The M1 carbine is my personal favorite hunting & plinkin' rifle, but because of the constant threat of
reactionary retards to prohibit or confiscate these from rightful owners, I no longer own one.
If I were to do a build-up one of these, the best cartridge to chamber it for is the 7.62x25 Tokarev/.30 Mauser.
The 9mm. Para is not in my radar as it is too short for reliable feeding and not as accurate at 100yds. as the Tok.
If Winchester had their act together back when they were working with "Carbine Williams" to get this rifle into
service, then we would have 'em in a great all-round chambering....the .351 Winchester SL.
There definately would not have been many complaints about stopping power using this chambering on enemies using a 160 gr., truncated cone FMJ boolit. A minor lengthening of the action & magazine would have done
this perfectly, with only an extra couple of ounces in weight gain.
Why those goofs went with a cartridge based on the .32 SL is beyond me. Politics strike again I guess.

Typical of U.S. policy.