CCI #400 Small Rifle Primers, 1000 ct

The CCI #400 is the standard small rifle primer, and it covers more cartridges than it used to. Beyond .223 Remington, a growing share of .308 Winchester and 6.5 Creedmoor brass now ships with small rifle primer pockets, so check the case rather than the cartridge name before you buy a thousand of the wrong size. As with the #200, CCI publishes marketing copy rather than specifications for its standard primers and states no cup thickness, hardness, or sensitivity figures, so the numbers circulating in forums are not manufacturer data. One selection point does deserve care. For 5.56 loaded into a military-pattern semi-automatic, CCI builds and designates a separate primer, the Mil-Spec No. 41, describing it as built to military specification and specifically designed for use in 5.56 cartridges; the No. 34 fills the same role in large rifle for 7.62. CCI does not publish a prohibition on using standard primers in semi-automatics, but where the maker has designated a primer for that application, that designation is the reason to prefer it in a rifle with a free-floating firing pin.