Problem is, that unless you have a removable pilot reamer, the .312 pilot will not fit in a 308 bore, so the reamer can't cut a chamber in one. Other thing is that the .303 barrels have really fat wide lands, 5 of them which makes them real happy with cast bullets. The best of all of these is the 32-20, the case shape is less prone to sticking than the real long .327 Federal or even the 32 H&R Mag. The 30 Carbine is nice but does not have a rim, so it is not as easy to do in a Handi. Also, 30 carbine rounds have case lengths all over the block, the longest is about .010 under the SAAMI spec, others are even shorter, because they seat on the case mouth this is a problem, if you cut a SAAMI spec chamber you will have excess head space. Because they seat on the case mouth you can't use a roll crimp on them and even a taper crimp causes head space problems. A 30 carbine cut a little short is very nice to shoot and will shoot subsonic 180gr cast with about 8 or 10gr of 1680 as I recall, (you might want to check that). Larry