AR 10 pressure question

[hodaka]

I finally found a .260 barrel for my LR-308. It is a DPMS 8.5 twist with a light profile and 20 inch length. I have been working up loads with IMR-4350 and am getting just over an inch at 100 with no issues. Today I tried some IMR-4064. I use a lot of it for my other rifles. I found a load that put five 140 Hornady's into 1/2 inch at 100. The problem is that it will not automatically load into the chamber from the magazine. The empty ejects but the bolt does not travel far enough to catch the next rim. All loads from 32 to 35 grains acted the same. I realize that I don't need to use 4064 but was wondering if a heavier buffer, or even a lighter one, might help this thing to cycle with this powder. Never had any issues with 4064 in the .308 barrel. Thoughts?

 

[Bart B.]

First thing I'd do is shoot a few more 5-shot groups to see if none are larger than 3/4 inch. The one you shot may be the smallest one it'll shoot.

You may be able to go another grain heavier and still shoot those bullets as accurate. Virtually all bullets have a grain or more spread in charge weight that they'll all shoot under 1/2 inch at 100 yards.

 

[hodaka]

I had a heavy T3 carbine buffer from my 6.8 that I installed today in the LR lower. The 4064 ran like a top ejecting every round and locking back the bolt like it is supposed to do. I don't know how it will work over time but the heavy carbine buffer seems to do the trick.