155 Scenars out of 20" AR-10, what can I expect?

[gasdoc09]

I just ordered 200 of the 155 Scenars to try out in my 1:11.25 twist AR-10. (One of the last Armalite SuperSASS rifles before they went to a 1:10 twist.) So far it has liked 168 A-Max handloads best. Consistently 2/3 MOA accuracy if I do my part, and I'm not really that good a shot, yet.

I've shot the 168 A-Max out to 1000y with OK results, hitting steel targets. Tried some 178 A-Max but they didn't group as well as the 168s under 500 yards, and I didn't not ice much difference at the more distant targets.

I've read on this forum that the 155 Scenar bullets are worth trying, since the BC is comparable to much heavier bullets, and they can be pushed faster. But most people seem to e shooting these out of bolt guns with longer barrels.


What kind of MV can I reasonably expect out of a 20" gas gun?

Recommended powders? I have a ton of Varget and some AR Comp, but am not opposed to scrounging up something different. Thanks.

 

[poison123]

Probably 2700's maybe...maybe into the low 2800's if you really push a hot load.

 

[gasdoc09]

Probably 2700's maybe...maybe into the low 2800's if you really push a hot load.

Thanks.

I did some more searching and found this great pdf by Bryan Litz that has some great info in the "Fullbore Bullets in Service Rifles" section.

Mid 2700s looks achievable, with the 155 Scenar staying supersonic to 1000y, probably, but just barely. Looking forward to trying them out.

 

[bm11]

I haven't chronographed the load I worked up to, but my SR-25 shot the same load as my bolt gun- 46.5 grains of Varget in a Lapua case at 2.860" COAL. Keep in mind that a PMAG will not feed a cartridge that long but a SR-25 mag will.

The load I listed should be too hot for a gas gun (work up WAY lower as your experiences may vary) but don't show any more pressure than in my bolt.

Can't tell you what it chrono's out of my 20" SR, but it hits 2825 FPS out of my 18.5" AIAX.