Well, gents, I grabbed 500 rounds of the American Reloading 77 TMK to test. The AR 77 TMK ammo came to me in Hornady brass, loose packed 250 rounds to a box. I sent 30 rounds in front of my Lab Radar, which picked up 28. I also fired 10 rounds of generic "Green Tip" with a "P S D" head stamp (don't remember the source). It's 30 deg C and 71% humidity here at lovely Fort Benning, about 450 feet ASL. The rifle is a 16" DD M4V1 purchased in late 2009 with a standard milspec 1:7 barrel and a 5.56 NATO chamber. Below today's data, I'll be presenting historical data taken with an MSv3 in central North Carolina under roughly similar conditions.
20210711:
"Green Tip" - Vavg 2906 fps, SD 20.4 fps, ES 69 fps
AR 77 TMK - Vavg 2565 fps, SD 21.4 fps, ES 78 fps
Historical Data:
PMC M193 (55 grain FMJ) - Vavg 2989, SD 23 fps, ES 82 fps
ZQI M855/SS109 - Vavg 2920 fps, SD 34 fps, ES 98 fps
Lapua 69 grain Scenar - Vavg 2837 fps, SD 18 fps, ES 67 fps
CorBon 77 SMK - Vavg 2529, SD 30 fps, ES 94 fps
Calculations:
Using JBM Ballistics, the AR 77 TMK crosses 1800 fps at ~400 yards with roughly 31 inches of drop on average from a 50 meter zero. The slowest shot recorded was 2522 fps and the fastest was 2600 fps. These would be 33 inches low and 30 inches low respectively.
In terms of trajectory and retained velocity, the 77 TMK compares favorably with the 110 VMax @2600 fps from my 6.8 SPC 16" AR-15. The VMax crosses 1800 fps at roughly 375 yards and drop is funtionally identical at 400 yards. The 120 SST @2440 fps MV crosses 1800 fps at roughly 335 yards.
Wind Drift for the 77 TMK in a 10 mph 3/9 o'clock wind is 15.6". That compares to 17.3" for the 69 grain Scenar or, in the 6.8 SPC, 17.5" for the 120 SST, 17.8" for 110 VMax.
Conclusions:
The 30 rounds tested here for velocity and accuracy functioned without issues and made a neat little brass pile at about the 2 o'clock position. My supposition is that this ammunition is loaded on the light side. The 69 grain Lapua runs ~2840 fps. An 8 grain difference in projectile weight doesn't justify a 275 fps difference in MV. The Black hills spec for Mk262 Mod 1-C is 2750 fps. In terms of quality, I consider it "run of the mill." That is to say that it is similar to ammunition tested from several major manufacturers. It is NOT match grade, regardless of using a "match" bullet. .223/5.56 ammunition in general evidences much higher SD/ES in my testing than 6.8 SPC ammunition.
All shooting was conducted from the prone, off a sand bag (no rear rest) with an Aimpoint PRO. The best accuracy from this rifle has been obtained with the Lapua 69 grain Scenar @ ~1.5 MOA. The M885/SS109 tends to be ~ 2MOA depending on who loads it. The AR 77 TMK was a roughly 3 MOA load today. In my case, the rifle and my performance as a shooter will become an issue well before the performance of the bullet, even from a modest MV of 2565 fps.
