Chamber Checkers help you avoid jams, misfires, feeding problems, and other malfunctions caused by out-of-spec ammo. Use with factory loaded ammunition as well as reloaded ammo prior to shooting to verify your ammunition is within SPEC. These 7-Hole checkers are machined from solid 6061 T6 aircraft grade aluminum and uses actual Clymer reamers to ensure the ammo matches your chamber. Measures minimum case diameter as well as maximum overall length. Anodized Matte Black. Mfg: Egw SPEC. These 7-Hole checkers are machined from solid 6061 T6 aircraft grade aluminum and uses actual Clymer reamers to ensure the ammo matches your chamber. Measures minimum case diameter as well as maximum overall length. Anodized Matte Black.