**Update**
Got to the range today to do some accuracy testing and see how it show the 2nd 100rds of ammo. It was flawless through another 90 rounds using 7 different ammo selections from 147 to 175.
The way I did it was I started with the stock rifle and did a 5 shot group of every ammo, then changed the buffer tube/spring/buffer out to the armalite setup and shot a 2nd 5 shot group of every ammo.
Keep in mind, I don't have a ton of time behind a large frame gasser and I'm using a Burris RT-6. Wind was blowing 90* from 10-20mph, so it's possible some group variation was the wind gusts. I did watch some of frank's large frame gasser videos, so I just tried to keep it consistent, follow through, and get a good NPA.
The ammo shot for groups was:
1.) Korean M80 surplus
2.) American Marksman Reman'ed "M80"
3.) PPU 168gr (not shown, 2-3 moa)
4.) Federal Fusion 150gr
5.) Federal Match 168gr Berger
6.) Federal Match 175gr SMK
7.) M118 (also 175smk I believe)
One interesting note is both 175gr ammo would not fully cycle at the current gas setting. I had to open the gas block up 2 clicks to feed the 175's correctly.
The Federal 168 Berger "felt" like the heaviest recoiling ammo I shot. I did not get chrono data but hope to next time.
Korean M80 - Both groups were right around 2.5-2.75moa Reman. M80 - Basically the same as the Korean M80 (2-3moa)
Federal Fusion 150gr. -- Smallest group of the day at 0.8moa. But also biggest group at 1.6moa. May have been me on the first group
Federal Match 168gr Berger -- I thought this may have been the best, but fell right into the "average".
Federal Match 175gr Sierra Matchking -- I felt overall, the 175's performed the best. The first group was when I found out the gas setting was quite right. I shot two, adjusted the the gas, then shot 3. Probably my fault.
M118 (LC04) -- Shot better than I thought, but then again I have no experience with M118. 2nd group, 5th shot was called flyer. That group was shaping up to be pretty good too.
In the end, I thought it was pretty decent for what it is. With match ammo, it's easily a 1-1.5moa rifle. I think with a better shooter, some tuning or maybe handloads, it'd be a solid 1 moa shooter.
The buffer change mid session did result in a little better average group size, not that I would attribute it to that entirely. After a few groups, I felt more comfortable, but then again, the last groups start to wear on you. Recoil impulse change was noticeable. Recoil felt more drawn out, and not so snappy, which I figured would be the case. Ejection pattern direction was the same for each ammo type, however the distance travelled was less after the buffer change. Ejection went from about 10-15ft to around 7-10ft.
This reaffirms the idea that an AGB is not the ONLY thing to be adjusted to make a rifle shoot better/smoother. This seems to be especially true on large frame but applies to small frame as well.
**Side Notes -- This milspec PSA trigger is pretty nice...that is compared to other milspec triggers. Very surprised how well it did in a precision setting. I could easily say its only a little heavier and "worse" than the original Geissele SSA (4.5lbs)
The American Marksman M80 Reman'ed ammo is super cheap, comes bulk packaged, and is dirty ammo...as if it was never tumbled. However, it does come with LC brass and it performed just as well as the other surplus M80 I had did. So I'll probably buy more, and might try their M118 reman'ed. I did have one case blow a case head on me though, 3 shots into the day. Thought my magazine caught fire cause it was smoking so bad. First time for that ....
