Black Hills 5.56mm 77 Grain Tipped MatchKing Ammunition
The Black Hills 5.56mm 77 grain Tipped MatchKing ammunition is loaded with the same Sierra 77 grain Tipped MatchKing projectile that is available as a reloading component (#7177), with the addition of a cannelure. The Black Hills ammunition was actually brought to the market before the reloading component was.
The 77 grain Tipped MatchKing is the longest bullet (that I’m aware of) that is currently being loaded by a major manufacturer to magazine length for the 5.56mm cartridge.
With a nominal length of 1.070”, the 77 grain Tipped MatchKing is 0.335” longer than a 55 grain FMJ bullet and 0.085” longer than the standard Sierra 77 grain MatchKing.
Not only is the bullet itself long, but the ogive section of the 77 grain Tipped MatchKing is also extremely long for a bullet loaded to magazine length in the 5.56mm cartridge; so much so, that the grooves of the cannelure extend into the ogive of the bullet, as evidenced by the “arrow head” shaped cannelure grooves.
In all the time that I’ve been testing and evaluating 5.56mm/223 Remington ammunition, I’ve never seen another load where the grooves of the cannelure extend into the ogive section of the bullet. One has to wonder, what, if any effect this configuration has on the accuracy/precision of the bullet/loaded cartridge.
The Black Hills 77 grain Tipped MatchKing ammunition is loaded in 5.56mm WCC brass has the annealing iris still visible. The primer pockets are crimped and sealed. The case-mouth is crimped but has no sealant. The load is charged with “ball powder.”
I chronographed the Black Hills 77 grain Tipped MatchKing ammunition from a semi-automatic AR-15 with a chrome-lined, NATO chambered 20” Colt M16A2 barrel with a 1:7” twist.
Chronographing was conducted using an Oehler 35-P chronograph with “proof screen” technology. The Oehler 35P chronograph is actually two chronographs in one package that takes two separate chronograph readings for each shot and then utilizes its onboard computer to analyze the data to determine if there is any statistically significant difference between the two readings. If there is a statistically significant difference in the readings, the chronograph “flags” the shot to let you know that the data is invalid. There was no invalid data flagged during this testing.
The velocities stated below are the muzzle velocities as calculated from the instrumental velocities using Oehler’s Ballistic Explorer software program. The strings of fire consisted of 10 rounds over the chronograph.
Each round was single-loaded and cycled into the chamber from a magazine fitted with a single-load follower. The bolt locked-back after each shot allowing the chamber to cool in between each shot. This technique was used to mitigate the possible influence of “chamber-soak” on velocity data. Each new shot was fired in a consistent manner after hitting the bolt release. Atmospheric conditions were monitored and recorded using a Kestrel 4000 Pocket Weather Tracker.
Temperature: 72 degrees F
Barometric pressure: 29.64 inches of Hg
Elevation: 950 feet above sea level
The muzzle velocity for the 10-shot string of the Black Hills 77 grain Tipped MatchKing ammunition fired from the 20” Colt barrel was 2808 FPS with a standard deviation of 14 FPS and a coefficient of variation of 0.50%.
For those of you who might not be familiar with the coefficient of variation (CV), it is the standard deviation, divided by the mean (average) muzzle velocity and then multiplied by 100 and expressed as a percentage. It allows for the comparison of the uniformity of velocity between loads in different velocity spectrums; e.g. 77 grain loads running around 2,650 fps compared to 55 grain loads running around 3,250 fps.
For comparison, the mil-spec for M193 allows for a coefficient of variation of approximately 1.2%, while one of my best 77 grain OTM hand-loads, with a muzzle velocity of 2639 PFS and a standard deviation of 4 FPS, has a coefficient of variation of 0.15%.
I conducted an accuracy (technically, precision) evaluation of the Black Hills 77 grain Tipped MatchKing 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.
All 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 handguards 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 shield was attached to the objective-bell of the scope. 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 Black Hills 77 grain Tipped MatchKing, I fired a 10-shot control group using match-grade hand-loads topped with the Sierra 77 grain Tipped MatchKing (without a cannelure). That group had an extreme spread of 0.68”.
Three 10-shot groups of the Black Hills 77 grain Tipped MatchKings ammunition were fired in a row with the resulting extreme spreads:
for a 10-shot group average extreme spread of 1.26”. 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 0.41”.
The smallest 10-shot group . . .
The 30-shot composite group . . .
The table below compares the test results from this article to previously obtained test data for Black Hills MK262 Mod 1 ammunition, which is loaded with the standard Sierra 77 grain MatchKing (with a cannelure.)
A.E.S = average extreme spread for three 10-shot groups at 100 yards
M.R. = mean radius for the 30-shot composite group at 100 yards
M.V. = muzzle velocity
S.D. = standard deviation of muzzle velocity
C.V. = coefficient of variation of muzzle velocity