Ideal for releasing mainspring tension when storing shotguns These precision shotgun snap caps are similar in weight to standard ammunition, ideal for realistic function testing. These are especially useful for releasing the tension on the mainspring for long-term storage of your shotgun. Cowboy shooters use shotshell snap caps for loading and dry fire practice. Whether you need snap caps or training rounds for a side-by-side or over/under shotgun (U/O), shop Lyman today!