The rifle action I built (see DIY) is marginal on setting off primers. It sets off Winchester primers in my handloads reliably, but whatever primer came in the factory 300 AAC Blackout Barnes VOR TX ammo was only igniting maybe one in four times.

I added a knob to the back of the firing pin (just because I like the look of the cocking knob on the Springfield). It's pretty heavy. If I take it off, should the lighter firing pin assembly more reliably set off primers? Or does the extra weight help more than the speed?

I've got a pretty strong spring, and it's compressed pretty tightly comparing it to Model 70/Model 700/Mauser actions.

Thanks for the help,
Steve

Actually, it's usually the other way around. Removing the knob can sometimes result in light strikes. Stronger/heavier springs are made by Wolfe, Brownell's carries them, and they are relatively inexpensive. That's the route I'd be taking.

Actually, and I am sure an engineer type can verify, but force equals mass time velocity, so either way, the force will be the same, a lighter pin will allow the same spring to act faster, no net change in the resultant force.

So, a light pin with a stronger spring will add force. The spring adds velocity, nothing more.

Maybe more a headspace and chamber issue. Factory ammo seating slightly deeper than your reloads? Are your reloads on cases fired in that chamber, if so then they have taken up the headspace?

A shallow rounded shoulder on the Blackout case which doesn't lend itself to forgiving headspace.

It could also be a firing pin protrusion issue too. Make sure you have a .060 protrusion.

In classical mechanics, the kinetic energy of a non-rotating object of mass m traveling at a speed v is (MASS*V^2)/2.

If the firing pin moves faster the energy INCREASES by the square of the velocity delta.

I added a tungsten weight to my BR rifle's firing pin. Much better results.

You have to remember something, A spring is a fixed power device. All a light firing pin will do is get up to the max speed the spring is capable of faster. it decreases your lock time. A heavier firing pin will accelerate slower but will still reach the same speed (give or take a bit) but the heavier pin will increase impact force.

Thanks all!

quote:

Originally posted by skl1:
Thanks all!

Please let us know what you find, always good to hear results hopefully all positive for you.

Have slightly over .060 (.062) protrusion. Have rounded tip. Spring is bound up tight, and I will likely polish inside of bolt in case friction's the culprit.

The loaded ammo is 300 AAC/Blackout while the reloads were all sized by the Hornady 300 Whisper die set (although Hornady tech says they sell the same dies as 300 AAC/Blackout).

The ENERGY of a light vs. heavy pin assembly will be approximately the same. The MOMENTUM of a heavier assembly will be greater. It is momentum which makes the dent in the primer.

All things being equal, a lighter assembly will have a faster lock time than a heavier assembly. Not that that is of any benefit if the light assembly results in hang fires or no-fires.

This issue was thoroughly researched back in the days of the 1903 Springfield with the introduction of the headless cocking piece. The headless cocking piece was found to give much less reliable ignition than the "service" cocking piece and was for the most part rejected.

There might bee a "dark hores" in this diskussion. From my limited expierince i have learned that if your cartridge doesnt hav a destinkt shoulder, a lighter and faster firingpin assy, seems to Work better, Actually one could reduce springload on 9,3x62 by 20% still getting more reliable ignithion, when reducing firingpin wheight.
My theory is that slow heavy pinns require more solid stop on the caseshoulders, or the case would "absorbe" the strike, A faster strike would not allow the case to moove and absorbe the strike

Jargen,

Thanks for that idea. Since the factory cartridges were AAC/Blackout and my reloads were sized in my "300 Whisper" die, maybe there really is a difference, and they're sliding forward at the firing pin strike.