Use already fired ones. Take a punch and flatten them back out if you want. Or, some chemicals will kill a primer, but I am not sure what chemical to use exactly.
A drop of oil is what I kill one with when necessary.
I would definitely go the used one route and flatten out as already suggested. Trying to take new primers and trying to make inert with oil or whatever is just to risky. They could still go "Bang" and that might ruin the novelty real fast.Use already fired ones. Take a punch and flatten them back out if you want. Or, some chemicals will kill a primer, but I am not sure what chemical to use exactly.