry fellas. Back to the drawing board.

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## veitnamcam

My attempt at laymans terms for 3rd form physics was a fail then.
Basicly Tussoks rebuttal said exactly what i had just said  :Grin: 

Sent from my GT-S5360T using Tapatalk 2

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## veitnamcam

And its hard to make a cup of coffee with no coffee :what: :Grin: 

Sent from my GT-S5360T using Tapatalk 2

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