Thread: Lower than expected velocities

I don't think increasing neck tension increases velocity/pressure much.
Consistent neck tension affects ES of load.
The load in question has a ES of 30 which is not too bad.

I suspect the load is slightly down on pressure despite the data and I'll be doing a ladder test while looking for pressure signs and velocity/pressure spikes.

Greetings,
Over the years I have noticed significant differences in load data for 6.5mm cartridges in particular the 6.5-06. This has become worse since Americans "discovered" the 6.5mm bore. The Continentals had been working with 6.5mm cartridges since the 1890's and had worked out how to deal with the long projectiles and fast powders. Most of these rifles had slightly or sometimes more loose groove dia. When A2 introduced the 6.5-06 as a factory cartridge they seem to have used much tighter groove barrel specs which push up both pressure and velocity. The data put out by Hodgdon for the 6.5x55 agrees pretty well with my results but the 6.5-06 I have been working with (put together in the 1990's) produces significantly less velocity than the data would suggest, much closer to vintage chronographed data from the 1980's. To me this seems likely to be the barrels.
Regards Grandpamac.

2506 is a great cal - got my first stag with an early a-bolt (straight fluted bolt) and 100gn Hornadys. From memory 50gn 2209 around 3100.


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Greetings,
A check through my records yielded the following data. Both rifles are Remington 700 .308W.
Rifle 1 is my 45 plus year old .308W with the barrel cut to 20". Velocity with the 150 grain Hornady soft point is 2,675 fps with 44 grains of AR2206H. The rifle has been used for a little hunting and rather more target shooting and has had a little over 1,000 rounds through it.
Rifle 2 is a a much newer rifle with 100 or so rounds down the 24" tube. 45 grains of AR2206H with the 150 grain Hornady produced 2,865 fps and factory 150 grain Corelokt 2,850 fps.
Adjustments for the extra grain of powder 50 fps and 4 inches of barrel 100 fps give us a corrected velocity of 2,825 fps for my old rifle. Powder is the same lot and the Hornady and Win cases used are near identical in weight and likely capacity.
So we should expect a velocity loss of around 100 fps for a 20" barrel, not 300 fps. Some factory ammo produces significantly less velocity than claimed even in a standard 24" barrel and there is only one fix for that.
Regards Grandpamac.

Originally Posted by grandpamac

Greetings,
A check through my records yielded the following data. Both rifles are Remington 700 .308W.
Rifle 1 is my 45 plus year old .308W with the barrel cut to 20". Velocity with the 150 grain Hornady soft point is 2,675 fps with 44 grains of AR2206H. The rifle has been used for a little hunting and rather more target shooting and has had a little over 1,000 rounds through it.
Rifle 2 is a a much newer rifle with 100 or so rounds down the 24" tube. 45 grains of AR2206H with the 150 grain Hornady produced 2,865 fps and factory 150 grain Corelokt 2,850 fps.
Adjustments for the extra grain of powder 50 fps and 4 inches of barrel 100 fps give us a corrected velocity of 2,825 fps for my old rifle. Powder is the same lot and the Hornady and Win cases used are near identical in weight and likely capacity.
So we should expect a velocity loss of around 100 fps for a 20" barrel, not 300 fps. Some factory ammo produces significantly less velocity than claimed even in a standard 24" barrel and there is only one fix for that.
Regards Grandpamac.

I know - that speed figure of about 300fps is working backwards off the range drops for the trajectory to get to a muzzle velocity that makes the pill (with it's BC) match the rainbow. There's a lot of doubt and I need to get back to the range to confirm a few things up - although I very much suspect that the issue here is the ammo is not even close to the claimed velocity figure that Winchester has slapped onto their box. I am halfway wondering if they've used a 26" test barrel, which could be good for a bit more than 150fps over the 20" and then allowing for difference factor between barrels which could be 100fps - that may explain what's going on for me.

Originally Posted by No.3

I know - that speed figure of about 300fps is working backwards off the range drops for the trajectory to get to a muzzle velocity that makes the pill (with it's BC) match the rainbow. There's a lot of doubt and I need to get back to the range to confirm a few things up - although I very much suspect that the issue here is the ammo is not even close to the claimed velocity figure that Winchester has slapped onto their box. I am halfway wondering if they've used a 26" test barrel, which could be good for a bit more than 150fps over the 20" and then allowing for difference factor between barrels which could be 100fps - that may explain what's going on for me.

Greetings No 3.
Trying to guess velocity based on range drops is a pretty rough method. Just chronograph the load and you will know the velocity assuming a half decent chronograph. The BC for a projectile is not carved in stone and varies with conditions and even from shot to shot. Most data these days is for 24 inch barrels and I think that your actual velocity is higher than you think.
Regards Grandpaneil.

Originally Posted by grandpamac

Greetings No 3.
Trying to guess velocity based on range drops is a pretty rough method. Just chronograph the load and you will know the velocity assuming a half decent chronograph. The BC for a projectile is not carved in stone and varies with conditions and even from shot to shot. Most data these days is for 24 inch barrels and I think that your actual velocity is higher than you think.
Regards Grandpaneil.

I have a Magnetospeed V3, but problem was I had it set up with the can on the rifle and subsequent testing with the subs confirmed that the chrony does not like the extra clearance between the bullet flight path and the sensor bayonet when the can is fitted. I have seen people get a spare sensor bayo and trim the attachment belt area right down to fix this, or the other option is a Xero chrony I guess. The trajectory vs pill weight is coming out with a velocity figure within 25fps for everything I've run the numbers through - about 5 apps now.

It's indicating that the velocity is WAY below factory box figures (2880 muzzle vs calculated less than 2600) regardless of any other factors, and the impact point at 300m was stupid low. It's not confirmed for velocity but it's near enough that the other variables are only going to make a minor difference to the calculated fps - I need to find several hundred fps to get the impact point at 300m close to box trajectory. As is with a point blank hold the pill will drop right under a large bodied animal if aiming for the centre of organs/hilar area. Really need more than a 225m point blank range out of a .308 to be honest!

I agree it's not the most accurate but it's enough to know that the ammo is not useable as is, so the answer is more testing firstly and secondly abandon the Winchester ammo (not in stock now so can't be replaced anyway) and find a load that will perform. The Win ammo was a holdover from another .308 and I was just using it expecting similar performance out of the newer firearm but ended up with a WTF? moment.

If I could find three rounds of the Sako I'd bung that through and see what it does as a couple of 50-round boxes of that would see me sorted for the next few years of hunting out of this rifle.

Originally Posted by No.3

I have a Magnetospeed V3, but problem was I had it set up with the can on the rifle and subsequent testing with the subs confirmed that the chrony does not like the extra clearance between the bullet flight path and the sensor bayonet when the can is fitted. I have seen people get a spare sensor bayo and trim the attachment belt area right down to fix this, or the other option is a Xero chrony I guess. The trajectory vs pill weight is coming out with a velocity figure within 25fps for everything I've run the numbers through - about 5 apps now.

It's indicating that the velocity is WAY below factory box figures (2880 muzzle vs calculated less than 2600) regardless of any other factors, and the impact point at 300m was stupid low. It's not confirmed for velocity but it's near enough that the other variables are only going to make a minor difference to the calculated fps - I need to find several hundred fps to get the impact point at 300m close to box trajectory. As is with a point blank hold the pill will drop right under a large bodied animal if aiming for the centre of organs/hilar area. Really need more than a 225m point blank range out of a .308 to be honest!

I agree it's not the most accurate but it's enough to know that the ammo is not useable as is, so the answer is more testing firstly and secondly abandon the Winchester ammo (not in stock now so can't be replaced anyway) and find a load that will perform. The Win ammo was a holdover from another .308 and I was just using it expecting similar performance out of the newer firearm but ended up with a WTF? moment.

If I could find three rounds of the Sako I'd bung that through and see what it does as a couple of 50-round boxes of that would see me sorted for the next few years of hunting out of this rifle.

Greetings @No.3,
I would suggest chronographing the ammo without the can as this will give you an accurate velocity to start with. As you speak of a point blank range I assume that you have the rifle zeroed at 200 metres or there about and not just a little high at 100. Unlike Hawkes Bay you are blessed with many rifle ranges in your area. PM me with your actual results if you wish.
Regards Grandpamac.

Book max for w780 is 55.5gr @deerhunta

Originally Posted by Longrun

Book max for w780 is 55.5gr @deerhunta

Greetings,
I note that W780 is at least the fourth failed attempt by Winchester to come up with a rifle powder in the slow category. The Staball trio is the latest attempt by Hodgdon which may be more successful. Time will tell. W780 was produced for less than a decade being discontinued around 10 years ago. Not a powder I would be tempted to hot rod with.
GPM.

Make that fifth failed attempt. Just found another from the early 1970"s

Originally Posted by Longrun

Hi,
First time with garmin chrony.

25-06 near top of load data.
100gr hot cor instead of 100gr partition in load data.
Bullet seated about diameter of bullet into case.

Recorded velocity 3013fps Data velocity 3300fps

I appreciate that it's a different bullet that I have seated quite far out. 22inch barrel.

Questions. Would seating the bullet in further generate much more pressure/velocity?

Should I increase the charge beyond data to achieve something like 3300fps?

I have the same story going on with a 6.5 x 55.20inch barrel.
Also a 250savage that is recording velocities as expected.

Check what barrel length the load data you are using is for. Typically it is for a 24 Inch barrel.

Is it a new barrel? Some need a couple of hundred rounds through them and then get a velocity increase. And some manufacturers have slow barrels for some reason (looking at you Tikka)

ballistic charts never killed a deer

I had a Sako Finnlight in 2506, it worked very well, but i also, found it slower than book speeds by 200 fps, I feel the 2506 really needs, a bit longer barrel than 22" to get full performance, I hove a couple friends with them with 25" barrels, they seam to get much better speeds with same loads,
Never the less, even with a bit slower speed, than book, a 120gr soft point at 2900 or 110gr at 3050 or so if a very fine killer of cloven hoofed game.
I found all Factory non premium 2506, slower than expected, I ended up handloading, settling on 110 AB, and 120 gr Hornady. Now days i would have up the charge a bit to get more speed, as long as accuracy didn't worsen, back in my 2506 days, I was pretty green to hand loading.
The only other rifle caliber's, I have owned, that had so many straight down, on the spot, kills in a row, is a 270 win with 110gr and a .264 win with 130gr, the 270 is long gone, and the 264 hasn't been out for ages.
Like many, I've swing back to more moderate calibers, and loads, no longer need the fastest and flattest, A change bought about by better optics and distance measures,