Been doing a little poking around various forums and haven't been able to find much more else about the Russian Enfield. Kevin of Smallest Minority made the very valid point in a comment here that he could just handload a light .303- giving manageable recoil like the 7.62 Russian but with a few hundred extra FPS. It's a good point and anyone not wanting to convert a No. 5 Enfield (the Jungle model) to fire commie ammo could do just that- with the ability to shoot the full power stuff if the need arose. Although the full strength ammo in a Jungle or Tanker model isn't going to be that gentle or quiet to shoot. It's certainly something to bear in mind when considering the conversion. Regardless of calibre I'm now very fond of the Tanker Enfield, whether it's a .303 or 7.62 Russian- that's a very handy looking weapon.
Personally, I don't think that there's a major drawback to switching one of these guns over to 7.62 from .303- the Russian round has enough power to take deer-sized game and it's also proven to be pretty effective against man-size targets too, certainly more so than the 5.56mm. Given the amount of ammo available for the calibre, from cheap surplus to designated hunting rounds, I'd say that there isn't a real advantage to keeping the weapon in .303. The 7.62 Russian has a pretty lousy reputation when it comes to accuracy but that seems to be more to do with cheaply made weapons and poor quality surplus ammo- Gun Mart magazine stated that they were getting 2-3" groups at 100 yards with the AIA M10. That's not too shabby. I'd be interested to see what a full sized No. 4 Enfield converted to 7.62mm Russian could do.