Priming is something that can be done on- or off-press. On-press priming is done with a little priming arm that fits one most presses. This arm is easy to add and remove from the press. Typically it simply drops into a slot in the ram and pivots the primer-holding cup up under the brass case through the shell holder when the ram is lowered.
This is a picture of the two priming arms that come with most presses as standard equipment. While there are large, small, and magnum small pistol, large pistol, small rifle, and large rifle primers, there are only two sizes of priming arm – large and small. All the large primers (pistol and rifle) fit in the large priming arm and all the small primers (pistol and rifle) fit in the small priming arm.
Primers can be placed in this cup one at a time and when the ram is lowered over this arm on the downstroke the primer is inserted into the case. When the shell holder with cartridge are lowered, the arm is pivoted by contact with the body of the press. The cup with the primer is swung into position directly under the hole through the shell holder. As the ram bottoms out, the primer is forced into the primer pocket in the case. This is not a task that takes a lot of force. The primers go easily into the primer pocket, especially with all the leverage of the arm and ram on the press! A steady, even pressure is all that’s needed. This is a picture of a small pistol primer in a primer pocket ready to be inserted in a 38 Special case. The only thing(s) you can screw up here are 1) too much/too little force (a little practice goes a long way!) 2) putting the primer in upside down, or 3) putting the primer in the cup on the priming arm sideways. (Yes, this last one can be done. See the picture of the one I put in sideways under “Mistakes.” In the unlikely event a primer is discharged during the seating process with this tool in the press, the blast will be aimed through the open case in a directly vertical direction, not towards the operator.
Priming can also be one off-press with hand priming tools. Here’s a picture of an RCBS hand priming tool (my favorite go-to primer). I have the entire tool in a fairly vertical position so that you can see the priming tray with primers in it and the little “gate” that allows only one primer at a time down the “chute” into the priming area. When I am actually squeezing the handle to insert a primer in a case, the entire tool is tipped so that the open case is pointing away from my face. In the unlikely event that a primer discharges during the insertion, the blast from the primer is aimed through the brass case away from your face.
No matter what your choice of tools for the priming process, primers are properly inserted when they are .003″-.005″ inside the surface of the bottom of the case. This distance can be measured with a caliper. You can also develop a “feel” for the correct depth when you slide your finger tip across the bottom of a freshly primed case. It really does feel slightly recessed.
Primers not seated deeply enough are dangerous. They can be accidentally ignited by any substantial force on the bottom of the case, not the least of which could be a “slam fire” when the case is cycled into a chamber.
Primers seated too deeply are equally troublesome, but not as dangerous. The risk typically isn’t of unanticipated ignition but the opposite – the striker or firing pin not being able to make sufficient contact to ignite the primer. This can also be dangerous, however, because sight contact could create a “hang-fire” or delayed ignition. If someone pulls a trigger and there is not immediate ignition, the cartridge could be cycled out of the firearm prematurely and/or the gun pointed in an unsafe direction only to experience a delayed firing with obviously dangerous results.
Some rules of thumb:
- Never have out more than one size and manufacture of primer at a time.
- Never have out more than you need (one card of 100 maximum)
- NEVER, NEVER, NEVER try to adjust the seating depth of a primer once the case has been fully assembled! (See pictures of possible consequences under RELOADING/MISTAKES.)
- Always wear eye protection when reloading, especially during priming and powder charging steps, including using hand primers.
- Always point the case away from your face when actually inserting a primer using a hand primer.
See some hand primers under “Equipment Reviews.”
Joel Guerin, Versailles, Kentucky
For an article on substituting primers, click here.