If I was doing a build I’d probably convert a 9mm carbine of some kind. A JR carbine for example get a 308 barrel blank machine it to fit and chamber it. Considering how easily tokarevs can be converted back and forth I’m guessing similar bolt thrust so the blow black system may work or may not. Given 7.62x25 uses a lighter bullet it may have less in which case the bolt could be lightened. The mag wells could be changed out to a custom one or you may be able to alter a 9mm to work with a tok mag. My concern with the m1 carbine is the gas system, I’m guessing 30 carbine has a different pressure curve so some alterations then also I’ve never cleaned an M1 but corrosive ammo can be harder on some gas systems depending on ease of cleaning every little spot. I’ve also heard that USA specified non corrosive ammo for the M1 carbine? Not sure reason or legitimacy of this claim? Either way whatever you build, love to see it, I’m currently building a bolt action in 7.62x25
It would take a lot more work
9mm magazines aren't long enough and you would have to find other mags, such as TT33 mags to fit to the receiver, which would have to be modified to accept them.
M1 Carbines, such as the Auto Ordnance work just fine. Their only drawback is that they're gas operated and cleaning can be a chore with corrosive surplus ammo.
I converted one, after looking at one in Lever Arms.
I was going to buy one of the few Lever Arms brought in but was turned off by the condition.
My rifle operated without issue after the conversion.
As for a castle type gas nut wrench, they're easy to make and cheap. Be careful though, because some of them are pinned in place.
If you purchase one of the Criterion non restricted barrels, it's pretty easy to take them down and clean properly for corrosive ammo.
The only real reason I can see for the conversion is to utilize the cheap surplus ammo, which isn't that cheap any longer.
When my stock of ammo ran out, just over 15k rounds, I pulled that barrel, which was well worn and put on another 30M1 barrel.