Load the round as normal, leaving out powder and the spent primer. Then take a trip to the hardware store, go to the plumbing section. Look for replacement o-rings for larger valves. They are usually in the little drawers near the faucet repair supplies. Find an o-ring that when cut in two has a diameter that pretty much fills the primer pocket. Cut the o-ring about an 1/8th of an inch longer than the primer pocket, fill the primer pocket with super glue gel (after cleaning it well), insert the piece of o-ring, wait for it to dry, then use a razor blade to trim it off flush with the case. The o-ring piece will stand up to thousands of snaps and is easy to replace even if it does wear out. I've never had one fail. It's also a good idea to mark the round as a dummy somehow or other.