Is it a pipe dream to think I can find an unshaved cylinder for a Webley?

How expensive is it to have a new revolver cylinder made, anyway?

They do pop up from time to time, but they are not common.

I had one in 45 ACP. I shot is some and never had a problem.

If I still had it, I would reload it and download the 45 to 455 level pressures. I can easily be done with 185 grain SWC, Plus those make really nice clean round holes

I searched in vain for an unshaved MK VI cylinder for years.
I eventually had a gunsmith make a piece and silver solder it to the rear of the cylinder.
Hard to see and now shoots .455.

I have one of each, and I'd love to find another unshaved cylinder.  The alternative is to load the 45 ACP down to cowboy load levels, and use a 255gr. lead semi wadcutter normally loaded in 45 Colt.

Shooting standard pressure 45 ACP in a shaved cylinder Webley is flirting with disaster, as .45 ACP is very close to the proof load for .455 Webley.  Lots of Mk. VIs have been blown up shooting a steady diet of standard 45 ACP.  Just because you have gotten away with it so far isn't proof that it's safe, it's just proof that you have been damned lucky.

Do they blow up or does the locking piece just stretch to the point where it won't lock up?

I have seen photos, and talked to folks that have had both failure modes.  Stretched and or cracked latch toggles, and blown up cylinders.

With the scarcity/value of these pieces now I don't understand even taking a chance on shooting standard 45ACP in one.

Scarcity?  There's one in my LGS chambered for .45 ACP.  A half-million were made, and thousands were converted b/c .455 Rimmed was a scarce cartridge here.  With the mindset from the black powder era of if it fits, it shoots, they seemingly worked fine for many years.  In the pre-internet era I never heard of any problems and a Mk 6 in .45 ACP was on my wish list.

There are more pics on the interwebz of blown up Ruger revolvers than Webleys - likely b/c modern revolvers are shot far more than their predecessors.

Current production is in .357 Mag, so there's no inherent weakness in the design - it's a question of metallurgy of the day and the original specs.

They turn up on Gunbroker from time to time but not often.   Expect the price to be well into four figures.

I hope this isn't much of a derailment.
I have a MK VI that I'm pretty sure is shaved.
I've been searching around but I can't find the length of an unshaved cylinder vs a shaved one.
Does anyone know or can share a link?

Easiest way to determine if it was shaved is to look at the rear face of the cylinder. If there are factory markings present, it's unshaven. No markings and most often in the white, then shaved. Also, if the serial number at the back of the cylinder is missing the bottom of the numbers, it's shaved.