I had a partial case head separation using a 1.8oz buffer

[pashiner]

case neck dimensions are critically important. I learned this 2 years ago by blowing up a 300 blackout. I had worked up a good subsonic load with a cast lead bullet, and started forming brass from .223 range pickups. My load (7.2 gn Lil Gun) was just hot enough to cycle the action smoothly (pistol length gas, 16" barrel, std buffer and spring) but a case with a slightly thick neck snuck it's way into my magazine. It chambered, fired, extracted and ejected ok...but tore the lugs out of my barrel extension. left me a cute little 300blk belted magnum case in the brass catcher as a souvenir.

"if it seats, it yeets" is bad advice...even with those little pipsqueak loads!