Well, not to dissappoint, or thread hijack, but, I managed to get out again with a somewhat reasonable test with my rifle last night. I too purchased an 18" barrel for my NEA-15 rifle, and after a rough start with some cheap 55 grain, I managed to get it shooting okay last night.
Turns out I'm not that great at shooting prone, and the trigger really is a weak point on this rifle. There's a groove being worn into the trigger face from the sear, which I suspect is why the travel is so rough, and also why I can't tell where it's going to break.
All that aside, it looks like I'm going to focus on 24 grains, using Hornady 75 grain HPBT match bullets.
I know, the groups aren't crazy good, but, I *was* in the zone when I shot #3, and I know for fact that for #5 I was having some poblems holding steady left to right, so, until next week, there you go.... I should also point out that I have another target where the Hornady Steel Match 75 grain shot a group just as tight as #3, so, the gun can clearly shoot better than me.
Also, sorry for the splatter all over the target. I had a smallbore silhouette ram hung right next to the target that I was practicing on with my .22 while letting the AR cool. Next time I won't hang it so close...
Edit.. Groups are at 100 yds, prone, setup as shown. Well, no, the first couple of groups had a rear bag under the stock, but, it's very difficult to get one of these rifles stable for precise shooting.