A. INTRO:
I finally got my LMT 5.56 Piston Upper on 1-2-09 and I had the chance to take it to the range on 1-3-09. I'm not going to bore you with pictures or tell you how clean the upper was or how cool the BCG was to the touch after several hundred rounds. I think most of you guys already know the benefits of a Piston AR. What I have always wondered was the accuracy of a Piston AR. This is my very first Piston AR. The one thing that I have always wondered about the Piston AR's was the accuracy. Everytime someone asked a Piston owner about the accuracy of their AR, most of the replies were, "This is a Combat Rifle." So I decided to test it out myself.
B. 16" LMT 5.56 Piston Upper:
1. Brief Description:
16" Chrome Lined Barrel with a 1:7" Twist. Midlength Piston System.
2. Break-in:
Before going out, I checked the Chamber with the PTG 5.56 Reamer to make sure that it was indeed a true 5.56 Chamber, which it was. I then polished up the Bore with some Remington cleaner. I broke in the barrel with the Tubbs Final Finish Bullets (Sierra 77 Gr. SMK Bullets). In the first 30 bullets, I had approximately 10 Short Strokes, which was not a surprise since I used a very light load with H322 with the 77 Gr. SMK Bullets. The remaining 20 bullets used during the break-in period all feed fine.
3. Accuracy Results:
Support Used: Harris Bi-pod and rear sandbag.
Optic: Swarovski Z6i 1x6 scope set on 6x.
Trigger: WOA Tuned RRA with Superior Shooting Springs.
Range: 100 Yards.
Shot Groups: 2 10 round shot groups.
Hornady 55 Gr. FMJ:
Brass: Winchester.
Primer: Wolf Smal Rifle Magnum.
Crimp: Lee FCD.
OAL: 2.220".
Temp: 30. (70 during chronoing.).
24.5 Gr. of X-Terminator: Avg: 2885 fps, Lo: 2861 fps, Hi: 2911 fps, ES: 50, SD: 21
ACCURACY: 1.823"
25 Gr. of X-Terminator: Avg: 2954 fps, Lo: 2898 fps, Hi: 2982 fps, ES: 84, SD: 33
ACCURACY: 1.945"
25.5 Gr. of X-Terminator: Avg: 3005 fps, Lo: 2982 fps, Hi: 3023 fps, ES: 41, SD: 19
ACCURACY: 1.903"
25.5 Gr. of Benchmark: Avg: 2965 fps, Lo: 2936 fps, Hi: 2989 fps, ES: 53, SD: 19
ACCURACY: 1.307"
26 Gr. of Benchmark: Avg: 3021 fps, Lo: 3005 fps, Hi: 3089 fps, ES: 41, SD: 20
ACCURACY: 1.335"
23 Gr. of H322: Avg: 2761 fps, Lo: 2726 fps, Hi: 2789 fps, ES: 63, SD: 23
ACCURACY: 1.095"
23.5 Gr. of H322: Avg: 2826 fps, Lo: 2772 fps, Hi: 2855 fps, ES: 83, SD: 32
ACCURACY: 1.922"
25.5 Gr. of H4895: Avg: 2891 fps, Lo: 2849 fps, Hi: 2943 fps, ES: 94, SD: 34
ACCURACY: 2.531"
26 Gr. of H4895: Avg: 2985 fps, Lo: 2949 fps, Hi: 3023 fps, ES: 74, SD: 26
ACCURACY: 1.585"
26.5 Gr. of H4895: Avg: 3049 fps, Lo: 3016 fps, Hi: 3079 fps, ES: 63, SD: 24
ACCURACY: 1.978"
25.5 Gr. of Varget: Avg: 2784 fps, Lo: 2721 fps, Hi: 2855 fps, ES: 134, SD: 56
ACCURACY: 2.015"
26 Gr. of Varget: Avg: 2859 fps, Lo: 2842 fps, Hi: 2892 fps, ES: 50, SD: 20
ACCURACY: 1.413"
26.5 Gr. of Varget: Avg: 2928 fps, Lo: 2898 fps, Hi: 2969 fps, ES: 71, SD: 31
ACCURACY: 2.423"
Hornady 55 Gr. FMJ:
Brass: Winchester.
Primer: CCI #41.
Crimp: Lee FCD.
OAL: 2.220".
Temp: 80.
25.6 Gr. of Benchmark: Avg: 3124 fps, Lo: 3115 fps, Hi: 3137 fps, ES: 22, SD: 11
26.5 Gr. of Benchmark: Avg: 3180 fps, Lo: 3152 fps, Hi: 3205 fps, ES: 53, SD: 18
ACCURACY: 2.170"
26.5 Gr. of H4895: Avg: 3115 fps, Lo: 3093 fps, Hi: 3137 fps, ES: 44, SD: 22
25.5 Gr. of TAC: Avg: 2929 fps, Lo: 2904 fps, Hi: 2943 fps, ES: 39, SD: 16
ACCURACY: 1.688" (5 Rounds).
26 Gr. of TAC: Avg: 3002 fps, Lo: 2982 fps, Hi: 3023 fps, ES: 41, SD: 20
ACCURACY: 1.813" (5 Rounds).
26.5 Gr. of TAC: Avg: 3072 fps, Lo: 3051 fps, Hi: 3093 fps, ES: 42, SD: 18
ACCURACY: 1.599" (5 Rounds).
27 Gr. of TAC: Avg: 3107 fps, Lo: 3090 fps, Hi: 3122 fps, ES: 29, SD: 13
ACCURACY: 2.032" (5 Rounds).
Hornady 75 Gr. BTHP:
Brass: Winchester.
Primer: Wolf Smal Rifle Magnum.
Crimp: Lee FCD.
OAL: 2.250".
Temp: 30. (70 during chronoing.).
22 Gr. of H322: Avg: 2558 fps, Lo: 2520 fps, Hi: 2583 fps, ES: 63, SD: 25
ACCURACY: 1.119"
22.5 Gr. of H4895: Avg: 2420 fps, Lo: 2406 fps, Hi: 2428 fps, ES: 22, SD: 8
ACCURACY: 1.122"
23 Gr. of H4895: Avg: 2450 fps, Lo: 2424 fps, Hi: 2487 fps, ES: 63, SD: 24
ACCURACY: 1.701"
23.5 Gr. of H4895: Avg: 2525 fps, Lo: 2501 fps, Hi: 2549 fps, ES: 48, SD: 22
ACCURACY: 1.517"
23 Gr. of Varget: Avg: 2395 fps, Lo: 2372 fps, Hi: 2420 fps, ES: 52, SD: 21
ACCURACY: 1.537"
23.5 Gr. of Varget: Avg: 2477 fps, Lo: 2460 fps, Hi: 2492 fps, ES: 32, SD: 11
ACCURACY: 1.306"
24 Gr. of Varget: Avg: 2524 fps, Lo: 2510 fps, Hi: 2544 fps, ES: 34, SD: 15
ACCURACY: 1.704"
Hornady 75 Gr. BTHP:
Brass: Winchester.
Primer: CCI #41.
Crimp: Lee FCD.
OAL: 2.245".
Temp: 80.
22.5 Gr. of Benchmark: Avg: 2683 fps, Lo: 2666 fps, Hi: 2704 fps, ES: 38, SD: 16
22.8 Gr. of Benchmark: Avg: 2690 fps, Lo: 2666 fps, Hi: 2710 fps, ES: 44, SD: 20
23.1 Gr. of Benchmark: Avg: 2705 fps, Lo: 2682 fps, Hi: 2737 fps, ES: 55, SD: 22
24 Gr. of H4895: Avg: 2704 fps, Lo: 2661 fps, Hi: 2737 fps, ES: 76, SD: 39
Nosler 77 Gr. BTHP:
Brass: Winchester.
Primer: CCI #41.
Crimp: Lee FCD.
OAL: 2.245".
Temp: 80.
22.5 Gr. of Benchmark: Avg: 2650 fps, Lo: 2629 fps, Hi: 2682 fps, ES: 53, SD: 21
22.8 Gr. of Benchmark: Avg: 2656 fps, Lo: 2635 fps, Hi: 2682 fps, ES: 47, SD: 18
23.1 Gr. of Benchmark: Avg: 2691 fps, Lo: 2677 fps, Hi: 2699 fps, ES: 22, SD: 9
24 Gr. of H4895: Avg: 2699 fps, Lo: 2682 fps, Hi: 2732 fps, ES: 50, SD: 22
Sierra 77 Gr. SMK:
Brass: Winchester.
Primer: CCI #41.
Crimp: Lee FCD.
OAL: 2.245".
Temp: 80.
22.8 Gr. of Benchmark: Avg: 2668 fps, Lo: 2645 fps, Hi: 2682 fps, ES: 37, SD: 14
23.1 Gr. of Benchmark: Avg: 2685 fps, Lo: 2661 fps, Hi: 2710 fps, ES: 49, SD: 21
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Factory ammo:
Hornady 60 Gr. V-Max TAP-FPD:
Avg: 2777 fps, Lo: 2766 fps, Hi: 2789 fps, ES: 23, SD: 11
ACCURACY: 1.528"
Hornady 75 Gr. BTHP TAP-FPD:
Avg: 2554 fps, Lo: 2525 fps, Hi: 2574 fps, ES: 49, SD: 18
ACCURACY: 3.021"
HSM (Hunting Shack Munition) 60 Gr. V-Max:
Avg: 2678 fps, Lo: 2645 fps, Hi: 2704 fps, ES: 59, SD: 23
ACCURACY: 1.402"
HSM (Hunting Shack Munition) 69 Gr. SMK:
Avg: 2574 fps, Lo: 2559 fps, Hi: 2588 fps, ES: 29, SD: 11
ACCURACY: 1.697"
M193:
Avg: 3127 fps, Lo: 3108 fps, Hi: 3152 fps, ES: 44, SD: 18
ACCURACY: 2.346" (7 rounds)
4. Conclusion:
1-3-09: So far, I have only had the 10 Failures which were during the break-in. I believe those were due to the weak loads and not weapon or magazine related. I'll keep updating as I do more accuracy testing in the upcoming days. So far, the accuracy is OK. Recoil is typical of any 5.56 AR that I've shot. The recoil with H322 was practically nill. I did check for Carrier Tilt and did observe some marks inside the buffer tuber, which I checked prior to shooting and there weren't any. It does not seem bad at all, but I'll keep an eye on it. I also noticed that the oprod is slightly bent. I'll call up LMT and ask them about it.
1-5-09: The carrier looks the same, so it looks like the carrier tilt has leveled off. I spoke with LMT today about the bent oprod and they said it is normal. So far I am very impressed with the accuracy.
1-15-09: Total of approximately 1K rounds so far with no problems.
