Force Required for Primers

bpeezer · March 14, 2012, 09:40 PM

Does anyone know the force required to set off primers? I realize there are different types of primers, but I don't want to narrow the question down so much that no one has input. I searched some old threads and saw a couple from a few years ago.

http://thefiringline.com/forums/showthread.php?t=343144

http://thefiringline.com/forums/showthread.php?t=335918

The only real numbers I saw in the first thread dealt specifically with checking the striker spring. The second thread had a conjecture about 12 ft/lbs. I assume this meant ft*lbs, which is generally used for torque or energy. I also googled it and didn't see any clear answers. The question is brought on by a thread in the art of the rifle about lightweight firing pins. I was wondering if someone could shed some light on some numeric values, units, testing methods, anything that might feed my curiosity

Lost Sheep · March 14, 2012, 11:21 PM

Torque and energy are different.

I am sorry that I don't know the answer specifically, but can contribute that not only the amount of energy is important, but how quickly it is applied.

Rifle primers are made of sterner stuff than pistol primers (to contain the higher pressures found in rifles) and therefore require more energy from the firing pin to dent the metal with enough "juice" (however you want to measure it) to ignite the priming compound.

Ignition of the priming compound is because the chemicals are compressed between the anvil and the cup and compressed suddenly. It is possible to fold a live primer in half and crush it into a primer pocket without it being set off. I have done it on several occasions.

I am told that the first primers were made of fulminate of mercury mixed with ground glass or other gritty material. Nowadays they are made of Lead Styphnate, but other chemicals are being substituted for the Lead as we get more cautious about poisoning ourselves. Whatever it is, you need a Shock Sensitive Explosive for the priming compound.

I hope my contribution helps.

Lost Sheep

bpeezer · March 15, 2012, 01:03 AM

Quote:

Torque and energy are different.

I am aware of this, sorry for not clarifying. I meant that by convention, the units of feet and pounds being multiplied can refer to either torque or energy. The difference is that energy is a scalar value, and torque is a vector. From a physics standpoint, this difference is colossal. For most applications, it is sufficient to say that the scalar energy is an indication of the magnitude of the related torque.

In regards to speed of energy application, this is one of the quantities that I want to theoretically optimize. Several formulas to consider in this aspect are:

kinetic energy=1/2*mass*(Velocity^2)
Momentum=mass*Velocity
Force=mass*acceleration
Impulse=integration(Force applied) or Impulse=change in Momentum.

Long winded physics responses aside, I'm looking to calculate the weight of a firing pin that will travel the fastest (And thus have the shortest lock time) and still be capable of reliably ignite the primer. This is not for an actual application, and I don't think that I shoot well enough for this to make a difference

Interesting about crushing the primers without ignition, but when I consider their chemical nature it does seem to make sense. Thanks for your input!

mrawesome22 · March 15, 2012, 02:00 AM

The only way this might be feasible is doing lot experimentation.

The priming compounds will vary lot to lot.

Primers are very inert until you push the anvil in while seating them.

Lots of variables. Cup thickness, mixture ratios, primer pocket depth, depth anvil was pushed into compound.....

Then you would have to determine if the firing pin could make a consistent impact per pull and to the exact same spot to primers which were seated to the exact same depth woth the exact amount of anvil crush.

Maybe easier to go..... If it don't fire reliably, get a stronger spring.

bpeezer · March 15, 2012, 09:12 AM

Quote:

Primers are very inert until you push the anvil in while seating them.

That's helpful, thanks for explaining that to me. I was hoping this could all be done theoretically, but if experimentation is necessary maybe I'll have to go buy a hundred primers and do some basic testing. Of course, to do that I'd have to build the facilities...sounds like curiosity can get expensive

Japle · March 16, 2012, 04:18 PM

It’s pretty hard to get them to go off. The only way I’ve managed it in loading almost 200,000 rounds is by cramming two primers into the same pocket when an old Star progressive machine double-fed primers.

I use Federal primers for my revolver loads and seat them HARD to make sure they’ll fire in my super-tuned competition guns. Looking at the primers on my reloads, you can plainly see the imprint of the anvil.

March 14, 2012, 09:40 PM	#1
bpeezer Senior Member Join Date: October 17, 2011 Location: Ohio Posts: 118	Force Required for Primers Does anyone know the force required to set off primers? I realize there are different types of primers, but I don't want to narrow the question down so much that no one has input. I searched some old threads and saw a couple from a few years ago. http://thefiringline.com/forums/showthread.php?t=343144 http://thefiringline.com/forums/showthread.php?t=335918 The only real numbers I saw in the first thread dealt specifically with checking the striker spring. The second thread had a conjecture about 12 ft/lbs. I assume this meant ft*lbs, which is generally used for torque or energy. I also googled it and didn't see any clear answers. The question is brought on by a thread in the art of the rifle about lightweight firing pins. I was wondering if someone could shed some light on some numeric values, units, testing methods, anything that might feed my curiosity __________________ Slow is smooth, and smooth is fast

March 14, 2012, 11:21 PM	#2
Lost Sheep Senior Member Join Date: January 24, 2009 Location: Anchorage Alaska Posts: 3,341	Foot-Pounds, energy Pounds-feet Torque Torque and energy are different. I am sorry that I don't know the answer specifically, but can contribute that not only the amount of energy is important, but how quickly it is applied. Rifle primers are made of sterner stuff than pistol primers (to contain the higher pressures found in rifles) and therefore require more energy from the firing pin to dent the metal with enough "juice" (however you want to measure it) to ignite the priming compound. Ignition of the priming compound is because the chemicals are compressed between the anvil and the cup and compressed suddenly. It is possible to fold a live primer in half and crush it into a primer pocket without it being set off. I have done it on several occasions. I am told that the first primers were made of fulminate of mercury mixed with ground glass or other gritty material. Nowadays they are made of Lead Styphnate, but other chemicals are being substituted for the Lead as we get more cautious about poisoning ourselves. Whatever it is, you need a Shock Sensitive Explosive for the priming compound. I hope my contribution helps. Lost Sheep

March 15, 2012, 02:00 AM	#4
mrawesome22 Senior Member Join Date: November 9, 2005 Location: Ohio, Appalachia's foothills. Posts: 3,779	The only way this might be feasible is doing lot experimentation. The priming compounds will vary lot to lot. Primers are very inert until you push the anvil in while seating them. Lots of variables. Cup thickness, mixture ratios, primer pocket depth, depth anvil was pushed into compound..... Then you would have to determine if the firing pin could make a consistent impact per pull and to the exact same spot to primers which were seated to the exact same depth woth the exact amount of anvil crush. Maybe easier to go..... If it don't fire reliably, get a stronger spring.

March 16, 2012, 04:18 PM	#6
Japle Senior Member Join Date: October 12, 2004 Location: Viera, Florida Posts: 1,340	It’s pretty hard to get them to go off. The only way I’ve managed it in loading almost 200,000 rounds is by cramming two primers into the same pocket when an old Star progressive machine double-fed primers. I use Federal primers for my revolver loads and seat them HARD to make sure they’ll fire in my super-tuned competition guns. Looking at the primers on my reloads, you can plainly see the imprint of the anvil.