I have used the 223 77smk from Black Hills and they group nicely. I went to reorder and noticed there is also a 556 77SMK from Black Hills??

They both have 2750fps listed. so what are the differences? I know normally 556 has higher pressure, but these have the same bullet and run the same speed.

The ammo is expensive, so dont want to buy the 556 and realize the 223 shoot better.

Does Black hills ever go on sale??

Thanks

The 5.56 is measured with a 20" Barrel while the .223 is from a 24" Barrel. So the 5.56 is a bit hotter maybe by 100 FPS tops. (20" vs 20")

Can't say I've ever seen it on sale.

If BH ammo goes on sale... it is rarely.

I suggest you buy one of each ( include the 77gr TMK ) and see which one your rifle really likes.

Each of my rifles have distinctive preferences ammo accuracy wise.

What distance do plan on shooting these ?

There are accurate, cheaper choices if you are shooting 100-200yds for accuracy practice.

The only "sale prices" I have ever seen were from Old Virginia and or Triad Tactical.

They generaly follow the .223 and 5.56 pressures for those respective designs, so if you try them in the same rigs you should expect to see some difference.

Black Hills states on their website that this load has a velocity of 2750 FPS, but they do not state an associated barrel length with that. From a 20” Colt barrel this load had a muzzle velocity of 2687 FPS with a standard deviation of 16 FPS.






Black Hills MK262 Mod 1





The 77 grain MK262 ammunition produced by Black Hills Ammunition has been referred to as the most accurate mass-produced 5.56mm ammunition that has ever been type-classified and issued by the US military.  Since its inception, genuine MK262 has been manufactured solely by Black Hills Ammunition.  For years, MK262 was only available to the civilian population as “seconds,” but more recently Black Hills has made first-run production lots available on the commercial market.  It is the first-run version of MK262 Mod 1 that I tested for this report.

MK262 Mod 1 is loaded in WCC 5.56mm brass and uses a cannelured version of the 77 grain Sierra MatchKing.  The round is charged with a proprietary ball powder.  The primer pockets are crimped and sealed.  Contrary to erroneous information that has been posted on the Internet, MK262 Mod 1 does not have case-mouth sealant.















The 77 grain MK262 Mod 1 projectile compared to the M193 projectile.







MK262 powder.  (The squares of the red grid measure 1/10 of an inch.)






I chronographed the Black Hills 5.56mm MK262 Mod 1 ammunition from a semi-automatic AR-15 with a chrome-lined, NATO chambered 20” Colt M16A2 barrel.









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 has its onboard computer analyze the data to determine if there is any statistically significant difference between the two readings.  If there is, the chronograph “flags” the shot to let you know that the data is invalid.  There was no invalid data flagged during this testing.

The velocity stated below is the muzzle velocity as calculated from the instrumental velocity using Oehler’s Ballistic Explorer software program. The string 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.









Atmospheric conditions

Temperature:  79 degrees F
Humidity:  37%
Barometric pressure:  30.12 inches of Hg
Elevation:  950 feet above sea level


The muzzle velocity for the 10-shot string of the Black Hills 5.56mm MK262 Mod 1  ammunition fired from the 20” Colt barrel was 2848 FPS with a standard deviation of 10 FPS and a coefficient of variation of 0.35%!

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 (and to give you an idea of how good the CV is for this factory loaded MK262 Mod 1 ammunition) 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%.









….

THANKS!


guess I am still going to have to test more types.

I did notice the 223 77smk reman BH shot just as well.


I will order some BH 556 77smk in red box and blue