Quote Originally Posted by CrowCommand View Post
Im pretty green to loading for an AR but I've had good luck with IMR 3031. 22.4 grains grouped nicely under a 55gr FMJ at 50 yards in my Mk12. I was trying to develop a blaster/training load (not super focused on accuracy, but cheap and consistent) so I could throw it on the Dillon and crank a bunch out. I've put that on hold now, I can't find any more 3031, and I was caught with my pants down rifle primer wise. I normally just load pistol in bulk. I'm going to focus on precision 77gr loads for the Mk12 now.
3031 is probably not a good powder for a progressive loader. It's stick powder and it doesn't load as smoothly as ball powder. Look for AA2015, AA2230, H335, AA2460, Benchmark is also a good powder.