The muzzle velocities for the Lake City M855A1 are summarized in the table below.
For comparison, the next two tables show the muzzle velocities for legacy military 5.56mm ammunition that also uses 62 grain projectiles: M855 and MK318 Mod 0.
Accuracy
I conducted an accuracy (technically, precision) evaluation of the Lake City M855A1 ammunition following my usual protocol. This accuracy evaluation used statistically significant shot-group sizes and every single shot in a fired group was included in the measurements. There was absolutely no use of any group-reduction techniques (e.g. fliers, target movement, Butterfly Shots).
The shooting set-up will be described in detail below. As many of the significant variables as was practicable were controlled for. Also, a control group was fired from the test-rifle used in the evaluation using match-grade, hand-loaded ammunition; in order to demonstrate the capability of the barrel. Pictures of shot-groups are posted for documentation.
Shooting was conducted from a concrete bench-rest from a distance of 100 yards (confirmed with a laser rangefinder.) The barrel used in the evaluation was free-floated. The free-float handguard of the rifle rested in a Sinclair Windage Benchrest, while the stock of the rifle rested in a Protektor bunny-ear 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 used. Wind conditions on the shooting range were continuously monitored using a Wind Probe. The set-up was very similar to that pictured below.
The Wind Probe.
The test vehicle for this accuracy evaluation was one of my semi-automatic precision AR-15s with a 20” stainless-steel Lothar-Walther barrel. The barrel has a 223 Wylde chamber with a 1:8” twist. Prior to firing the Lake City M855A1, I fired a 10-shot control group using match-grade hand-loads topped with the Sierra 77 grain MatchKing (without a cannelure). That group had an extreme spread of 0.56”.
the control group . .
Three 10-shot groups of the Lake City M855A1 ammunition were fired in a row with the resulting extreme spreads:
1.78”
2.65”
1.78”
for a 10-shot group average extreme spread of 2.07”. 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 30-shot composite group was 0.63”.
The smallest 10-shot group . . .
The 30-shot composite group . . .
M855A1 compared to other mil-spec loads . . .
In the category of useless trivia, the M855A1 bullet cuts the cleanest holes in paper targets of any 5.56mm/223 Remington ammunition that I’ve ever tested. It’s like wad-cutters for the AR-15.
I also fired a 10-shot group at 100 yards off of sand-bags from each of the 14.5” barrels that were used in chronographing the M855A1 ammunition.
A 10-shot group fired from the Colt M4A1 SOCOM barrel had an extreme spread of 1.85”.
A 10-shot group fired from the Bravo Company 14.5" ELW barrel had an extreme spread of 2.15”.
A 10-shot group fired from the 14.5" Hodge Defense barrel had an extreme spread of 2.51".
fired cases
left: from a 5.56 Colt M4A1
right: from a 223 Wylde
Lastly, for any Internet Commandos in our viewing audience today, here’s a pic of a sub ¾ MOA group of the Lake City M855A1 ammunition fired at 100 yards. The group has an extreme spread of 0.59”.
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I absolutely love those barrels, as they always shoot really well for me. I’d be curious to see how a govt. profile M4 barrel would perform in a similar test.
Originally Posted by JediGuy
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