G21 conversions

[Mack45]

I know that there is a drop in conversion bbl for .400 CorBon but that option is not very appealing to me. Are there any other drop in conversions that I can do with my G21. Does anyone make a bbl for 10mm? I know that I can put a G20 upper on the 21. Any experiences with .400 CorBon?

[green country shooter]

With a 22 pound recoil spring you can shoot .45 Super, though you won't get full benefit of that round without the 6" barrel. Out of the standard barrel the 230 grainer goes about 1100 fps. Texas Ammunition and some others make ammo for it, though you can also reload once you get some cases. The cases are heavier at the base than .45 ACP but have the same dimensions externally. Ammo is available that will kick it on up to 1250 fps, which is pretty hot for a 230 grain, .45 caliber bullet.