Since the OP already has the barrel, ammo, and dies, I'll tell him to enjoy the experiment.
But make damn sure the bullets don't set back in feeding, after you get them seated, because the fun will then be over.
The interesting thing is, you can load a .400CB down say 135's at subsonic speed, and it will still run fine. It's a fairly neat and inexpensive way to reduce the recoil of a .45 cal 1911. But do your research carefully as there a lot of subtle things about getting the .400 CB to run reliably.
Last edited by tex_n_cal; 04/05/15. Reason: last sentence
