Firing Pin effect on ignition

ab_bentley

ab_bentley

New member
Recently on 6mmBR.com I posted a 40x that I salvaged by taking a long action bolt and fitting it to the action. Then modifying the bolt body to take savage heads. In the thread I mentioned that the firing pin only have .125" of travel and .032" protrusion, I got a few responses that has made me curious. Most of the responses mentioned that the short lock time, even with constant ignition, wouldn't necessarily create uniform ignition, which would result in fliers. Even with the short pin fall, I have shot several small groups including one right at an inch at 400yds. I got so curious I made another firing pin for the rifle, with .200" pin travel and .052" protrusion to see if it made any difference.

I guess I am asking what does the consensus here say about pin fall and protrusion? Do primer ignite in a uniform manner regardless the pin fall and protrusion?

** I can see excessive headspace playing a large role in this, but my cases are bumped back .002", not really allowing my case to run from the pin.
 
At a gun nut lunch meeting last Friday there was some discussion about firing pin travel and spring force. The firing pin spring can also be a factor in consistent ignition.
 
Why would it? It is within the range considered normal. BTW I believe the usual consensus is that the primer stops the pin, not the pin shoulder, so protrusion should have nothing to do with piercing primers.
 
Boyd Allen said:
Why would it? It is within the range considered normal. BTW I believe the usual consensus is that the primer stops the pin, not the pin shoulder, so protrusion should have nothing to do with piercing primers.
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Interesting.... so... for the sake of discussion... a pin protrusion of 1/8" would be o.k.....................?????........in theory....????
 
all of my guns are setup with protrusion of 50 to 60 thou. and FP fall somewhere in the .200 range.

20-22lbs measured spring force.

i'm sure you'll get replies from guys far more successful than myself, but i'd be willing to bet that this is the generally accepted norm.
 
Fwiw. ..I fought an accuracy issue for a whil, a few years back on a custom. Replaced spring, shot like a new barrel.
 
If you extend the tip of the firing pin and keep everything else the same, you decrease the firing pin fall, which may or may not be a problem, depending on what you started with, and how much you extend the tip. If you fire a primer, and measure the depth of the dent in the primer, from the case head (It would be best to use a tight fired case to do this.), you are very likely to come up with a number that is less than the protrusion of the pin from the bolt face...by a significant amount. Unlike most other actions, Savages have adjustable pin protrusion. Bob Greenleaf, retired from Savage where he worked as an engineer for many years, wrote that he set his at .035, well under what is considered "normal".
 
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On this pin I shortened the OAL and the collar, this pin is fluted and i used a new spring. It'll be interesting to see the differance.

Adam
 
This is based solely on anecdotal evidence from my own experience. I think that in actions that have a firing pin similar to a Remington's, anything less than .200 travel is a detriment.

I also think you need a minimum 20 lbs of static spring tension. All of my Benchrest Rifles are at about 23 lbs.


Protrusion? .045 seems about optimal.
 
B.Larson said:
didn't the pin with .052" protrusion pierce primers...???
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Can someone just tell this man that firing pins aren't "pierced"......EVER???

They're "blanked,"

you can't "pierce" a primer cup with a firing pin.

Even with 1/8" of fall.

Turds in the catbox is one thing but this is just WRONG and takes from a good discussion.
 
firing pins

I had a guy build a Remington 700 in 7 rum. He talked me into using a PGT bolt that was real close to the dia. of the raceway. It all sounded good, but he didn't check the protrusion of the firing pin. I shoot like crap and it took me a while to figure it out. I was sitting at the bench and decided to watch the bolt instead of the scope. I could watch the firing pin drop and decided to try it with another rifle as it seemed to me you shouldn't be able to see it hit the primer. I couldn't see it on the other rifle, it all happened too fast and recoil interrupted the eye sight. Greg Tannel fixed it and it shoots good now. Would a bunch of shots through the chronograph tell you if you have a problem? A short firing pin (at least in my gun) caused a hang fire. I don't know if your situation is the same, but I am sure the chrono would tell if you had a hang fire. Maybe also just inconsistent ignition?
 
All of my chrony work didn't indicate an issue. Infact i was readily obtaining single digit ES and very uniform speed.

Adam
 
alinwa said:
Can someone just tell this man that firing pins aren't "pierced"......EVER???

They're "blanked,"

you can't "pierce" a primer cup with a firing pin.

Even with 1/8" of fall.

Turds in the catbox is one thing but this is just WRONG and takes from a good discussion.
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Thanks al....for your kind reply...... reminds me of others who no longer post on this site...... stool and mikeinco
 
I'm no expert on the subject but we make our actions with 0.200" free travel and 0.050" protrusion. Spring force is typically 22 lbs. Seems to work well on the 20+ we've built.

-Lee
www.singleactions.com
 
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B.Larson said:
Thanks al....for your kind reply...... reminds me of others who no longer post on this site...... stool and mikeinco
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Sorry Blarson but stool and mikeinco are not "others," they're names used by one person who had to change names because guys like you thought he was "mean."

If you'd really searched and understood this subject you'd know that no firing pin has ever poked a hole in no primer.......EVER..... even if you can find opinions to the contrary. Unfounded opinions, un-TESTED opinions, but knee-jerk opinions nonetheless.

In simple fact, the reason I no longer post much here is because people like yourself find this "diversity of opinion" to be more interesting and more "fair" than tested facts.

And more important than safety.


sad

easy, the liberal way is ever filled with support......mob mentality is The New World Order.... garner enough supporting "friends" and you must, by fiat be "right," right?

but sad

Facts aren't up for vote, thankfully! (Although "support" is, sadly. And few care to differentiate)

Go freaking TEST IT before spouting opinions here!!! I'll know you're telling the truth when you tell us how you killed the primers used in the testing regimen.

The op asks a good question, relevant, it needn't be clouded by digressions into banality. Experts across the world, REAL experts, shooters and builders, have documented differences in ignition due to firing pin fall variation. I know of several people who get paid to address this very real issue for shooters in the BR community, and not ONE of them has ever "pierced" a primer. I've spoken with the authors of some of the best books and articles ever written on the subject of accuracy regarding the effect of the firing pin fall/protrusion/diameter/spring weight on accuracy. I know of several systems purposely DESIGNED and built to address this specific topic.......

And none of THEM has ever poked a hole in a primer either...


al
 
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