which is preventing me from doing some things I really need to, so I decided to do a little more checking on the .30-30 project idea. Specifically, the bolt, which I thought of as the big problem.
Son called last night, and after other things spoke a bit on this(he's building a .308 AR), and during discussion he suggested check some numbers, which cleared things a bit. Specifically, the first 7.62x39 AR-15 setups used a .223 bolt with the face opened up to hold the wider casehead. A bit of checking gives
.223 rim diameter .378"
So it had to be opened up .069"
So a .308 boltface would only have to be opened up .0332", less than half as much. My, my, that should be doable! Especially since the .308 bolt is set up to handle ~60kpsi, whereas .30-30 has a max ~42kpsi.
So, having heard DPMS has the AR-10 down pretty well, I decided to ask them if they saw any problem with a .308 bolt being opened up that much. That went well:
it will not work as there are no mags or receivers that will let that happen
Why would the receiver not work with it?
the case is too small
I assured them I was not thinking of trying to fire the one cartridge in the other chamber, I'd be using a barrel properly chambered for .30-30.
it will not work
I am a stubborn bastard at times, so I've sent one last question(I promised): since the .30-30 case is the same length as .308, why not? We'll see what they say. I'll have to ask some other manufacturers as well; any suggestions?
Update: that was fast, and disappointing:
the two cases and rounds are completely different
Well DUH!, as daughter used to say, I'd never have noticed that! And that's a singularly uninformative answer, considering the number of different cartridges the AR-10 platform is chambered in.
Other thoughts: I'd probably have to get a barrel bored for .308 and threaded for the barrel extension(I'm learning all kinds of things here) or with it installed, and have the chamber cut so it headspaces properly with the bolt. And a adjustable gas block, because I'm sure that will need fiddling with. Everything except barrel, bolt and magazine would be off-the-shelf parts, and the magazine, I think, would primarily be a matter of adjusting feed lips to work with the cartridge.
I think this is workable(aside from scraping up the money to buy the stuff, of course).