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.
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”.
Chronographing of the IMI M855 ammunition was conducted using an Oehler 35-P chronograph with “proof screen” technology. All velocities listed below are muzzle velocities as calculated from the instrumental velocities using Oehler’s Ballistic Explorer software program. All strings of fire consisted of 10 rounds each.
Each round was single-loaded and cycled into the chamber from a magazine with a single-load follower. The bolt locked-back after each shot allowing the chamber to cool in between each shot. Each new shot was fired in a consistent manner after hitting the bolt release. This technique was used to mitigate the possible influence of “chamber-soak” on velocity data. Atmospheric conditions were monitored and recorded using a Kestrel 4000 Pocket Weather Tracker.
Atmospheric conditions:
Temperature: 75 degrees F.
Humidity: 47%.
Barometric pressure: 29.97 inches of Hg
Elevation: 950 feet above sea level
Two different barrel lengths were used in obtaining velocity data; a 14.5” Colt M4A1 barrel and a 20” Colt M16A2 barrel. Both barrels have NATO chambers, are chrome lined and have 1:7” twist rates. Both barrels have low round-counts on them.
