[SCPO]

can i use different cal. barrels in this gun. i've got a bunch of 9mm i would like to shoot.

[JR]

No, a 9mm conversion barrel in the G21 would fail because:
1) The 9mm is way to weak to reliably cycle the gun
2) The slide breach face is way to big to accommodate the 9mm case

[SCPO]

any other barrel fit. caliber

[JR]

The only G21 conversions we offer are the 40 Super http://bit.ly/qyN4Ri or 400 CorBon http://bit.ly/rqZAcd.

[SCPO]

Originally Posted by jr

the only g21 conversions we offer are the 40 super http://bit.ly/qyn4ri or 400 corbon http://bit.ly/rqzacd.

40 super not same as standard 40 is it. Not familar with it. Is ammo readily available.

[JR]

You are quite correct, 40 Super is NOT the same as 40 S&W (not even close). A 40 Super is actually an improved 45 mag case necked down to accept 40 cal bullets. Its a smokin' hot 40 round! FYI: it is 50 to 200 fps faster than the 400 Corbon. The 400 CB is a standard 45 ACP case necked down to accept a 40 bullet.
YES, 40 Super can be found at Double Tap Ammunition. 400 CorBon can be found at Corbon. Tell 'em JR from LWD sent ya