Boolit diameter vs throat diameter

[Bashby]

I’ve been working on a subsonic cast boolit load for 300 BO in an AR pistol. Barrel slugged at .309, so I sized my boolits to .310. I loaded them way on the long side with a good bit of the .310 part hanging out of the case. This caused the round to not go fully into battery and get stuck in the chamber. I had to mortar it to get the rounds out. Further investigation shows that the throat is slightly under .310 my boolit won’t quite fit. I’m pretty sure I would be safe to seat them deeper, so when chambering the smaller part of my boolit will be in the throat. What worries me with that is when the round is fired, the powder coat will get scraped off as the boolit enters the throat.i have a .309 sizing die ordered, but I’m worried that I will get leading in the barrel.

[cupajoe]

Personally I would pull the bullets and wait for the proper sizer.

[charlie b]

There are some bullets that just do not fit the throats of some barrels.

If you seat them deeper than the book OAL then back off on the load and work back up. You are reducing case volume.

[mehavey]

Seat them to where they no longer jam on chambering.
Proper powder coating will not scrape off at all.
(how do you think it survives Mach+ speeds down the entire length of the barrel?) :bigsmyl2:

[Larry Gibson]

Odds are your barrel is really closer to .308. As mentioned, wait for the .309 sizer and use it. If properly PC'd you shouldn't get leading. PC deposit in the barrel is another story.....