well i been playing around with an old DPMS 5.56 bolt i bought a couple years ago. back when you could get them for $24--LOL
i opened it up to 5.45x39 a couple years back. though the bolt worked OK i never really liked it because i didn't think the base of the round fit 100% flush with the bolt face.
i thought i would open it up a little more to fix this problem and i over did it--it was then leaving 5.46 cases in the barrel.
after giving it a year or so in the "junk box" i took it out today and thought "what the heck?" a couple more turns and it will be opened up to 7.62x39 anyway and if i break the thing --i ain't lost nothing.
about 10 seconds of cutting and a 7.62x39 round fits perfectly! ironically the 5.56 ejector and extractor work perfectly well with the 7.62x39 rounds to boot!
my head-space looks to be a couple .000s more open yet still in the limits.
the only thing it the bolt after being turned and cut looks a shade thinner in the webs than a factory made bolt so it certainly ain't "stronger" by any means--LOL this is due to the "getto/bubba" way i had to cut and open it up.
i did corner the two lugs near the extractor and trimmed the #7 lug a bit shorter.
i am going to test fire it some time today-- LOL!