Not new to shooting, ARs or reloading, but last year, on a splurge, I bought a .450 BM upper, Dies and Brass. I have loaded .414 SM with LilGun, and a lot of other cartridges. Finally got the time to work on it some this winter.
I bought some single shot followers and made my own magazines, 2 each out of 30 and 40 round metal magazines bodies, all worked perfectly. I machined a .45ACP case bushing for the Dillon 650 and put together my own "conversion kit." Works like a charm. For my load development, I started with a 230 grain JHP, CCI41 primers and 25 grains of LilGun. I was totally shocked that it actually ran the rifle with a MV of 1560 fps. Case was a tad smoky, no signs of anything being off at all. Worked up to 36 grains for a MV of 2153 fps. When I hit 32 grains, each round resulted in the mag ejecting. Considered putting another turn on the mag catch since I run them barrely engaged normally, but decided to switch lowers and go from a Cavalry Arms lower with a Carbine length buffer tube to a LAR lower with a rifle length buffer tube and a JP XP recoil spring. Totally changed the feel of the recoil impulse and no more ejected mags.
Running a Burris 332 3x red/green illuminated reticle for an optic. Just got my comp from Ross and plan to install that tomorrow and then run some more rounds this weekend. Depending on what I find, I may go try adjustable gas. I'm making an adapter to put a Carbon Fiber 14" long handguard on it so I don't have to hold the gas block anymore. Have not really done any accuracy testing yet. The .450 BM sure is a fun to shoot.