Of the bullets you have listed, the Hornady 75gr BTHP is the only bullet I load on my Rock River Arms with a 20" barrel. It is the only one that gave me the best 5 shot results at 200 yards. I tried others , different weights and powders and primers and after extensive research I now only use Hornady's 75gr BTHP with 22.5 gr of RL15. I had a good grouping with 21.7 grains too, but I had a flier and the 22.5 load were all together. At least I know that my node will be between 21.7 and 22.5. This bullet I use for plinking, hunting and target shooting. I like the simplicity of only using this round only on my RRA AR15 which has proven its reliability and accuracy out to 500 yards.
My rifle has the 1/8 twist and when it came to shooting lighter bullets, it did not group them well I tried sierras , nosler, and speers and more from 55 to 69 grainers without much success. I'm glad your rifle likes the FMJ's.
My rifle has the 1/8 twist and when it came to shooting lighter bullets, it did not group them well I tried sierras , nosler, and speers and more from 55 to 69 grainers without much success. I'm glad your rifle likes the FMJ's.
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