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

Did you buy the upper directly from RRA?  If so, please contact me (IM/e-mail/call) with the order info (or even your contact info) and I can look up the order.  I don't know how it would happen with a factory upper, as we would have to have shot it, but I can't rule anything out until I have more information.
If not directly from us, I would assume that whomever you bought it from didn't provide the proper bolt with the upper.
Thanks.
Steve/RRA

Bought it at a gun show from M&A Parts, so sounds like I need to contact them, though I'm skeptical they will address the issue this far down the road.

So, looks like this project is going to cost me some more money.  I see you guys have .458 SOCOM bolts on the website for $160, which leads to the following queries:

1)  Can I assume that this is a "drop in" replacement, or do I need to worry about headspacing?

2)  Are these bolts currently available, or back-ordered indefinitely?

3)  The bolt carrier on this upper is stamped "RA" on the side.  Is that one of yours, or did the bolt and bolt carrier both get swapped out with who knows what?

Thanks, Steve!

--Gene

Sounds like you may have had a carrier group swap at some point.
Try M&A first and see if you have any recourse there.  Let me know and I'll try to get you squared away if they can't/won't.

You always need to head space a bolt to the extension that you're going to use it with.  A lot of "technical gurus" with about five builds under their belt will tell you that you can just throw any new bolt with any new barrel and you're good to go.  They are dead wrong, and lucky to not just be dead.  They may be correct 9999 times out of 10,000...but you don't want ot be that 1 in 10000 that may grenade when used because of dangerous headspace.

Thanks.
Steve/RRA.

Talked to Andy at M&A, and he said he thinks they can swap me out bolt and carrier if I have the receipt (which I should, but I'm at work right now).  

I'll try going that route, and buy myself a set of headspace gauges just to make sure the swapped out parts still get along with my barrel.  If I need your help, I'll get back in touch.

Thanks, Steve!

--Gene