Height in Millimeters Which 100% of Primers Must Fire

[John Boy]

How many times there have their been posts "I put an aftermarket main spring in my firearm and I am having light primer hits" The replies usually are " Use Federal primers, they are the softest" - which is the wrong answer - it's the force of the main spring needed to crush the anvils that ignite the primer for any type

 

So, how much main spring pressure is needed to ignite a given primer? This is the test that the manufacturers use with a Primer Drop Test Fixture with a 1.94 or 3.94 ounce steel ball based on years of experience. Summarized, the mm of force are:

 

Rimmed Case: 325mm SR - 255mm SP - 275mm LR - 250mm LP

Rimless Case: 335mm SR - 205mm SP - 305mm LR - 290mm LP

The higher number needed for rimless cases are due to the cushioning effect of the cartridge shoulder

Source: 3rd Edition Ammo Encyclopedia by Michael Bussard

 

So, if one is a 'kitchen table gunsmith' or one buys after market springs ... Determine the millimeters you or the vendor calculated for a specific type of primer for rimmed or rimless cases... Irregardless of Primer Brand!

 

 

[Springfield Slim SASS #24733]

And what exactly is the formula to relate this to the pressure at my hammer? Does this allow variances for dirt, caliber, headspace clearance, hammer and firing pin weight?

[H. K. Uriah, SASS #74619]

Rimmed Case: 325mm SR - 255mm SP - 275mm LR - 250mm LP

Rimless Case: 335mm SR - 205mm SP - 305mm LR - 290mm LP

Or if you prefer..

Rimmed Case: 12.7953" SR - 10.0394" SP - 10.8268" LR - 9.84252" LP

Rimless Case: 13.189" SR - 8.07087" SP - 12.0079" LR - 11.4173" LP

I don't do metric.

[Gold Canyon Kid #43974]

Using Federal primers is a lot easier. I think folks are smart enough to pick and set their primer springs. If they are not, then maybe rheir gunsmiths are. I know one shooter that won EOT with a hammer spring so weak it was hard to keep the hammer down at the loading table. Later he was convienced he was getting slower hammer fall times and moved to stiffer hammer springs.

[Nate Kiowa Jones #6765]

The factors you didn't cover is headspace and firing pin protrusion. All those weights are meaning less if the headspace and firing pin protursion aren't correct. You can't assume the out of the box gun is correct. For our pistol cal guns the gold standard should be Colt SAA spec or .045 to .055".

But, I have never seen a Ruger or Uberti with that much protrusion. They seem to depend on inertia of the firing pin going forward. That sets up some variables so just changing to lighter spring will make for an unreliable gun, and to me, an unreliable gun is a gun that will only pop federal primers.

 

Protrusion, headspace then look at changing springs.

[Warden Callaway]

I've had problems with primers that were not seated to bottom of primer pocket.

[Cat Brules]

Why pick apart John Boy's explanation?

 

OBVIOUSLY no such treatise of explanation will make allowances or references for subjective, uncontrolled conditions such as poor weapons maintenance, worn out or faulty weapons, weak aftermarket springs, etc., other than to disallow them.

 

Commercial primers, as components for reloading, are pretty much alike, empirical evidence aside. I use Federal primers, too and I don't for a moment discount JB's diagrammed explanation of the testing of primers. There are any number of us here that will not engage in this discussion, who use "off-brand" primers and who never experience failures.

[Garrison Joe, SASS #60708]

Commercial primers, as components for reloading, are pretty much alike, empirical evidence aside.

 

Empirical evidence (practical experience) really cannot be ignored on this topic. There is WAY too much experience that shows that it is easier to ignite the Federal line than all the others. Arguing over any one person's definition of "hardness" or "softness" is just silly, IMHO.

 

There ain't nothing that works, like a primer that works.

 

But it is Interesting to see the rig that at least one factory uses. Now if we just knew what drop distance values each of the primers made commercially are "reliably firing" at, we'd start to really know something.....

 

Good luck, GJ

[Yusta B.]

I wanna know how many millimeters in a 14# spring ????????

[Garrison Joe, SASS #60708]

I wanna know how many millimeters in a 14# spring ????????

7.62 millimeters. Oh, no, wait, that's groove diameter on an M-14.

[Yusta B.]

7.62 millimeters. Oh, no, wait, that's groove diameter on an M-14.

Ok - so maybe a 1.94 oz steel ball mounted on my hammer ??????

[Assassin]

Ok - so maybe a 1.94 oz steel ball mounted on my hammer ??????

1.94 inches is the size if an intake valve on a 300hp 327 cubic inch Chevy.

[Yusta B.]

:P :P

[Buffalo Bill Mathewson, 37826]

John Boy, Thanks for OP

[Carolina Gunslinger]

Interesting information. I'm sure we could calculate the force generated by the ball over the distance traveled using the formulae that we learned in physics. I'm just not sure how to translate that into something I can measure at the gun's action.

 

After years of fiddling around with double action revolvers I have come up with a simple method. Put your finger over the firing pin hole on the recoil shield in an empty, unloaded revolver. Pull the trigger. The firing pin should hit the firmly pressed finger(nailbed should not be white at the tip of the fingernail) with sufficient force to sting with a little bit of a after burn to it. That is my field expedient method to see if the gun will work 100% at a match or not. Some folks like to see an unsharpened pencil shot out of the barrel a certain distance. For the lever action rifle, I like to hear a loud positive click for a hammer fall and maintain the fastest lock time possible. A fellow shooter whom I admire brought up the lock time point during a post match discussion and it really made sense to me that a faster action versus the extra softness given by a lighter hammer is more desirable. For the 97 backing off the hammer strain screw to about flush with the top of the elevator block and then aligning the screw notch fore and aft or side to side depending on OCD preferences using blue loctite seems to yield a smoother cycle and still sets off all bargain brand shells.

 

I agree that the gun which sets off only Federal primers is not a reliable gun. There is no way out if you have a ammo picky gun and something happens to your ammo supply or primer supply.

Firing pin protrusion is also a key area to pay attention. NEF shotguns are not the best at setting off Federal shells due to the short firing pin or the deeper set of the primer. I missed a deer two feet from the muzzle that way once.

[John Boy]

But it is Interesting to see the rig that at least one factory uses. Now if we just knew what drop distance values each of the primers made commercially are "reliably firing" at, we'd start to really know something.....

Joe, I've asked them all this question except S&B. Believe we would have a better chance winning the Mega Millions than for the vendors to divulge this information

 

I wanna know how many millimeters in a 14# spring ????????

Yusta, read Carolina's post

 

Carolina, BTW ... enjoyed reading your post! FWIW, I use a trigger pull gauge to measure in ounces how much force hammer generates. Picked this up when I was putting light springs in my '58 NMA cap & balls

[Carolina Gunslinger]

Carolina, BTW ... enjoyed reading your post! FWIW, I use a trigger pull gauge to measure in ounces how much force hammer generates. Picked this up when I was putting light springs in my '58 NMA cap & balls

Hey John Boy,

I don't own a trigger pull gauge at this time. I have never really worried about the exact weight. I worried about sight disruption in target rifles and smoothness everywhere else. If I recall correctly, you need 3.75# of hammer force to be duty reliable on a S&W revolver. However, if it nips my finger and burns afterward, it will keep going bang with CCI or Federal primers. I also use set screws to set the strain on the Smiths measuring the distance between the frame and spring along the center of the set screw with the hammer at rest. That's only when I am chasing Federal only action weight and I no longer crave that.

Pray tell just how light can one set those hammers and still have them pop caps 100%? Is it a lighter action than a center fire? I'm devoid of knowledge here and you have picqued my interest indeed.

Best,

CG

[Griff]

Gosh, I'm sure glad I don't have these problems... John Boy & Carolina Gunslinger, thanks for your explanations. not sure this ol' country boy understands 'em, but interesting, regardless!

[Carolina Gunslinger]

My Vaquero solution involves calling a fella named Long Hunter, buying his springs and putting them in. I haven't had any problems beyond that with any ammunition or primers. Not everything is complex.

[CodyMaverick]

Certainly are some interesting comments here. But I think I'm missing the practical value.

 

The data in the OP is given for rimmed and rimless cases but the test jig shown is using some kind of primer holder. Unless you change the setup to hold actual primed cases in the same manner they would be held in the chamber and tightly control the seating depth of each test case, I don't see how anyone would get from the test stand to the data listed.

 

The data listed doesn't include the specific brand and type of primer it is for, nor does it give the values for the various primers available for comparison purposes.

 

The math is missing that shows how you would translate the mm in to an actual unit of force.

 

Using a trigger pull gauge on the hammer might be of practical use in comparing the relative differences in a variety of hammer springs but the actual readings would not be very accurate since the spring in the gauge will be absorbing some of the energy and skewing the results. I have used mine to compare the amount of force required to cock the hammers with different springs installed and found that there is only a proportional relationship between the # rating of the spring and the reading on the gauge. e.g. a 14lb spring in my Rugers takes about 3.5lb to pull the hammer back to full cock, IIRC.

 

Measuring firing pin protrusion is valid with a gun where the firing pin is attached to the hammer but in my Rugers the firing pin is capable of protruding far enough to puncture the primer if the hammer were to drive it that hard. Whether the hammer will deliver enough energy to cause the pin to fire a particular primer has a few more variables to consider.

 

I rather like CGs finger tip method and it certainly would seem likely that if the firing pin will sting your fingertip then it would also set off a primer.

 

Personally; I test my guns to make sure they will fire Winchesters reliably and then use Federals. For my '73s I make sure the hammer drops fast and stays put with no bounce, not very scientific but works for me.

[Noz]

17# hammer springs will fire a #10 Remington cap every time. 15# hammer springs will not.

[J-BAR #18287]

17# hammer springs will fire a #10 Remington cap every time. 15# hammer springs will not.

 

 

Yep.

 

Anyone want to buy a bunch of Ruger/Blackhawk 15# Wolff springs?

[Carolina Gunslinger]

Firing pin protrusion is valid data if you can get it. One of my Rugers had an out of spec hammer. I had always noticed the difference in protrusion between the guns(NMV). When I swapped out the hammers I forgot about it up until I tried to use the original hammers again in a set of OMV. That was a big no go and I found the cause of the protrusion difference.

 

However fire or doesn't fire is the most important part.

 

 

Thanks for the info in the cap guns!

[John Boy]

The data in the OP is given for rimmed and rimless cases but the test jig shown is using some kind of primer holder. Unless you change the setup to hold actual primed cases in the same manner they would be held in the chamber and tightly control the seating depth of each test case, I don't see how anyone would get from the test stand to the data listed.

Cody, if you have a more precise way for primer testing done by the manufacturers - devise it, patent it and send it to them.

Their testing this way seems to be doing OK for the millions of commercial & military primers produced annually

[Michigan Slim]

1.94 inches is the size if an intake valve on a 300hp 327 cubic inch Chevy.

I made mine 2.02 so it would reliably fire CCI Fuel.....

[CodyMaverick]

Cody, if you have a more precise way for primer testing done by the manufacturers - devise it, patent it and send it to them.

Their testing this way seems to be doing OK for the millions of commercial & military primers produced annually

 

Once again I think I have mis-communicated. I'm just not getting how the OP could be used to help us amateur gunsmiths (i.e. tinkerers) in selecting mainsprings or troubleshooting light primer strike issues.

[Three Gun Cole]

My guns are set to be able to fire CCI primers,

And I only use Federal gold match magnum primers, Zero mis-fires, if the hammer falls, the gun fires.

 

 

3GC

[Cowboy Rick, SASS #49739L]

 

Once again I think I have mis-communicated. I'm just not getting how the OP could be used to help us amateur gunsmiths (i.e. tinkerers) in selecting mainsprings or troubleshooting light primer strike issues.

I think JBs post can help anybody understand that there are minimum ignition standards for each type of primer under varying conditions. A small pistol primer that will fire reliably in a rimless case may not do as well in a rimmed case due to the increased force required to ignite the priming compound. This type of information can help with an overall understanding of how to set up the guns you're shooting. If you wish to be at the mercy of a specific brand, you know ahead of time that you've limited your supply line.

 

CR

[Carolina Gunslinger]

John Boy's post was neat and informative, a sort of a this is how they do it.

 

Cody Maverick's post is a curiosity of how to turn that data into something the shooter can use.

 

Realistically what can the shooter do with the information that a two ounce ball falling from x distance pops the primer? Not much as it is not readily transferrable into data that can be measured by the shooter on the action of the firearm.

 

A third and final aspect of rimmed vs. rimless debate has been over looked: moonclips. The spring steel provides a little bit of give to the primer when struck. This is evident when a bullet is pulled kinetically out into the cylinder throat on a reduced strain action, often times the primer will not ignite. In this case there are no case mouths setting headspace. I have no way to empirically quantify the difference between the semiautomatic pistol and the moonclip revolver except by the required hammer strain in pounds to set off the cases.

 

It seems like all that time I spend calculating this information is moot except to determine which primers are softer. Couldn't I just do that in an afternoon with a trigger pull gauge measuring hammer strain? Then and there would I have data that other shooters could use in real time. The more I read into this discussion, the more I am convinced that this issue is best tackled with real world data gathered on a specific platform and passed along for the end user to refine to their individual guns. Much like...external ballistics and zero...😎

[Cowboy Rick, SASS #49739L]

John Boy's post was neat and informative, a sort of a this is how they do it.

 

 

Also to demonstrate that there is a standard and uniformity to the process. It is not a random process, so when you do get the hipshot spring tension just right - it will work all the time. To me, there is some peace in knowing.

[CodyMaverick]

Also to demonstrate that there is a standard and uniformity to the process. It is not a random process, so when you do get the hipshot spring tension just right - it will work all the time. To me, there is some peace in knowing.

 

Pretty much any mass manufacturer of anything will have a QC dept. that initially and then regularly checks the product to be sure it meets whatever design criteria they have. Just like you do when your reloading. I'm sure you pull samples regularly and check them to be sure everything is coming out right. But; even with all that, defects still manage to slip through. The best you can hope for is they are few and far between.

 

So; Be at peace.

[CodyMaverick]

John Boy's post was neat and informative, a sort of a this is how they do it.

 

Cody Maverick's post is a curiosity of how to turn that data into something the shooter can use.

 

Realistically what can the shooter do with the information that a two ounce ball falling from x distance pops the primer? Not much as it is not readily transferrable into data that can be measured by the shooter on the action of the firearm.

 

A third and final aspect of rimmed vs. rimless debate has been over looked: moonclips. The spring steel provides a little bit of give to the primer when struck. This is evident when a bullet is pulled kinetically out into the cylinder throat on a reduced strain action, often times the primer will not ignite. In this case there are no case mouths setting headspace. I have no way to empirically quantify the difference between the semiautomatic pistol and the moonclip revolver except by the required hammer strain in pounds to set off the cases.

 

It seems like all that time I spend calculating this information is moot except to determine which primers are softer. Couldn't I just do that in an afternoon with a trigger pull gauge measuring hammer strain? Then and there would I have data that other shooters could use in real time. The more I read into this discussion, the more I am convinced that this issue is best tackled with real world data gathered on a specific platform and passed along for the end user to refine to their individual guns. Much like...external ballistics and zero...

 

 

Right and all that 'data' will do is get you to the neighborhood. You'll still have to walk around on your own to find the address you're looking for.