Just resurrecting this thread for informational purposes. I was emailed a few questions from a few others with the same issue I was having sizing brass.
First, my original question couldn't really be answered in a manner that would be right. My fault, so thanx for the replies.
I'll try to keep this short.
It seems that the 380 Rook cartridge and the 380 Webley are slightly different. They appear to be identical but not quite.
Ganderite mentions that he uses fired 38 spl cases. Those work in the 380 Rook chamber in the rifle a friend owns, not in my pistol or apparently some other "WEBLY No2" revolvers. It appears some of them have very tight chambers.
At first glance, I thought my cylinder's chambers had shoulders machined into them. It turned out to be a build up of hard lube and powder. (embarrassing) Thankfully no pitting or etching.
My first attempt, after softening and cleaning out the fouling in the cylinders was to try 38 S&W cases, sized down in a proper die. Wouldn't fit. So tried a 9x19 die, still to big. Finally sized them down in a 380acp die and they fit very nicely, as well as being the proper length for the cast bullets my mold throws. (thanx jethunter)
Only one propblem with the 38 S&W cases I have on hand. The rims are to thick to allow the cylinder to rotate without binding.
OK, back to 38 spl cases. It's much easier to trim the 38 spl cases than it is to trim the rims of the 38 S&W. I have a nifty little holder that chucks up in my lathe. Only takes a few seconds to trim the 38 spl cases to 38 S&W length. All of the different makes of 38 spl cases I have on hand have rims that are thin enough to easily allow the cylinder to rotate. Perfect.
Just for those wondering, factory loaded 38 S&W rounds will not fit all the way into the chambers of my revolver.
So the recipe seems to be, trim 38 spl cases to 38 S&W length, size in a 380 acp die all the way to the rim, cast appropriate 125 grain, outside lubed, .380 diameter, heeled bullets, load 4.0 grains of Unique (safe) or 10 grains FFFG BP, insert the .955 diameter heel and crimp the bullet into place.
I'm going to load up both BP and smokeless tomorrow, after casting a couple of hundred bullets.
Looking forward to see how this 125 year old little revolver does out to 15 yards.