For all of you saying that snap caps are unnecessary in modern centerfire guns...
There are many examples of broken breech faces on Glocks from dry firing without snap caps.
There are many examples of broken striker retaining roll pins on XD/XDM pistols from dry firing without snap caps.
I've ready similar reports of broken firing pins on other guns from dry firing.
I'm sure there are others, but those two come immediately to mind. I'm certainly in the camp of, "It's cheap insurance." I especially like that thay are a unique color as well. It's much better training.
If you're making a dummy round with a spend casing and you train yourself to check the breech, see brass, and it's okay to pull the trigger... that seems like a recipe for disaster. I hope you're painting the casings of your dummy rounds something unique.
Stay safe.