Some ten years back or so a friend and I were checking out a gun shop a ways from our normal habitation and found ten tins of CCI #10's at what was a good price. We split the ten, five each. I for the most part have always used Rem 10's, on occasion CCI #11's. Trying the CCI #10's on my stable of Uberti Colt cap guns and several Pietta's I found that none of them fit on the stock nipples. One exception, sometime back I bought a Pietta 58 Remington from a guy on another forum that came with two cylinders. Another guy on the same forum had a 58 Remington Pietta cylinder for sale so I bought that. I found that one of the cylinders for that Remington would kinda accept the CCI 10's.
All of the nipples on my other cap guns would allow the CCI 10's to fit maybe a 1/16" or so on and you'd have to really push the cap in an attempt to seat it. I didn't have the courage to try it with my fingers, used a wooden dowel, but never did fully seat one. The one Pietta 58 Remington cylinder that did 'kinda' accept them still needed some dowel persuasion to try and get it fully seated. Never did use them, still have em, figured they were to much of a PITB to deal with not to mention hazardous trying to seat on a loaded chamber. Just tried em for fit on empty chambers.
A few years ago I bought some replacement nipples for some of my capguns. Bought some Slix, Track of the Wolf (similar to Treso's), had a spare cylinder for a 51 Pietta Navy 44 that I bought that came with Treso's, and another set of Treso's. I tried for fit CCI #11's, Remington #10's, RWS 1075's, and the **CCI #10's**. All of the first three caps I mentioned had no problem with any of the replacement nipples for fit (and on the factory stock nipples), although Rem 10's are still my favorite and best IMO to use. NONE of the Slix, Track-Wolf, or Treso's wanted anything to do with the CCI #10's just as any of the factory nipples on any Uberti or Pietta revolvers. Just what I experienced with the assortment of 10 Uberti/Pietta revolvers/models I have on hand. They have some use somewhere, possibly on some of the smaller less than 36 caliber revolvers or single shots (just a guess). For now they're just taking up space in the bottom of the container I store percussion caps in.
FatherJohn---If you haven't already seen it, go to the 'Darkside' section, click on 'The Dark Arts', about 2/3 down the page there is an excellent and informative article posted by Mako (who use to post on CAS) titled "Cap Gun Primer". Very well written with pictures. It was written back when Treso's were the rage, before Slix's came around, but just as informative. CC