Since I have been cited here some clarification is in order regarding my Centaure conversions.
Karl Nedbal did a couple for me, namely Thuer, Richards, Richards Transitional, Richards-Mason, "Mystery". Klaus Mumme did three Long Cylinder Conversions for me.
Nedbal Centaure conversions: all of the breech loaders are .44 Colt cal. for inside lubed for .429 dia bullets, all have newly lathed cylinders.
Currently I am using the 8" barreled Centaure Richards as my back-up gun in CAS activities. Had to use her once only.
Only for the Thuer conversion Nedbal used the original percussion cylinder.
We planned on converting one Centaure to a Richards Transitional in .44 Colt outside lubed bullets (!). For this project the percussion cylinder was planned to be used. Nedbal felt there would be enough metal in the rebate area to be safe ... but he was concerned regarding the cylinder notches which the Belgians cut too deep on the percussion pistols. If we would have proceeded with that project he would have welded the original notches shut and recut them to less depth. We eventually agreed to do this R2 project like the others for the inside lubed ammo with a newly lathed cylinder.
Mumme Centaure Long Cylinder conversions: they are again for the .44 Colt inside lubed cartridges. They have newly lathed cylinders. They are my main match pistols for more than 2 years now.
I rarely shoot BP loaded cartridges through my conversions, > 95 % smokeless ammo with 200 grainers. All my .44 CAS match loads exceed factor 112,5 in the 5,5" barreled Centaure Long Cylinder conversions. Cases used are mostly from Black Hills factory ammo and some Starline, too.
Hope that helps
Long Johns Wolf