300 blackout

Cast in the .300 BO in an AR is kinda funny. The trip from the magazine into the chamber seems to cause problems. In a .223 carefully hand chambered shoot okay, but from the magazine it’s a different story. I gave up on .223/5.56 cast in AR rifles quickly. I’ve found that in the .300 things are a bit better. A Lee factory crimp die provides better accuracy than a conventional crimper. This also allows you to crimp where you want and don’t have to use the crimp groove. I’m guessing a taper crimp die would work even better. I’ve found that seating cast bullets to just fit in a 20 round aluminum GI contract magazine gives me best accuracy and reliability. Finding a load where the powder is lightly compressed helps too. Keeps the over all length intact through the feeding cycle. My best cast load is with the Lee 230 grain TL BT and A1680 (sub sonic) . Great functioning and 3-4 MOA. Tumbled lubed and loaded as cast. I shoot a lot of these at my mild steel targets with no damage. I still haven’t figured out why one bullet in every 100 to 150 ends up striking thetarget sideways.

My most accurate jacketed load is with W296/H 110 and some old Remington 125 gr PSP bullets I bought years ago for 7.62 x 39. They’ve produce 1.25 inchgroups (and occasionally better) in several .300 rifles and pistols. I crimp them in the crimp groove and they’re pretty short, but function well, probably because the jacket is slick compared to a lead bullet and won’t skid or scratch on the feed ranp