I jumped on the .300 BO thing several years back. Loaded up some ammo, went to the range a few times, had some issues (some people say they use pistol primers but I won't use them anymore) with perforated primers, failure to function and poor accuracy.
I stopped using pistol primers, I found some loads with a couple different powders that functioned correctly in an AR15. I never was happy with the groups.
The rifle was cleaned/lubed well, put in a case and set in a corner for a couple years till I pulled it out and removed the lower for a .223 build.
I'm working on all this brass for a .300 BO pistol my youngest son has. He's hoping for better accuracy, he's hoping the Hearing Protection Act gets passed. He's planning on knocking down a deer or two behind his house with it, quietly.
He's going to get all my brass and the powder I bought for the cartridge and he can work on it (getting it to work, getting it to shoot groups he's happy with.)
My "short" .30 is a SIG 556R. I get better groups from it with Wolf FMJ or HP than I ever got from the AR15 in .300 BO.