Yes, the magazine well is larger as the .455 magazine is wider. The .455 Webley Auto is a semi-rimmed round, not a rimless like the .45 ACP, so the wider magazine was needed for the larger diameter. The .45 ACP can be fired in the .455, but it will not headspace properly as the .455 barrel has no sharp shoulder and the round has to be held by the extractor.

The .45 ACP barrel will fit in the .455 slide and function OK with either magazine.

.45 ACP magazines are loose in the .455, but a .455 magazine is too tight for the .45 ACP frame. I once mentioned this to a dealer at a gun show who had both a .455 and a .45 on his table. He told me, with a lot of profanity, that I was full of it. He then proceeded to take a .455 magazine ($150 at least!), insert it into the mag well of an M1911 and pound it on the table, bending the loop, until it went in part way. Then he grinned like the idiot he was and said, "See, I told you it would go in." I felt like pounding it on his head to see if it would go in any further.

One small further note. The .455 Webley Auto will fit and fire in .455 Webley revolvers, but it is loaded to much higher pressure. The Britishicon warned against firing it in revolvers, and several Mk VI revolvers have blown with factory .45 ACP cartridges.

I don't know if there is any source in Canadaicon for .455 Auto, but in the U.S., it is in the collector category and very expensive. It can be made from .45 Colt by trimming the case, reducing the rim and cutting an extractor groove.

Jim
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