kjeff50cal I have had the same thoughts about rebarrelling a 1911 38 Super to 7.62x25mm on many different occasions. There would be a good many advantages to having a solid piece like a 1911 in that caliber, especially with a good set of sights on it.
Most military pistols however, whether the 1911A1, the CZ-52, the Tokarev or the Broomhandle Mauser, are by their design and sights ill-suited to varmit hunting. The 7.62x25mm cartridge however is not. New loadings commercially available make this old warhorse quite a remarkable caliber. Ron Reed offers a number of loadings and I'm going to try some myself. The cartridges only setback is that those old pistols are the only ones currently chambered for it and without some form of good sights you would be limited no matter what you shot down the barrel. A good set of adjustable sights or even just better sights would really help all those pistols. Maybe some MMCs?
I know that the 1911 has been chambered in the 7.62x25mm, but I don't know how well they worked. The problem I have encountered in stuffing some of the Tok rounds down a 38 Super mag is that the Tok round too long and I can fit only 4 rounds in my 8 round 38 Super mag. Maybe a differently designed floorplate would help a bit but I think the Tok round is just too long. I don't think 10mm mags would work either.
However, all ain't lost. You can rebarrel a 38 Super to the 30 Luger (7.65mm Luger). The Luger round was ballistically limited only by the lower working pressures and sensitivity to ammo of the toggle action the P-08 pistols used. 30 Luger ammo is available but not as widley as the 7.62 Tok. Fiocchi makes 30 Luger as do a few other firms. The bore on the 30 Luger is .310, as is the 32 acp and the 32/20. This gives you ball and softnosed bullet weights ranging from 60 gns (32acp) to 93 gns (30 Luger) to 100 gn (32/20). With proper handloading the 30 Luger can safely be loaded to give near equal performance to the 7.62 Tok, especially in a 1911. I used to regularly hit cans to 100 yds with my old 30 Luger and shot some reloads at a silhouette range and hit the doggone ram. A couple of us were doing that with some oldies. One fella had a P-35 Highpower he rebarrelled to 30 Luger. Believe me, if someone made a new pistol in 30 Tok I would probably be all over it but I do like the 30 Luger and I know that all I need is a barrel to convert a 38 Super.
I think the 357 Sig idea was based more on the 30 Luger than the 30 Mauser. Being based on the 40 S&W, which was being used on a 9mm platform, the bottleneck concept would need to fit the 9mm/40 S&W sized package, and the first bottleneck in that functional length is the 30 Luger. Mikey.