Originally Posted by
Jim in Salt Lake
I would stay away from those 155gr Palma bullets with a ten twist barrel. As you found, the 168s and up work better with that twist rate. Most Palma shooters use 12 or 13 twist barrels with 155s. The reason Palma loads are so hot is that they're trying to keep the bullet supersonic at a thousand yards. That's a lot easier to do with the bigger bullets, the Palma rules specify 155s to make it hard in my opinion. If I got an AR10, I'd go looking at M1A/M14 loads that were used before the AR took over Service Rifle competition. I used to shoot 168s over 40.5 gr of IMR 4895. Loads of IMR 4064 or Varget would work just as well, too, all are great powders.
I have a target rifle I made out of a 1903A3 with a McGowen heavy 1/10 twist 26" 30-06 chambering. It shoots the 150 Sierra and 155 Palma's to a 1/4" at 112 yards. That's using Varget, 47 gr. I also shoot a Hornady 125 Gr. SST using Imr 4064, 48 gr. and those will do 3/16" 5 shot groups at 112 yards. I'm a little puzzled those wouldn't shoot rather well in .308. Lately I'm working on the upper end with the 175 and 178's and getting 3/8 to a 1/2 with those using 46.4 gr again, Imr 4064. Seems odd that this rifle likes both ends and almost equally well. Longer distances I haven't tried yet as our local range is limited to the 112. There is one up the highway and I'll take a couple trips up there this summer and see how it does out to 300. I'm also in the process of making another target rifle out of a SC in .308 so looking forward to that.
As the late Turner Kirkland was fond of saying, "If you want good oats, you have to pay the price. If you'll take oats that have already been through the horse, those come cheaper."