I picked up 500 rnd of this UAE-manufactured ammo from AIM this week.

I shot a box  (19 round clocked, one failure to record velocity) of that through a bushmaster 14.5 inch barrel with a phantom brake/FH (the spikey looking one from ADCO).  I followed that up with 20 rounds of Radway green for comparison, because thats what I had on hand.

Date 10/1/05
ADCOM 5.56x45 ball M855, 2004 manufacture
case markings  5.56   AD  04
baro 30.64 start, 30.64 end
temp 50 F start, 54 F end
RH 81% start, 76% end

2943  2958  3002  2956  2985
2954  2889  3002  2030  2937
2922  2961  2871  2916  2898
2875  2930  2923  2950  no-vel

average  2936.9   sdev  37.7
========================

for comparison, the Radway Green:
Date 10/1/06
Radway Green from AIM, 1989 manufacture
case markings  RORG  "circle with cross"  89
baro 30.64 start  30.65 end
temp 54 F start  60 F end
RH  76% start  67% end

2895  2931  2918  2882  2886
2923  2942  2900  2911  2914
2932  2971  2966  2924  2916
2976  2909  2898  2903  2914

average 2920.6  sdev 26.5
========================

I realise there is a difference between M855 and SS109; I don't have any other M855 to compare to the ADCOM.  The accuracy of the ADCOM is comparable to the radway, which has shot well for me.  I don't have groups because I was in a somewhat ungainly position shooting through the chrony.  Range had other shooters, and there was no opportunity to "fiddle" with shooting position relative to the chrony.  Maybe someone else can comment on accuracy.

RMT

Thanks for the info!
bump

from the ammo oracle:

"The ammo is still loaded with SS-109 bullets and labeled as SS-109, but it is nowhere near the M855 velocity specifications."

I guess I was not aware of the nuances of the differences, but it does appear, at least from these two samples, that the ADCOM is equivalent to the RADWAY.  Maybe someone could apply further statistics to verify the means are not different enough to be labled as from seperate populations.  

RMT

Thanks for the info.

SS109 is a bullet designation, M855 is a load designation.
All proper M855 loads have the SS109 bullet.

If you refer to the FRAG CHART, you'll see that the avg velocity for the M855 load from a 14.5" barrel is 2907 fps.

The ADCOM ammo you tested met that velocity, so one would have to assume it's loaded to M855 specs.

Here is a sampling of what we chronographed today.
Further data can be found here

Ammo ADCOM M855 (Lot #AML99010-002 - Headstamp AD 5.56 99)
Bushmaster 14.5"-1/9
2930
2916
3006
2949
3014
2963 Avg.
44.5 Std. deviation

DPMS 14.5"-1/7
2873
2842
2846
2900
2942
2880.6 Avg.
41.5 Std. deviation

Bushmaster 16"-1/9
2960
2972
3019
2982
2992
2985 Avg.
22.4

Colt 16"-1/9
2982
2893
2980
2935
2918
2941.6 Avg.
38.9 Std. deviation

Hoosier, do you assign any significance to the fact that the 1/7 twist had lower avg. velocity for all trials vs. the 14.5" Bushy 1/9?

Quoted: Hoosier, do you assign any significance to the fact that the 1/7 twist had lower avg. velocity for all trials vs. the 14.5" Bushy 1/9?

Nate,

We were quite surprised by that AND the fact that the BM 14.5" average velocities were nearly identical to the BM 16" carbine and actually higher than the Colt 16" carbine.

More detail on the weapons used.
1.) Bushmaster A3 14.5" M4 profile 1/9 barrel w/permanent Phantom YHM-28
2.) RRA lower/CMMG (DPMS) A2 14.5" M4 profile 1/7 barrel w/permanent Phantom YHM-28
3.) Bushmaster A2 16" HBAR 1/9 barrel with plain muzzle
4.) Colt MT6731 A3 16" HBAR 1/9 barrel with plain muzzle

On another unrelated note, the muzzle flash of the plain muzzled carbines in daylight could easily be described as a 'fireball' while those with the Phantom FH had no discernible flash whatsoever.

All barrels perform differently. Some are faster or slower than others.
Example: I have 3 20" stainless Douglas barrels. 2x 1/7" and 1x 1/8".
The 1/8" is 100fps slower than the 2 1/7"s.
They all have the same chamber and were using the same ammo.

Mark

SD is pretty darn good for "surplus" ammo. A bit over 1% SD is not bad at all.

Quoted: All barrels perform differently. Some are faster or slower than others. Example: I have 3 20" stainless Douglas barrels. 2x 1/7" and 1x 1/8". The 1/8" is 100fps slower than the 2 1/7"s. They all have the same chamber and were using the same ammo. Mark

SF, love your "SIG" and combat is well in Michigan. Stop by sometime and I'll throw some toys your way and supply the ammo.

Quoted: Quoted: All barrels perform differently. Some are faster or slower than others. Example: I have 3 20" stainless Douglas barrels. 2x 1/7" and 1x 1/8". The 1/8" is 100fps slower than the 2 1/7"s. They all have the same chamber and were using the same ammo. Mark SF, love your "SIG" and combat is well in Michigan. Stop by sometime and I'll throw some toys your way and supply the ammo.

Yes the Sig line...came from an infamous "chromed barrel" thread
Thanks for the offer....who knows, I might just have to take you up on that one of these days, but the next stop is AZ.
Don't know if they see much combat there though

Mark

Picked up 1000 today myself along with madman_kirk.  Don't have a chrony, but very happy with the results we were getting.  100 yard groups for me were good coming out of my 1/9 HB 24" stainless DPMS upper.  Ammo looks and shoots clean also.  99 headstamp today, but kirk picked some up last week with 04 that was shooting good for him also last Saturday.  I'll definitely be getting more.

Quoted:
All barrels perform differently. Some are faster or slower than others.
Example: I have 3 20" stainless Douglas barrels. 2x 1/7" and 1x 1/8".
The 1/8" is 100fps slower than the 2 1/7"s.
They all have the same chamber and were using the same ammo.

Mark

SF/Mark, this is something I have always wondered about.  Is this just the minute differences in major and minor diameter caused by tool wear during the barrel cutting (or whatever rifleing process is used).  Ie, different net shear on the bullet as it travels the barrel.  I would think the variability in the bullets would completely wash-out any barrel diameter contribution.  Or more a final finish difference on the internal surfaces...?  If it was just energy being tied up in the rotational spin-up, I would expect the slower twist to be faster.

I now have 5 K of this ammo and all of it looks very good. All 99 manf date.

Quoted: Quoted: All barrels perform differently. Some are faster or slower than others. Example: I have 3 20" stainless Douglas barrels. 2x 1/7" and 1x 1/8". The 1/8" is 100fps slower than the 2 1/7"s. They all have the same chamber and were using the same ammo. Mark SF/Mark, this is something I have always wondered about.  Is this just the minute differences in major and minor diameter caused by tool wear during the barrel cutting (or whatever rifleing process is used).  Ie, different net shear on the bullet as it travels the barrel.  I would think the variability in the bullets would completely wash-out any barrel diameter contribution.  Or more a final finish difference on the internal surfaces...?  If it was just energy being tied up in the rotational spin-up, I would expect the slower twist to be faster.

Honestly, I don't know what the answer is.
One guy I know has a .308 (a Parker-Hale M85) and his barrel is 100fps faster than all comparable M85's.
I think it's just a tolerance thing.
I don't think twist rate has any effect on velocity.
But I do know that they lose velocity through wear, so the 1/8" twist barrel might've been a bit more generous in the first place

Mark

yeah, I forgot about the gas seal being the primary driver on velocity.  It just may take an LSDYNA fluid-structure-interaction analysis to fully determine what all the contributors are.  I'll get right on that...heh.