The M1 carbine in 7.62 X 25 TOK is an interesting topic. I was contacted a few years ago to make one of my NR barrels (in Stainless steel) for this round. I did not have the correct reamer, and was not prepared to paid the $$ to buy a new one, but did play around with it for a bit. Found the following:
1. Most if not all of this surplus ammo is corrosive, hence the gas hole & chamber in the barrel stub would be very difficult to clean out, and subject to corrosion. I use the USGI barrel stub to accept a sleeved threaded barrel.
2. The TOK round fits quite nicely (staggered) into a std m1 carbine mag, but it will not feed. This cartridge is bottle shaped, as the round slides forward to chamber, as forced by the bolt, it will ride downward following the contour of the round below it. It jams on the feed ramp, and will not chamber.
3. The bolt face of the carbine bolt has to be opened up by about 0.060" dia to allow the base of the TOK round to seat on it. Some tweeking of the extractor is required too.
So, yes cheap surplus 7.62 X 25 is available now, but can this supply be endless?
So, to me, it made more sense economically to pull the 85 gr steel core bullets on the TOK, and reload my .30 carbine cartridge using this bullet (same powder load as the 110 gr.) MV is 2000 fps+