firing pin protrusion

[klayton83]

this may be a topic all of you have already discussed but i was wondering what the perfect amount of firing pin protrusion is. i am using br4 primers if that makes a difference. the other day i had one that would not go off and so i lofted the bolt and inspected replaced and fired it again, and it went off. i would like to know that my rifle will never do this again. so i would like to adjust the firing pin and i took the bolt apart and can see that it can be adjusted. i just don't know what safe maximum protrusion would be without rupturing primers? ...

[82boy]

Welcome to the site.
Maximum protrusion, is not a good thing, as this actualy cuts down on the total amount of actual firing pin travel. Want you want is enough firing pin protrusion, to have a constant ingnigtion. Paul Mauser beliefe was that you need .050 protrusion, and that is what most people accept as standard. Sharp Shooter has ran the numbers, done expermints, and with the modern componets use today and the savage design, there is no need for that much travel, and his thought is it should be much less.

[nwkman]

Not enough over travel in the trigger will cause missfires.

[82boy]

Not enough over travel in the trigger will cause missfires.


huh?

[earl39]

the other day i had one that would not go off and so i lofted the bolt and inspected replaced and fired it again, and it went off.

First did it show the firing pin strike? If it did the primer might not have been seated all the way down. If it didn't you might have had a false firing, i mean you triped the accu-trigger safety and need to unlock the bolt to reset the trigger.

[klayton83]

i do not have an accutriger its actually a stevens 200 (i know there is another section for that but....). it did show a strike on the primer. i adjusted it a little the other night and loaded a dummy round with a live primer and it put a deeper mark in it. i tested it like 3 times and they all went off. like i said this only happened once it is just that i don't want it to ever happen when i need it to go off. this is chambered in 6br and i am using lapua brass. i just don't want it to start causing primer puncture. i read that the accuracy internationals sometime puncture some of the softer primers because the weapon was intended for combat use. I don't want punctures but i definitely want that maximum reliability. also this was first run on this brass and i have never had it happen with previously fired brass. i am thinking the combat protrusion minus about .1 or .05 maybe perfect...... thoughts?

[klayton83]

i ment minus .01 or .005

[short round]

Over travel, which is set to close can cause accuracy problems. Some over travel may be needed, to prevent sear from dragging on top of trigger. Also bolt removal may be difficult. A little extra trigger travel is better than not enough. When adjusting firing pin, check cocking piece pin in fired position. There should be about 0.005" clearance between pin & bolt body. If set without clearance it will limit firing pin travel.

[Blue Avenger]

Not enough over travel in the trigger will cause missfires.


huh?
I think he is referring to the sear dragging on the trigger if things get to tight.

[klayton83]

i don't think that there is any problem with the trigger mechanism. I did notice that there needs to be a little more clearance between the cocking pin and the bottom of the well? i guess that is what you would call that. so i adjusted that and set the protrusion to about .03 protrusion and fired it on some once fired cases that are not live except for the primer and it looks like a good dent in the primer so i might see if i can find some time to load up about 100 and try it out. i guess if it is puncturing the primers i can always back it off some. but at least this way i will be guaranteed the round going off and not hearing that horrible click when i have my rifle on a coyote or deer.

[sharpshooter]

First off, you are never going to "puncture" a primer no matter what the protrusion is set at, unless of course the pin tip has a sharp point.
The tip of the firing pin will never indent the primer over about .025". It will bottom out on the anvil of the primer. Typically the protrusion is set from the factory at about .055", which is plenty long and all it does is limit the firing pin travel, giving less impact energy. .035" is optimum.

[klayton83]

thank you sharp shooter. i am guessing that this is fred a sss wow it is hard to get ahold of you. i guess that this forum is a better way to do it?

[thomae]

For what it's worth: The firing pin threads (at least the large diameter one that is in pieces on my workbench) are 28 TPI.

By doing the math, we find that when you adjust the firing pin, each quarter turn of adjustment equates to a change in protrusion (either more or less depending upon which way you turn) of 0.00893"

One full revolution equates to a change in firing pin protrusion of 0.035714"

All the best,
Thomae

[airaddict]

So could u strip down the firing pin and when you reassemble it, only screw it back on one turn or so and have the "optimum" firing lin protrusion? Ive never attemtped to disassemble one........yet......

Brian

[nsaqam]

So could u strip down the firing pin and when you reassemble it, only screw it back on one turn or so and have the "optimum" firing lin protrusion? Ive never attemtped to disassemble one........yet......

Brian


Nope.

Once you get the FP flush with the boltface THEN you can screw it in one more turn to get ~.035" protrusion.

[airaddict]

So the firing pin stop nut determines protrusion and the cocking piece determines the amount of whack the pin delivers? Is that about the jist of it?

Brian

[nsaqam]

The stop nut does indeed determine FP protrusion but the amount of whack is determined by a number of parts including the FP mainspring, the cocking ramp in the bolt body, and the position of the cocking pin.

[thomae]

So could u strip down the firing pin and when you reassemble it, only screw it back on one turn or so and have the "optimum" firing lin protrusion? Ive never attemtped to disassemble one........yet......
Brian

Nope.
Once you get the FP flush with the boltface THEN you can screw it in one more turn to get ~.035" protrusion.


Or, you could get lucky with your "calibrated eyeball." I put mine back together and then measured protrusion to see how I needed to adjust it. It measured right at .038. Done. No adjustment necessary (Although I will never be able to do that again in a million years!



The stop nut does indeed determine FP protrusion but the amount of whack is determined by a number of parts including the FP mainspring, the cocking ramp in the bolt body, and the position of the cocking pin.


With respect to the cocking piece and firing pin spring: I concur that they affect "amount of whack." However, I would suggest that the cocking ramp does not affect "amount of whack" as it serves only to get the cocking pin back far enough to be held in place by the sear. Any adjustment or change of the cocking pin/sear contact surface may change how far back the firing pin is compressed, and thus change the amount of "whack," but unless I am mistaken, no matter what it looks like, steep or shallow, rough or smooth, once the rifle is cocked, the cocking ramp does not play a part in firing the rifle. If I am mistaken, I am sure I will be swiftly and surely corrected. ;)