AR-10 accuracy?

[ron]

I did use a case trimmer on these and very, very little crimp. Not sure what I could have done differently, but I was just happy they cycled the action and ejected perfectly.

No crimp. I use standard Full Length RCBS dies for 308---30/06---223 calibers fired in semi auto rifles M1A, M1 and ARs with
no problems. No crimp needed to hold the bullet in place. I have many times tested identical loads with crimp and no crimp.
No crimp is always more accurate.

 

[P7M13]

Ladder test / OCW / grouping tests when reloading.
10+ years ago, before I learned what "velocity nodes" were, I would try to load for the fastest speed that did not exhibit pressure signs. Horrible accuracy. I can go back through some of my notes and see my selection of the fastest powder charge.

 

[Mr Smith]

PSA isn't exactly known for building precision rifles. Just sayin...

But here's the results from one of the 308's I built.


The rifle in the middle did the grouping above. 18" barrel. Both the top two rifles are .308. Haven't gotten a chance to dial in the latest 308 yet (top one with the 24" barrel) as the weather was crap and flooding at the beginning of the year, and covid shutdowns and ammo scarcity for the rest of the year so far.
The bottom one is a 5.56 AR-15.

 

[turbo_vanner]

you have to work up your loads. can't tell if your powder charges are at an accuracy node or antinode for your barrel or somewhere in between until you test a whole spread of charges. I usually start with 0.5gr increments somewhere between what the books say are min and max for a particular bullet/powder combo. Load five of each charge and try to test them slowly and consistently, so barrel temp doesn't affect the later groups. Even leaving a round in a warm chamber for longer than others will also heat up the powder, and create small changes in your groups. I'll run through a few mags in a different gun between every five rounds when i'm doing ladder tests. It takes time, but I don't want to get bad data. Once you find the best group or two, reduce the charge spread from 0.5 to 0.2 or 0.3gr to fine tune your ladder test around those good groups from the first test.

All that said, my AR10 with a Rainer stainless barrel gets about 1.5" with 150gr fmj plinkers and surplus powder and I have done as well as about .80" with 168gr Hornady BTHPs and IMR 4064. Both my loads, and both at least five shot groups.

I've ran through 100 178gr ELD-Ms, and none of my ladder tests were anything near decent. No idea why, and I don't plan on spending the money to find out when 168s seem to shoot fine in my barrel.

 

[Trip Wire]

Stop using heavy pills. Have 2 buds that could not get those barrels to tighten up until they went down to 155gr A-Max.

I spin those 178s at 2880fps out of a 24 inch 30-06 barrel out to 600 yards its boring.

 

[Hummer]

If you have access to a bore scope might take a look down bore after cleaning and see if you have copper build up on the tops of the lands. There are several things you can use to remove the copper build up.