In the past, whenever I needed to dry fire a rimfire, I just gathered up some spent shell cases and used them. I did notice that after a couple or 3 firing pin hits in the same place the spent case would get work hardened where the firing pin repeatedly struck the same spot. So, occasionally, I'd rotate the empty shell occasionally to hit virgin brass.

So, with my new 317-3, I decided to try the Triple K 22 cal protective snap caps. While the centerfire Triple K snap caps have a brass button where a primer normally sits backed up by an internal spring, the 22 cal snap caps are just blow molded plastic that vaguely resemble a 22 round. The snap cap does have a rim and that, obviously, is the place the firing pin will hit.

Pros & cons: In extensive DA dry firing the 317, I noticed that the snap cap would rotate itself to a new, presumably random, area where the firing pin would hit a different area of the snap cap rim. I liked this alot, I expected to have to rotate the snap caps in their bores just as I would real spent brass. However, in extensive dry firing the entire rim of the snap cap would be riddled with firing pin strikes causing the rim to separate from the snap cap and fall out. In trying to achieve 1000 cycles dry firing, all 12 of the snap caps rims had broken off by 600 cycles causing me to revert to spent brass.

So, as long as you're not doing extensive dry firing the Triple K snap caps aren't too bad. But be aware they won't last forever. I paid $5.99 for a pack of 12 from Cabelas.

UPDATE:
I got 2 more examples of .22 cal snap caps. Both ordered from Midway. First is "Tipton Snap Cap 22 Short and Long Rifle Polymer Package of 25". These are much the same as the Triple K and Pachmayr's. They seem to be economical at $7.99 for a package of 25.

The other are "Carlson's Snap Cap 22 Short and Long Rifle Rimfire Aluminum Silver". Genuine soft aluminum. They work much like a fired case except they rotate. So the hits are randomly distributed around the rim. They are pricey though at $6.99 for a package of 6. I'm sure the aluminum ones will work harden over time and you'd have to be careful of not letting them get too hard. They can be annealed in your oven. 570 - 660F for 10 or 20 minutes. Annealing won't bring them back to "as new" but it will bring the softness back. There's another better way to anneal them with an oxy/acetylene torch. Ask I and I will reveal.

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