Originally Posted by
26 Inf
Spent a couple hours late this afternoon doing some shooting to compare MY accuracy with different barrels and triggers.
I took four rifles out:
1) 16 inch Sionics LW Mid-Length (5.56 1:8) BCM Upper, Centurion Rail, MBT 2S trigger, Leupold Mark AR 1.5x4 Scope (this is my wife's rifle, pretty much shot to zero and a couple rounds every now and again)
Rifles 2 - 4 all used the same Burris MSR .223 3x9 scope. I moved it from rifle to rifle, did not zero because shooting for groups.
2) Colt CCU Upper, Colt Lower, Stock Trigger, (I just put this together, the 10 rounds fired through it are the only rounds it has fired)
3) GMB GM-M8 (16" 5.56 1:8 Mid-Length) MI Rail, Geissele SD-E trigger. (this is the rifle I shoot the most, I built it right after attending my first Greg 'Sully" Sullivan srmorer school)
4. GMB GM-M18 (18" .223 Wylde 1:8 Rifle-Length Stainless Fluted), ALG Rail, ALG ACT,
Shot everything at 100 yards, using a Caldwell Tack Driver rest off a concrete bench. No rear support. Ammo used was PPU, 62gr HPBT, 223 Remington Match. I shot 5 round groups so I would have enough ammunition to get through all the rifles.
My intent was to shoot the uppers on lowers with MBT-1S, MBT-2S, Geissele SD-E, and the 'stock' trigger if the rifle wears one. Problem was the lower with the MBT-1S is for a dedicated 22 upper and, therefore, didn't have a carbine spring and buffer. I had H, H-2 and H-3 buffers in my bag, but no springs. The rifles have A5 extensions, except for the Colt, which didn't dawn on me until later. So some don't have 3 trigger groups.
Sionics LW, ML, 1:8 - MBT-2S group 0.644"; MBT-1S group 1.650"
The Sionics had the best group overall, the MBT-1S shots were the first I fired with the MBT-1S, I had one called and one other flyer with this group. These were also the only groups fired at 4 power.
Colt CCU - Stock Colt Trigger: 1.544"; MBT-1S: 1.135"
As I noted these were the first rounds through this upper. The trigger in the stock Colt lower was gritty, it had two distinct grinds before let off, I had dabbed some ALG Go-Juice on the surfaces using a long Q-tip, but nothing else. The MBT-1S managed to surprise me each time it broke.
18" GMB-M21 - ALG ACT: .970"; MBT-2S: .738"; SD-E: .714"
I was pretty disappointed the 16" Sionics and the 16" GMB-M8 both grouped better than this barrel.
16" GMB-M8 - MBT-1S: 1.065"; MBT-2S: .689"; SD-E: .669"
This is a thoroughly broken in barrel, I knew it shot good, but I was surprised at how well it compared.
Overall, I was really surprised with the Sionics, it grouped better than the others, and as noted was shot at 4x while the others were shot at 9x.
I was happy that there wasn't a marked difference between the MBT-2S and the SDE.
Still going to wait before offering opinion on the MBT-1S.
All in all, a fun way to spend a late afternoon, early evening.
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