Basicly the question is, is it safe? The MkV & MkVI had a larger/heavier cyl. intended for modern ammo and a great many were converted to .45ACP (quite safe, no problem)

Lots of MkI - MkIV's conversions however are on the market that were originaly intended for BP and/or cordite. Now I've never heard of one blowing up with std. pressure factory .45ACP ammo. But is it really a good idea to shoot them with it?

The MkI I have has had a lot fired through it. (so I was told) But I'm not so sure I want to be the "crash test dummy."

I've seen a couple of Webleys with blown cylinders. Both were conversions to 45acp and both let go when firing standard military surplus FMJ ammo. One was a MkIV, the other a MkVI.
A search of the British military gun websites will usually come up with a few of the same storys and some pics to go along.

That said, countless thousands of these guns have been shot with probably millions of rounds of 45acp ammo and they've held together.
Bottom line is that the service pressure of the 45acp is generally around the proof pressure of a 455 round.

Hand loaded 45acp rounds to suitable pressures would be fine IMHO, I'd personally stay away from the factory loaded stuff in a Webley.

I've owned a couple converted Webleys that had bulged cylinders. I don't know for sure if that was because fo firing 45 ACP in them but that is my suspicion. There is a reason England went with heavier cylinders for revolvers designed for nitro powder. Just because something was done as a war time expediency does not mean it should be done on a regular basis. I'd bet that the average air crew member during WW2 only fired one or two cylinders of ammo for familiarization during their entire time in a combat zone. So a converted black powder revolver would probably not cause a problem.

Thanks for the advice. I tend to agree with both of you. I guess I just wanted to hear it from someone else, to confirm my feeling.

I would like to shoot my MkI, I'll have to experiment a little. Goex loads .45 S&W in BP, and Ten X loads them in "American pioneer powder" (BP substitute) If they chamber I wouldn't worry about pressure levels. I don't reload and it wouldn't be worth the expense to get into it, for what little I shoot.

If your only looking a occasional shooting I'd look for a used Lee handloading tool. You could probably find one for <$20, which is barely a box of ammo these days. You can use 45 ACP cases with moon clips and anyone that sells cast bullets will have a suitable projectile. The dipper is all you need for BP and BP substitutes. I do not think 45 S&W will work because of rim thickness. If your revolvers cylinder was milled it needs a thicker rim.

I have 3 MK VIs converted to 0.45ACP and one Commercial still in 0,455. For the 0.45 ACP buy the Lee 0.455 dies and reload using 0.45 AR cases with a load that will give around 650 fps behind a 0,454" 255 grain 0.45 bullet. Works beautifully and mimics the 0.455 load. Dave_n