300 Blackout, Think I got it Arsenal 30 HVTH1 Sliver

[Smk SHoe]

Been fighting with a AR in 300 Blackout. 16" barrel and what seems like a short throat. Have tried RCBS .308-165-SILH, RCBS .308-180-SP, Lee 155, NOE 311-155 HP, and NOE 311-230 FN BLKOUT. Both NOE mold throw great bullets but once PC'd just couldn't get them chambered. Sized to .309 but Ogive was just to far forward. NOE 155's problem was if I seated them to chamber the round was way to short and with the blunt nose they wouldn't start into chamber once cleared from the magazine. So I ordered a Arsenal 170 grain Sliver 30 HVTH1. With the bullet a few thou off the lands, the round is still long enough to feed reliably from factory mags. Now I can at least start load development. 11 plus grains of Lil Gun cycles just fine. Should be able to drop it at least 2-3 grains and still cycle. This AR is just for steel plates and transition drills so long range accuracy is not as important as functioning. Will update monday after torture test Christmas afternoon.

[Moonie]

I believe I mentioned in another thread but the NOE nose sizer in .300 or .301 would probably be just what you need.

[popper]

BO chamber has a long throat/leade. Probably just need to size them smaller - 3085 for mine. The heavy subs end up as bore riders.

[Dadswickedammo]

Have had the same concerns.
I have had trouble with some FMJs and sp in 300bo due to the m-4 feed ramp. Their is some YouTube video on softing or removing one lug.

[Smk SHoe]

Got the ramps softened and cleaned up. Problem was the Noe 155 was seated so deep to chamber that as soon as it cleared the magazine it nosed straight up. Gonna look into the nose sizer before doing anything drastic.