A little brainstorming, if ya'll don't mind. I've read more than a few times about folks wishing the M1 was chambered in 7.62x25mm. I don't know how well that would work as the 7.62x25mm is approx. the same, powerwise, as the .30 Carbine. It did get me to wondering though. Why not a shortened .300 Whisper? According to my math, a .300 Whisper with the neck shortened to create a 1.26" case and loaded with the 125gr Sierra HP-FN will have approx. the same overall length as the .30 Carbine cartridge. The neck length should wind up being very close to that of a 7.62x25mm or .30 Mauser. The reamer should be very inexpensive since the only difference is the shorter neck. Case forming dies for the .300 Whisper are easy to get as are neck sizing/crimp dies for the 7.62x25mm. No custom (ie. expensive) dies are required and brass is very inexpensive. Powder charges should be easy to extrapolate from existing .300 Whisper data. You can't use the longer/heavier bullets because they won't fit, but you shouldn't anyway because the M1 has a 1:16 twist and wouldn't stabilize them. The power increase should be considerable, possibly even equalling the .30-30 Winchester, .30 Herrett or 7.62x39mm.