If you're using a modern centerfire gun, you don't need snap caps. Same goes modern for rimfire guns. Only old .22s and certain unusual guns are a problem.
I have a Wichita Silhouette pistol and a couple of old .22 rifles that can't be dryfired. All my 1911s, CZs, BHPs, wheelguns and rifles have been extensivly dryfired for decades.
Most of the snap caps I've looked at say on the package that they're not to be used as snap caps. You can use them for training, but not as snap caps.