The legal position first. Primers are a regulated explosive. Supply requires the appropriate certificate or authority, quantity limits apply to what may be held, and they cannot simply be despatched to any address. Contact the shop to confirm availability and how a given order can be fulfilled rather than assuming it can be posted.
Sizes. Primers come in small rifle, large rifle, small pistol and large pistol, and the size is set by the case, not by preference. The range covers CCI small rifle (400), CCI large rifle (No.200 and 210), CCI 500 small pistol, Federal GM210M Gold Medal large rifle match, and RWS small rifle.
Do not substitute blind. Standard, magnum and match primers of the same nominal size are not interchangeable in a worked-up load. Brisance and cup hardness differ between makes and between grades within a make, and swapping one for another can move pressure meaningfully. If you change primer, drop the charge and work back up from current published data for that exact combination of case, powder, bullet and primer.
Handling and storage. Keep primers in their original packaging, dry, away from heat and solvents, and never decant them loose into a container. Handling them in bulk is the part of reloading that deserves the most respect.
The Hornady Lock-N-Load AP primer feed system is held here alongside the primers themselves.
Related: Powder, Brass, Bullets, Dies & Presses, Case Preparation.
