question of velocity

[chache]

i was thoroughly suprised by some results that i obtained today while testing a load.

i have been working up a load for my 16" barrel ar-15 using a barnes 50gn varmint grenade and reloader 10. the barnes book calls for max load of 22.2 grains with a velocity of 3202 f/s.

my load development has lead me to the most accurate load being 21.1 grains resulting in a 1/2in. group at 100yds. i anticipated this load would be somewhere in the 3000f/s neighborhood.

i was shocked to see my average velocity was only 2575 f/s with a ES of 44 and an SD of 17. at first glance these all seemed like good stats combined with a great group for an AR. i just didn't think the velocity would be that slow.

i know that shorter barrels results in lesser velocities, but this seems like alot. the barrel length in the book is 24".

what would be the best/smartest move to try and achieve more velocity from this round/gun? with a speed that slow, it seems unlikely that i will be able to reach out to longer distances with acceptable killing effect.

 

[ArchAngelCD]

IMO you got better velocity from a 16" barrel compared to the velocities stated in the book using a 24" barrel than I would expect. If you are shooting 1/2" groups with a semi-auto rifle at 100 yards I would change NOTHING!! You can easily lose 50 fps/per inch of barrel so you're ahead of the game IMO.

Welcome to the forum...

 

[Randy1911]

What was the temp when you where shooting? Cold weather can reduce velocities.

 

[steve4102]

According to Quickload, 3200fps out a 24 inch barrel 223 gets about 2900fps in a 16 inch.
Here is a real test of 223 with shorter barrels. It starts out at 22 inch and goes down to 10 inch. An 8 inch reduction reduces velocity by about 330fps. That still puts you somewhere around 2850-2900fps.
http://www.accuratereloading.com/223sb.html

 

[NCsmitty]

I have a 14" 223 TC barrel on my Contender with a Burris 4x scope and this pistol is very accurate with many combination's of powder and bullet.
I do not have Rel-10 and have never used that powder.
Last summer, I tested and chronographed some loads using 26.5gr of H4895 under 50-52gr bullets. The H4895 load is a middle of the span in charge weight that Hodgdon lists, and I was getting an average of 2820fps from this powder using the 14" barrel.
It's strange that the OP is getting those low numbers across his chronograph with a mid-range powder charge and a 16" barrel.
Rel-10 has a good reputation as a rule.



NCsmitty

 

[chache]

the tempature at the time of shooting was 55 degrees F. light breeze. shooting prone with a bipod and bag.

 

[rcmodel]

Check your crono screen spacing.

If they are even a little too far apart you will loose a lot of the velocity reading.

rc

 

[JimKirk]

I know that the Barnes 50 gr. VG is a totally different bullet.

Alliant web site list 24.2 grs.RL 10X Max under a 50 gr. Nosler BT. If you reduced that by one grain to 23.4 grs. Max for the different bullet, you would still be 2.3 grs. low or 10% lower than the reduced loaded(23.4-21.1=2.3 or .099%)

I think your load is a little light. I have no problem getting 2875 FPS out of a 16" DPMS with 55 gr SBT with Reloder 10X. You should be able to get that 50 gr. VG at least to that or faster.

I would work on up until I started to see some pressure sign or I reached the 23.4 gr. Max.

Jimmy K

Reloder 10X is safe in my gun, It may not be in yours!

 

[lwknight]

Check your crono screen spacing.

If they are even a little too far apart you will loose a lot of the velocity reading.

Those screens are just light difusers. If you have even light they can be removed and the chrono will still work just fine.

 

[Steve C]

i was thoroughly suprised by some results that i obtained today while testing a load.

You get all kinds of surprises in reloading though a drop of 4-500 fps or more from a 8" barrel reduction and shooting from a semi that bleeds of gas to operate the action vrs a sealed chamber bolt action wouldn't be that surprising. Velocity is what it is but accuracy is more important. Any varmint your shoot won't be able to tell the velocity difference and paper doesn't care at all.

 

[chache]

thanks jimkirk, my gun is also a 16" dpms "sweet sixteen" with a bull barrel. i will try the workup that you described. if my gun doesn't like the pressure or i can't seem to make it shoot as accurate, i know i have a moderately fast and very good grouping load already.

 

[JimKirk]

Chache
Same gun!

Here are some loads I am using:

55 gr. Sierra SBT, 23.4 grs. Reloder 10X for a velocity of 2860 fps

60 gr Nosler Partion, 25.0 grs. Reloder 15, 2654 FPS (lower than I would like)Deer load?

Federal bulk pak 55 gr FMJ velocity 2893 FPS

Warning these loads may not be safe in your gun!

Jimmy K