I recently built a 300 blk with a core15 9.5" barrel (awesome barrel BTW) and have been experimenting on some loads for it. I am making my own cases by cutting down 223/5.56 brass and I have a crap load of 170 grain 30 cal round lead nose made for a 30-30. I read where it wouldn't work on an AR because the round nose would get caught on the feed ramps etc, but I like to test instead of just regurgitating internet folk lore, so I grabbed a couple of pounds of H110 and got to work. I started quite light (yes, I know the dangers of reduced load H110, but then again, if you don't use your brain, then reloading is probably not for you anyway, so YMMV, use at your own risk, etc etc) I started off with 8 grains of H110 with an OAL of 2.10. It fired the bullet all the way through the barrel (no squibs) and ejected the case, but would not lock the bolt back (when experimenting, I ALWAYS) fire one cartridge at a time. So I increased .5 grains at a time until I hit 11.5 grains. At this point, I started getting a locked back bolt. I continued increasing it until I reached 15 grains and will probably stop here. I have not chrony'ed it yet, but it fires every round, ejects, strips the next one and locks back on the last round and I have no pressure signs or flattened primers. I am pretty certain that I am still subsonic, but won't know until I can properly chrony it. I think that this might be a useful hunting round since the lead nose wouldn't depend as much on velocity for expansion as most of the 308 rounds currently do, so the shorter barrel and reduced speeds of the 300blk should not be an issue. Anyway, this is my story and just figured that I would share.