I bought a new RRA 10.5” .458 SOCOM upper a couple years ago, and used it to build an SBR. Between the NFA paperwork, the shortage of components, and my work schedule, I’m just now getting around to [attempt] shooting it.
Long story short, my .458 case rims don't even come close to fitting inside the bolt face.
For the record, brand new Starline brass with the rim measuring .4705”. I have some commercial loads based on Starline brass as well (but obviously a different batch) and they give me the same result.
I removed the extractor just to be sure that wasn’t the issue, and the rim still doesn’t fit into the bolt face. The interior diameter of the bolt face is 0.450", so it's no wonder the 0.470" case rim isn't fitting inside it. Am I missing something obvious, or did I just get an out-of-spec bolt in my upper?
I haven’t attempted to fire a round because I can’t imagine anything good happening, assuming the firing pin can even reach far enough to hit the primer.
Next step?
--Gene