Solid aluminum caps are the way to go. These are highly visible as snap-caps and make maintenance care free. They don't have the same weight as a bullet so they will take a little work into the bore but they work as designed. 10 bucks for 2 ain't bad. Buy them for the comfort of not dry firing on your next gun.
Cons: They don't work exactly like bullets
This review was written in the old system and had content requirements that are different than reviews written today.