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Posted: 6/13/2010 4:59:39 PM EDT
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IMI M855 2009: Range Report
Lot #00219/K 
This M855 load has a heavy collet crimp at the case mouth. 
The bullet has a cannelure and the case mouth is sealed with asphalt sealant. 
The bullets loaded in this new lot lack the green painted tip of the older lots. 
The primer pockets are sealed and crimped. 
The cartridge is charged with ball powder. 
An accuracy evaluation of this lot of ammunition was performed following my usual protocol. Shooting was conducted from a concrete bench from a distance of 100 yards (confirmed with a laser range finder.) The test vehicle was a 16” Colt HBAR with chrome-lining, a NATO chamber and a 1:9” twist. This is the barrel found on the Colt 6721 Tactical Carbine. The barrel was free-floated with a LaRue Tactical handguard. 
The fore-end of the carbine rested in a Sinclair Windage Benchrest and the butt-stock rode in a Protektor rear-bag. Sighting was accomplished via a Leupold VARI-X III set at 25X magnification and adjusted to be parallax-free at 100 yards. A mirage shade was attached to the objective-bell of the scope. Naturally, the wind conditions were monitored using a Wind Probe. The set-up was very similar to that pictured below. 
The Wind Probe. 
No animals were harmed during the testing of this ammunition! A 10-shot control group was fired using match-grade hand-loads topped with Sierra 55 grain BlitzKings. The extreme spread of that group measured 0.89”. 
Three 10-shot groups of the IMI M855 were obtained for analysis. The extreme spreads of those groups measured: 2.72” 2.19” 2.24” for a 10-shot group average of 2.38”. The three 10-shot groups were over-layed on each other using RSI Shooting Lab to form a 30-shot composite group. The mean radius for the composite group was 0.76”. 
IMI M855 lot #00256/A (circa early-mid 2000s?) 
For comparison, I’m including the results of an accuracy evaluation of a previous lot of IMI M855 (lot #00256/A). Testing of this lot was carried-out in the same manner as described above. The test vehicle for this evaluation was a free-floated 20” Colt HBAR with chrome-lining, a NATO chamber and a 1:7’ twist. 
The three 10-shot groups obtained using this lot of M855 had extreme spreads that measured: 2.14” 3.01” 1.71” for a 10-shot group average of 2.29”. As before, the three 10-shot groups were over-layed on each other using RSI Shooting Lab to form a 30-shot composite group. The mean radius for this composite group was 0.68”. The 30-shot composite groups from both lots are pictured below for comparison. 
M855 lot #00256/A was chronographed using an Oehler 35-P with “proof-screen” technology. All strings of fire consisted of 10 shots each. All of the velocities posted below are MUZZLE velocities which were calculated from the instrumental velocities using Oehler’s Ballistic Explorer software. Chronograph data for M855 lot #00219/K will be posted in this thread, hopefully, within the next few weeks. 
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THANK YOU SIR!
I'm curious as to the chronograph comparison....I look foward to those results, but the big winner here... if I got this right, the latest IMI M855 is grouping with an ES within .5" of the earlier lot lot of IMI...but these lastest results were shot out of a 4" shorter barrel. Did I get that right? Many thanks Molon. |
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Quoted:
Molon, could you keep an eye out for widely varying OAL. I heard that it could be an issue. Magazine length FMJ rounds like M855 are jumping more than 0.220" to the lands of a NATO chamber. Variations in OAL with this type of ammunition are not a big issue with the accuracy spectrum involved. 
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Quoted:
THANK YOU SIR! I'm curious as to the chronograph comparison....I look foward to those results, but the big winner here... if I got this right, the latest IMI M855 is grouping with an ES within .5" of the earlier lot lot of IMI...but these lastest results were shot out of a 4" shorter barrel. Did I get that right? Many thanks Molon. Well, if you compare the average extreme spread of the three 10-shot groups from each load, the two loads only differ by an ES of 0.09". (2.38" vs 2.29") |
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Quoted:
Has anyone "sectioned" this ammo to see if it has the "penetrator" tip, and has anyone done fragmentation tests on this ammo? I only ask because a friend of mind is in desperate need of money, and has offered me a lot of ammo at a good price. It will frag just like most all M855 IMI has a Mild steel insert around 10.5grs I bet if its M855 it has the insert I use to visit the IMI Forum Back in the day I know IMI makes a few different types of 5.56mm |
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Quoted:
Quoted:
Has anyone "sectioned" this ammo to see if it has the "penetrator" tip, and has anyone done fragmentation tests on this ammo? I only ask because a friend of mind is in desperate need of money, and has offered me a lot of ammo at a good price. It will frag just like most all M855 IMI has a Mild steel insert around 10.5grs I bet if its M855 it has the insert I use to visit the IMI Forum Back in the day I know IMI makes a few different types of 5.56mm I remember reading AO years ago the their were two different types of 855 frag rates. One was inside the test medium, while the other was as the projectile was exiting the test medium. This is why I asked the question. |
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Quoted:
I remember reading AO years ago the their were two different types of 855 frag rates. One was inside the test medium, while the other was as the projectile was exiting the test medium. This is why I asked the question. As far as genuine Lake City M855 and M193 are concerned, there is a wide variation in their depth to fragmentation. 
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Molon, What program do you use to size your groups and calculate mean radius ? Thanks Also, I know 855 has severe yaw issues but was unaware that 193 had that bad of a problem. As far as the 75/77 gr OTMs do they have a certain percentage of Yaw issues? Do you have much data about the 69gr BTHPs aside from the stuff in your reference thread? |
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