CCI Mini-Mag .22 LR 40 Grain CPRN: Rimfire Headspace Sensitivity and Ignition Reliability Rimfire cartridges rely on precise headspace alignment to ensure proper primer ignition. Variations in headspace tolerance can affect firing reliability. CCI Mini-Mag .22 LR 40 Grain CPRN is manufactured with consistent dimensional control that supports reliable headspace engagement across ... https://bulkammotogo.com/product/22-lr-40-gr-cprn-cci-mini-mag-0030-5000-rounds/