Ballistic truing conundrum

Been playing with loads for 284 & 7SAUM using RL26 with 162 ELDMs and 165 Norma BondStrike. Long story short ended up with some nice tight groups (0.5 - 0.6 moa) and velocities around 3000 fps. Both 284 & SAUM are 22in barrels. The 284 running 3010fps with 162 AMAX & SAUM 2995fps with 162 ELDMs. Interesting and in line with early load dev with different powders, get more speed with the 284, and in this case (RL26) less powder.
Anyhooow, then ran some shots with the SAUM past couple of calm days with 162 ELDMs at 625 yards to validate speeds & drops. Using Hornady bc calculator & Kestrel 5700 both gave me 10moa or there abouts as the come up. But shots were consistently high going over top of 10in gong, and after close inspection of target area & some rough maths estimated that 9 moa should be on the money. So back to shooting position, dialed 9.0 moa come up & confirmed POA and POI were bang on (within 1 inch).
Scope (VX6) is zeroed for 200 yards, 1.3in high at 100.
Never came across a case before where dial up needs to be reduced significantly???
Most times if scopes don’t dial true moa, they dial less - like IPHY or in some cases less. Leupy scopes in my experience tend to dial IPHY or slightly more.
If you follow the truing logic of correcting muzzle velocities to account for drop, then to get 9.0 moa come up you’d expect muzzle velocity of ~3100 fps. No way can I see that out of SAUM & 22in bbl. Similarly can’t imagine BC differences explaining 10% change 10 to 9moa??

Any of you LR experts out there have any thoughts or ideas to explain this mystery?

Have you proved the scopes adjustments on paper at 100m ?

No, have to do that but I’ve never come across a VX6 that dials more than true moa. Let alone 10% more?!
But it’s the only thing that seems to fit the observed facts.

What about air pressure ? Altitude can affect it a lot ( weather, not so much) and it just changes the apparent BC in proportion .

We are about 80m above sea level, pressure according to weather maps past few days is 1015 - 1020 hPa. Can’t see that changing anything much. Also any air pressure factors should be covered with ballistics calc from the Kestrel 5700.

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Originally Posted by chainsaw

We are about 80m above sea level, pressure according to weather maps past few days is 1015 - 1020 hPa. Can’t see that changing anything much. Also any air pressure factors should be covered with ballistics calc from the Kestrel 5700.

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Good chance you zero not perfect at 200.
Best practice is 100m or yard zero as yocan really get it perfect .
If your zero is perfect trust the app doing the validation in the kestrel
Honestly watch Tod hodnet's videos on truing he really knows his shit.
1.3 inches seems quite low for above bore height to.
I do heaps of validation shooting and in your case I'm picking its something simple.


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The “1.3in” above is the height of POI (centre of grp) above POA at 100 yards. I checked this at the range a week ago. I agree it might not be exactly zero at 200, but it’s within a gnats whisker. The scope height is 1.6in and I used that input to Ballistic calcs.

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Originally Posted by chainsaw

The “1.3in” above is the height of POI (centre of grp) above POA at 100 yards. I checked this at the range a week ago. I agree it might not be exactly zero at 200, but it’s within a gnats whisker. The scope height is 1.6in and I used that input to Ballistic calcs.

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OK, as I say I'm doing this all the time.
Make your point of impact smack on at 100 then validate from that.
If you want a 200 zero just leave your scope set on that.
I can guarantee this works otherwise you will out clever yourself!
If you have a kestrel 5700 you have the best ballistic solver on the market.
I'm using mine daily and it's never wrong as long as you put the right info in

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Re zero at 200. The further out you zero the more error you can induce. Make sure it's exactly 200m. Or is it yards? That could cock it up.
Check atmospherics are correct, scope height etc. It all needs to be as close to perfect as you can get it if your going through a trying process.
625 is also on the close side for trying. 800m is usually the standard.
How good is your shooting? We're you shooting in a position or off something that the rifle could jump slightly higher? Carbon bipod on rocks or something? Or jambing the rifle down into the ground to get elevation?
It's not very hard to induce 1moa of shift, I've seen a lot more.

What's the objective in asking?
To me I'd call this "dope" and get on with my day... but i spose if you want to dial in a computer thingy then yeah... you need to work out the whyfor.

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Originally Posted by 11mms

What's the objective in asking?
To me I'd call this "dope" and get on with my day... but i spose if you want to dial in a computer thingy then yeah... you need to work out the whyfor.

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There is nothing worse when taking a shot and doubting you accuracy.
Nothing better than taking a shot when you know you've done every thing perfectly!
Man I have seen some shit zeroed rifles and they wonder why they can't hit any thing.

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Originally Posted by andyanimal31

There is nothing worse when taking a shot and doubting you accuracy.
Nothing better than taking a shot when you know you've done every thing perfectly!

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Yeah but my point was, now he knows... 10 clicks, on his scope, with his load, from his gun, at 625 = whatever.
Regardless of what any app says... I'll always verify POI through all ranges I want to shoot.

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Originally Posted by andyanimal31

OK, as I say I'm doing this all the time.
Make your point of impact smack on at 100 then validate from that.
If you want a 200 zero just leave your scope set on that.
I can guarantee this works otherwise you will out clever yourself!
If you have a kestrel 5700 you have the best ballistic solver on the market.
I'm using mine daily and it's never wrong as long as you put the right info in

Sent from my SM-A226B using Tapatalk

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Yes, the Kestrel 5700 is a wonderful bit of kit. I don’t doubt it for a second, but also use the Hornady BC calculator as cross check when something like this happens.
I do the scope zeroing at 100 yards, just set to get the POI 1.3in high = 200 yd zero.

Had exactly the same issue with my 284 and the LRABs. Never figured it out. Ended up fudging the figures to make it all line up and validated out to 900 and just went with it. Then one day the barrel decided it didn't like the accubonds any more courtesy of fire racking around the throat and some pitting halfway down the tube.

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Originally Posted by Skirch

Re zero at 200. The further out you zero the more error you can induce. Make sure it's exactly 200m. Or is it yards? That could cock it up.
Check atmospherics are correct, scope height etc. It all needs to be as close to perfect as you can get it if your going through a trying process.
625 is also on the close side for trying. 800m is usually the standard.
How good is your shooting? We're you shooting in a position or off something that the rifle could jump slightly higher? Carbon bipod on rocks or something? Or jambing the rifle down into the ground to get elevation?
It's not very hard to induce 1moa of shift, I've seen a lot more.

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Zeroing done at 100 yards, see other post below. I never use metres, all measurements are inches, yards, moa, etc.
The 200 zero might be 205 or 195, but that makes naff all difference - maybe 0.1 or 0.2 moa at 625yrd. Not a cause for 1moa delta.

Atmospherics etc, covered by Kestrel. Again any small change or error is going to be sfa.

Yes ideally I’d do truing at longer range but 625yd is the max I have access to.

How good is the shooter? Good point. Good enough to consistently shoot 1/2 moa grps in light weight (6lb bare rifle) hunting rifles.

Shooting position- a bit average. After this shit wet winter the cattle have munted the paddocks good and proper. So finding a spot with out too many lumps and bumps not easy. Bipod (Spartan) had good lock up and stable forward load plus rear bag allowing a fairly solid platform.
Shots on gong poi was within 1in of POA so despite a less than ideal ground conditions I feel the results validate the accuracy.

My next step is to calibrate the scope dial up on paper at 100 yards.
As mentioned at start of thread have never seen a Leupy dial more than true moa. But maybe this is an exception?

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Originally Posted by 11mms

What's the objective in asking?
To me I'd call this "dope" and get on with my day... but i spose if you want to dial in a computer thingy then yeah... you need to work out the whyfor.

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I want to understand “the why”. That’s the way my brain works & as @andyanimal31 says confidence in data is critical. Last thing you need is the double guessing yourself.

If the dope came in low, ie need to dial up a few clicks I can understand that & have seen it plenty of times before.
But to be 10% out the other way is a massive outlier and something I need to get to bottom of.

I'd be inclinded to try truing it at a few different ranges, say 350y and 500y.
That will tell you if your velcoity is right or not.

Unless the atmposherics are messed up in your ballistic calculator (seems unlikely that both would be out), it's either;
-Bad zero (It'll be easy to see if your zero was off 1 moa, 2"@ 200yards)
-Your scope
-Your chrony (if the 284 was ok then rule that out)
-Funky stuff happening with wind down range (if you didn't notice the same issue with the 284 then rule that out too).

The scope might not be dialing correctly (Gimp had a video a few years back of a Mark 6 that dialed on the piss). You can test this by doing a box test, or just a simple elevation test. I had a VX5 that didn't dial right, the clicks were quite calibrated/manufactured correctly.
If you can easily pull the scope off and put it on a 22 then you can do a full "tall target" tracking test without wasting 30 rounds of 7SAUM ammo.

Have you validated the BC of the bullets is correct to what you are using? Sometimes the advertised figures aren't right and the error you get can be surprising. I didn't see that mentioned anywhere above? It might not explain all of the error you are experiencing but there may be several smaller errors adding up. Have you tried a different chrony as well?

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Originally Posted by No.3

Have you validated the BC of the bullets is correct to what you are using? Sometimes the advertised figures aren't right and the error you get can be surprising. I didn't see that mentioned anywhere above? It might not explain all of the error you are experiencing but there may be several smaller errors adding up. Have you tried a different chrony as well?

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I thought this too, just forgot to added it to my post...
That would also show up by validating at more distances.

Hornady list the BC for the bullet in velocity bands, if you have a multi BC function on your calculator then use that, otherwise using their middle number is generally more accurate.
The G1/G7 BC for the 162 ELD-M is 0.655 / 0.329.

https://www.hornady.com/support/ballistic-coefficient

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Originally Posted by No.3

Have you validated the BC of the bullets is correct to what you are using? Sometimes the advertised figures aren't right and the error you get can be surprising. I didn't see that mentioned anywhere above? It might not explain all of the error you are experiencing but there may be several smaller errors adding up. Have you tried a different chrony as well?

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It sounds like he is using a kestrel 5700.
If that's the case they have applied ballistics custom drag curves.
They aren't wrong end of story.
To me, the culprit is the 1.3 high at 100 for a 200 yero
Actually zero at 100 and try your data out from that.
I have seen most things in my time.
Just had one the other day with the guy having problems.
Have you zeroed?
Yep, shows me a tiny 3 shot group through the dot.
I went and validated and it was coming up at a lower speed than I though it should be.
Rang me to say way low at 350.
Fucked if I know,recheck the zero.
Guess what, zero out, fixed that and bang on out to a km and back


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Thanks all for the comments and feedback. To pick up on a couple of points above :

BC - i used 0.67 G1 as listed by Hornady. If anything manufacturers stated BCs tend to be “optimistic” and derived under ideal conditions. In my case if a lower BC were correct this would not explain the data I’m getting. Dialing 9.0 moa compared to ballistic program 10.12 moa. A lower BC would require a bigger come up, not smaller. Or conversely the BC would need to be up around 0.7 or something to make the numbers line up.

Chrony error, using a Magneto Speed. Have used on many other rifles previously and not observed it to be inaccurate previously. Every measuring device has a degree of precision or error, so possibly 1-2% out ? But to get the observed come up difference of 9 vs 10 moa requires a muzzle velocity of ~3100 fps compared to my measured 2995. Just can’t see 3100fps being possible with a 22in bbl SAUM. Wouldn’t it be nice though !! :thumbsup:

Scope dial up calibration - did that today with tall target at 100.0 yards measured at the erector. Surprisingly the VX6 is dialing better than moa !!
First time I’ve seen this in a Leupy or any scope for that matter. This one is dialing 1.083in per moa, instead of 1.05in/moa. That translates to a 3% error. So dialing 9.0 moa is actually giving a come up around 9.2 moa.
So this still leaves 0.75 - 0.8 moa “unexplained”.
Or my muzzle velocity is something like 3075fps ?

At this point my guess is I’m dealing with several compounding errors.
1. Scope dial up
2. Zero maybe slightly out, should be able to verify this next weekend at NZDA range if weather plays ball.
3. Chrony might be reading slightly low

I agree @Beetroot, running checks at 300 &/or 500 yards would be wise and helpful.

When I replaced my mark 4 with a vx 6 I had the same issue as you but using 162 amaxs in a rem mag. Thought it was the scope adjustment as has been mentioned above (around 1.08in/moa) so just fudged the speed (increase of about 75fps) to match. A while later when I tried a different load in the rifle using 180eldms I just assumed it would be the same with the scope over adjusting, but was surprised when it came to checking at distance is was actually back to around 1.05in/moa. Still have no idea why but it's consistent so havnt worried.

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Originally Posted by chainsaw

Thanks all for the comments and feedback. To pick up on a couple of points above :

BC - i used 0.67 G1 as listed by Hornady. If anything manufacturers stated BCs tend to be “optimistic” and derived under ideal conditions. In my case if a lower BC were correct this would not explain the data I’m getting. Dialing 9.0 moa compared to ballistic program 10.12 moa. A lower BC would require a bigger come up, not smaller. Or conversely the BC would need to be up around 0.7 or something to make the numbers line up.

Chrony error, using a Magneto Speed. Have used on many other rifles previously and not observed it to be inaccurate previously. Every measuring device has a degree of precision or error, so possibly 1-2% out ? But to get the observed come up difference of 9 vs 10 moa requires a muzzle velocity of ~3100 fps compared to my measured 2995. Just can’t see 3100fps being possible with a 22in bbl SAUM. Wouldn’t it be nice though !! [emoji106]

Scope dial up calibration - did that today with tall target at 100.0 yards measured at the erector. Surprisingly the VX6 is dialing better than moa !!
First time I’ve seen this in a Leupy or any scope for that matter. This one is dialing 1.083in per moa, instead of 1.05in/moa. That translates to a 3% error. So dialing 9.0 moa is actually giving a come up around 9.2 moa.
So this still leaves 0.75 - 0.8 moa “unexplained”.
Or my muzzle velocity is something like 3075fps ?

At this point my guess is I’m dealing with several compounding errors.
1. Scope dial up
2. Zero maybe slightly out, should be able to verify this next weekend at NZDA range if weather plays ball.
3. Chrony might be reading slightly low

I agree @Beetroot, running checks at 300 &/or 500 yards would be wise and helpful.

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If you are using the kestrel use the bc data on the kestrel phone app.
A g1 bc for the saum will not be correct.
Either use the kestrel g7 or custom drag curves it comes with.

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Pretty sure the Hornady guys recommend adjusting velocity, not BC, for 'truing'.

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Originally Posted by caberslash

Pretty sure the Hornady guys recommend adjusting velocity, not BC, for 'truing'.

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As a rule it is best practice.
If you have a brian litz bc/applied ballistics/kestrel use their custom drag curves.
It's all sorted with out mucking around with velocity bands.
If you have all the right info your chrony speeds will be very close to real world results.
Don't fuck with the Bc's

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Originally Posted by chainsaw

At this point my guess is I’m dealing with several compounding errors.

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This. Accuracy is minimising all of the errors you can so that the ones you can't have a smaller effect (eg meteorological factors).

https://www.nzhuntingandshooting.co....et-test-35034/
https://www.nzhuntingandshooting.co....34/index3.html Post #40

Range finding error ?
625 is a random number, so I guess the target is at a convenient spot with a rising bank behind the target and perhaps some rounding of the distance to the nearest quarter-hundred ?
Its tricky to get an exact measurement on flat or rolling ground and a laser might not register off a small target frame like a gong. It could be confirmed by parking a vehicle at the firing point and ranging back to it while standing at the target.
For my 7mm08 the difference in drop from 625 yd back to 600yd is almost 1 moa.

It’s an accurate 625yd, measured with 2 different RFs and one i have used multiple times over the years. I range it every time & get the same distance. And never before with various different calibres, rifles, scopes have I encountered the situation where I need LESS dial up by a factor of 10%. In other cases the dial up predicted by ballistic programs is very close to correct or slightly low, ie need to come up 1 or 2 clx.

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Originally Posted by chainsaw

It’s an accurate 625yd, measured with 2 different RFs and one i have used multiple times over the years. I range it every time & get the same distance. And never before with various different calibres, rifles, scopes have I encountered the situation where I need LESS dial up by a factor of 10%. In other cases the dial up predicted by ballistic programs is very close to correct or slightly low, ie need to come up 1 or 2 clx.

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If this is a target you have shot multiple times with no issues, your chrony has proven to be reliable in the past, and on the same day you shot another rifle that performed as expected (so no funny wind conditions) then you can work out what variables you can discount and which ones to focus on.

Yep, checking (again) the zero is next on the list. Should get that next weekend if weather plays ball.

SAUM 162 ELDM RL26 scope DOPE update
An update on previous posts, chasing down a difference of +1moa at 625 yards. Ballistic solvers predicted a 10moa come up, compared to my dialed come up of 9moa which gave a variance of 1-1.5in POI (low) vs POA. This set me re-checking some of the basics
1. Scope (VX6) dial up calibration. Turns out it’s dialing 1.083 in/moa, a 3% error. This equates very closely to 0.25moa at 625 yds
2. POI vs POA, checking measurements again and confirmed 1-1.5 in low at 625yd. This also equates to ~0.25 moa at 625yds. 



Correcting for 1&2 above my dial up should have been 9.25 moa and that equates to 9.5moa once you factor in the scope cal. This leaves an “error” of 0.5 moa to account for.


3. Re-check 200 yd zero, equates to 1.3in high at 100. Went to range this past weekend & put 5 shots down range. Average of 5 gave 1.5in high at 100. This equates to zero of 210 yards.

So correcting for all 3 above I still need to DOPE the muzzle velocity to get 9.5moa answer from solver. Adjusting speed to 3020fps (vs 2995fps measured) with a 210yd zero does the trick.

I also ran calcs using no adjustment for zero, just tweaking velocity (needs 3050 fps) to get 9.5 moa at 625yd. And another set just tweaking zero (needs 220 yd zero) leaving speed at 2995fps. However all 3 versions are less than 0.25 moa difference from 350 yards all the way out to 900, which is further than anything I’d attempt on game.
So I’ll proceed using 3020fps for muzzle velocity, 210 yd zero and adjusting the come up to account for scope dialing more than true moa.
Job done.

does your solver allow for scope correction?
for your 200yard zero why not just shoot at 200m and zero there?

Kestrel 5700 I think does have an option to input scope correction factor. But I’ve not played around with that feature as yet. Actually it’s pretty easy run the math in your head. 500 - 700 yards it’s reduce come up by 0.25 moa. Then 750 - 900 it’s reduce by 0.5 moa. Won’t be shooting any further than that & sub 500 it’s less than 1/4moa so you can’t dial it anyways.
Metres vs yards. Yeah, nah. My brain is wired in yards, feet, inches & moa.

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Originally Posted by chainsaw

Kestrel 5700 I think does have an option to input scope correction factor. But I’ve not played around with that feature as yet. Actually it’s pretty easy run the math in your head. 500 - 700 yards it’s reduce come up by 0.25 moa. Then 750 - 900 it’s reduce by 0.5 moa. Won’t be shooting any further than that & sub 500 it’s less than 1/4moa so you can’t dial it anyways.
Metres vs yards. Yeah, nah. My brain is wired in yards, feet, inches & moa.

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If you have nightforce you don't need that bit!

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not true. kahles had been tested as the most accurate dialing.

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Originally Posted by blair993

not true. kahles had been tested as the most accurate dialing.

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You can't bang six inch spikes in with a kahles.
To be fair nf has been the bench mark for modern optics and accurate dialing for years.
A lot of manufactures are now catching up that is a fact.
I support nf as they are a family owned southern hemisphere business that produces some of the toughest and most accurate optics in the world.

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Or take a 7.62x39 sideways thru the ocular and still keep functioning until the marine returned to base to get it replaced.

Sure they started out as Liteforce and still have an Adelaide address but I see NF as an American company now.
Oh, and I own their scopes as well, only humble NXSs though.

Recall the vid where a I guy shot a very respectable group with a NF scope . Fired a shot, removed scope from QD mounts, threw it as hard as he could down range, retrieved, re-attached, fired next shot, and so on.

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Originally Posted by zimmer

Or take a 7.62x39 sideways thru the ocular and still keep functioning until the marine returned to base to get it replaced.

Sure they started out as Liteforce and still have an Adelaide address but I see NF as an American company now.
Oh, and I own their scopes as well, only humble NXSs though.

Recall the vid where a I guy shot a very respectable group with a NF scope . Fired a shot, removed scope from QD mounts, threw it as hard as he could down range, retrieved, re-attached, fired next shot, and so on.

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Night force Australia has a subsidiary company USA.
The family that own and run it are very much aussie based with a couple of trips a year to Idaho.
They still do quit a bit of product development there in Aussie to as a very shooting oriented family.


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Even if it doesn't solve your problem go and shoot at 200yards! Don't trust the math of 1.3 high at 100.

Theres something about that distance. My DOPE from applied ballistics is always slightly out at 200m even when I've validated much further out.