What is a "hard" primer? Quantitatively?

[patentnonsense]

Are primers specified in terms of minimum kinetic energy to fire?

Or do we have to look at some more complicated formula which specifies the elasticity of the unfired primer?

I'm thinking about a change of firing pin mass in an existing design, and want some way to assess primer strike issues.

And I'd appreciate any leads to engineering reference books on ordnance engineering, or mechanical engineering issues in weapons design.

Thanks very much!

 

[Texasbagman]

In my experience, primer cup hardness has more to do with who made it than any specific engineering spec.

I've always found Federal primers require the lest amount of force to ignite. And CCI to be the hardest.

But I have met reloaders that don't agree.

I've been reloading for a long time, better than 20 years, and the only brand of primer I've had mis-fire was CCI.

 

[goldust]

I've got no scientific evidence to offer on the subject but I can agree with Texasbagman about CCI primers. In the past 25 years I've loaded thousands of rounds. Occassionally I'd get a failure to ignite double action on some revolvers, usually CCI primers. That's when I would replace the mainspring.

But you asked for quantitative information. Sorry I don't have any. Are primer cups chrome plated? Could the plating have anything to do with this "hardness"?...minor production run variances in cup thickness, maybe.

 

[Cosmoline]

Conversely, I've found CCI primers perform the best for hard-hitting Mauser and Mosin reloads. The old military rifles often prefer deep-seated primers as well and I'd never press hard on a Federal!

 

[JeremyIA]

Most cases I've examined were not cases of "hard primers" but "not-fully-seated" primers. The kinetic energy of the firing pin was expended by fully seating the primer but not enough energy remained to touch the primer off. That's why I like double-action guns. In a defensive situation I would prefer to be able to give the trigger a quick second squeeze if the round doesn't fire the first time.

In the case of a primer defect, it's always been a not-fully-seated primer in my experiences on the range. A second squeeze of the trigger has ALWAYS touched the round off. The primers just weren't fully seated to begin with. Primer hardness had nothing to do with it.

 

[Jerry the Geek]

I suspect you're not going to get a "quantitive" answer on this forum. If you want numbers, you would be better off addressing your inquiries to manufacturer or, possibly (but not likely) reloading manuals.

You MAY get anecdotal evidence from this forum, and you can give it as much credence as it deserves. Here is my anecdotal commentary:

Shooters are often pragmatic, in that they (for example) use mainsprings to determine the amount of kinetic energy needed to ignite their primer of choice. The choice is dependent, usually, on the application and the amount of internal pressure endemic to the load.

For example, I shoot IPSC in both Limited and Open Divisions. My Limited guns use ammunition (9x19, .45ACP, 10mm) which is loaded to develop relatively low internal pressures. For those, I use Pistol Primers (eg: WSP). However, in my .38 Super, I expect high pressures. Therefore, I use primers which are 'harder' and are more likely to withstand these pressures. Rifle primers are designed with 'harder' metal in the cups, so I use rifle primers (eg: WSR).

You have received comments referring to CCI Primers. They are notably 'soft' primers, and revolver shooters use the softest primers they can find in order to minimize the amount of energy impated to the primer by the hammer. Why? Because every ounce of energy imparted to the hammer must be delivered by the trigger-finger, and in double-action pistols their goal is to minimize trigger-pull, in order to improve accuracy.

In ALL actions other than double-action, the energy deliverd to the hammer (or fining pin) is augmented by the action of the slide/bolt (semi-automatic, fully automatic) in response to the detonation of the previous round,or or other cocking mechanism (the thumb in single-action revolvers, for example, or the bolt or lever or pump, etc. in other actions.) People using these actions don't CARE how much energy is necessary to impart to the firing pin/hammer, except in highly competive situations where the amount of time needed for the firing pin travel to complete its action is significant.

Ultimately, for most people the choice of primer is determined by its ability to withstand the internal pressures generated by the load in that firearm. Other variables, such as the amount of energy which is required to ignite the primer, can be compensated for by selecting the firing pin spring weight, or the weight of the firing pin itself (often determined by the material from which the firing pin is constructed, as in "steel" vs "titanium".)

The bottom line, if you will, is that if you want to change the firing pin MASS, you can insure consistent ignition by changing either the primer, or the momentum (perhaps not 'kinetic energy') of the firing pin SPEED. This latter can be influenced by increasing either the firing pin spring, or perhaps the hammer mass or speed (whichever is appropriate to your design change.)

In other words; be pragmatic. Establish the constants of your design, then fiddle with the variables until you get a combination that works.

Jerry the ("WORKS" means, the gun fires every time, and the primer doesn't blow out!) Geek