I have a set of nickel plated snap caps. I tried them in my newest toy, an N.R. Davis double. In the left tube the snap cap slipped past the extractor and jammed under it. I was able to wiggle it out with only removing the barrels. I tried an assortment of once fired hulls without problems. The snap cap must have an undersize rim.

Craig

Ask not for whom the dog barks, it barks for thee...
NRA Life Member