Get one of the straight "stick" cappers, that will fit any percussion gun. they are very cheap, and they will work. The worst thing that happens with any capper is sometimes the caps turn on their sides, and you have to fish them out with a knife, or pin. I learned to just use my thumbnail to pull open the little spring to let the cap fall out into my hand, when they turn on their sides. Then I put the cap on the nipple manually, AND carefully!
I use the Ted Cash oval capper, because it holds an entire tin of 100 caps, and I can get it around the rifle and shotgun nipples I fire. I don't shoot revolvers anymore, but it used to work on my Navy .36 revolver, when I did. I know it will work on the Ruger old Army, too. I can't say anything about the Paterson revolver, because I have never shot one. Some of those Italian replicas call for using #10 caps, rather than the more common #11 caps. Be sure you get caps that fit those nipples. The smaller caps are more likely to turn sideways in the capper, regardless of what type or brand you use. :hmm: :thumbsup: