Yeah, we ran into that once before- it's the 'Cocker barrel adapter that's too tight.
I try to keep the breeches in those adapters fairly 'tight', especially with today's tiny paints. It both helps feed reliability and reduces blowback past the bolt.
However, we've run across a few L10 bolts that are a bit thicker at the swage/braze seam at the tip- not by much, but a few thou adds up when tolerances are tight.
You can send it back to me and I'll either bore it out an extra five thou, or swap it out with another adapter. Or if JB has access to a lathe, he can do it too- it's pretty basic work. (Just make sure he lightly deburrs the inside edges of the feed port afterward.)