Manufactured to exact specifications, including diameter and length dimensions, weight and balance of factory loaded ammo, these DUMMIES have the proper functioning characteristics to reliably check magazine feeding, action timing, extraction and ejection of all guns. The only professionally accepted and safe way to check gun functioning; live ammo should never be used except in actual test-firing on the range - after you have checked the gun with DUMMIES. The very reasonable cost per DUMMY is an added incentive to use them regularly. The blackened case makes them distinct, and instantly recognizable as DUMMIES, which makes them ideal - and safe - to use as a sales aid. Especially useful when demonstrating how a particular gun functions or in gun safety instruction classes. They absolutely eliminate the chance of an accidental discharge. The .17 Mach 2 and .17 HMR dummies are not recommended for tubular magazines.