failure to fire

[fshooter]

Purchased a .308 F T/R and it does not fire on every shot. Checked headspace on rounds that did fire and new Lapua brass and there are within specs. Fired brass runs 0.004-0.008" over minimum using the Redding Instant Indicator. New brass runs 0.003-0.005" over minimum.
I can see a very faint primer firing pin imprint on the rounds that failed to fire. The ones that fired look normal. Primers are seated 0.001-0.002" below in the pocket.
I am thinking along the lines of a firing pin malfunction or failure to protrude far enough on release.
Would appreciate the advice of others who have experienced a similar problem.
Thanks

[irondog54]

How many rounds do you have through the gun? Have you ever had the bolt apart. My only guess would be carbon build up in the bolt assembly, specifically on the firing pin shoulder. I have only seen this in semi auto rifles, though. ???

[fatdaddy]

Your trigger is set too light. Make the pull just a bit heavier and the problem will disappear...Bill

[Blue Avenger]

have seen where in an effort to remove over travel on some triggers the clearance for sear travel could interfere and slow sear release travel. Not often but can happen. bolt release part of sear dragging on side of stock can do it also.

[GaCop]

It won't hurt to check FP protrusion. If ok, that's one less variable to consider.

[pdog06]

It won't hurt to check FP protrusion. If ok, that's one less variable to consider.


+1 You almost gotta start there to see if the Protrusion is set right.

[bigedp51]

You have a firing pin and a firing pin spring that makes the cartridge go bang, I may be missing something but the trigger isn't what strikes the primer it just "sets it free".

Some random long range mechanical physic ability possibilities.

1. You uniformed the primer pockets and the depth is set too deep.

2. New brass length to datum line is normally "under" minimum headspace of 1.630 to insure chambering, you could possibly have some very short cases.

3. Dirt, metal shavings, brass chips, dried or hard grease, broken firing pin spring or gremlins inside the bolt.

4. All of the above.

Dissemble the bolt and look for problems and clean, the firing pin spring could be catching or hanging on a bur or rough spot inside the bolt. On 50 plus year old milsurps its always dried cosmoline and debris inside the bolt that causes the misfires, without dissembling you will never know if any gremlins are inside. ;)

[sharpshooter]

It's an accutrigger problem. Set the trigger a little stiffer and your problem will disappear.

[pdog06]

Usually when an accutrigger gun fails to fire it is due to the trigger locking up on the accutrigger blade because of either being set too light or by using uneven force on the trigger, but the original poster never said the trigger locked up and had to be re-cocked. I was actually thinking of the pull weight as the problem until I saw he didnt mention anything about the trigger locking up.

Fred, If the pull weight is set too light will it sometimes also allow the trigger to feel like it functioned fine(I.E. not locking up on the trigger blade) but still not allow the gun to fire? Kinda like a timing issue or something maybe?

[sharpshooter]

Sometimes the blade return spring almost overpowers the trigger return spring and the trigger itself will move before the blade is pulled far enough back to clear the safety notch. When this happens, you can kinda feel a "kick back" from the accutrigger blade. When I run into this situation, I cut 2 coils from the blade return spring to relieve some of the tension. It only has to be strong enough to return reliably.