Firing Pin Travel

[Robinhood]

Working on a bolt that is harsh to open. I have made some improvements and now I'm down to decrease the over cocking. What is the optimal firing pin travel you guys are setting the cocking piece to allow. I know that it may effect the lock time I am just curious if anyone had a set length or if they set each one to the trigger and sear. Let me know if I'm chasing a red herring.

[earl39]

If i remember correctly the couple i have changed i went with .035 protrusion.

[Robinhood]

Thanks Earl. Protrusion is the amount the nose of the firing pin stands out in relation to the face of the bolt head.

I was looking for total amount of travel of the firing pin. When rifle is ready to shoot the sear is engaged to the trigger. The cocking pin is being held by the sear ready to fire. When you pull the trigger the firing pin is released and travels until it impacts the end of the bolt head. That distance is what I am after.

[BillPa]

When you pull the trigger the firing pin is released and travels until it impacts the end of the bolt head. That distance is what I am after.

There are two pin fall lengths, what its set to on the bench and when it strikes a primer which is the important one. When a pin strikes a primer it stops the pin at ~.020" protrusion regardless what its set to on the bench, why some of us set them to .030"-.035" max. Anything longer only serves to shorten the pin fall and reduce primer impact energy.

With that said, after setting the protrusion to 30-35 I'll adjust the cocking piece so the cocking piece pin has minimum clearance at the bottom of the cocking ramp in the fired position. Although it will never bottom out the minimal clearance allows for max spring compression when cocking the bolt.

Bill

[Robinhood]

Thanks Bill, I have been doing that exact thing. Doing so guarantees the longest possible engagement of the cocking ramp and the cocking pin when lifting the bolt. With the factory angle that can make for a heavy lift. I have some factory bolts that I polished on that are smooth. They don't feel like the timed and trued actions but smooth. I have modified the ramp and the effort was reduced but since it was done by hand it is not as smooth as the SSS T&T but definitely lighter lift. I have a lot of time on my hands and I'm just fiddle farting around and was wondering if adjusting the travel to a shorter stroke would make a difference. So today I'm going to play with that an see what happens to lock time and force. If it lights the primers off and the lock time is not adversely effected it should be good, eh?

[BillPa]

and was wondering if adjusting the travel to a shorter stroke would make a difference.

Oh it will, but it will also shorten the pin fall length and the amount of spring per-compression. The amount of pin fall is determined by the length of the cocking ramp excluding any over/under cocking at sear hand off. In fact you can back the cocking piece off enough the pin won't be moved at all when cocking the bolt.

Bill

[BigDave]

This thread is not that old. So, I will add this very interesting link. The article agrees with .035". It also mentions overall spring length and some tips for adjusting things.

http://www.savageshooters.com/conten...rotrusion-Data

[hothead]

Not to start an argument, but I was told by a member of Team Savage F/tr team to set protrusion at .060. which I did. I am shooting very stout loads
in the 308 from the Savage custom shop and primers look good. I'm shooting 155.5 gr Berger's at 3070 fps. just to say how hot of a load it is.
I have no cratered primers. the rifle is shooting awesome. like .4 moa at 300 yards for 10 shot groups.
hh

[BigDave]

My firing pin was set at .048" by the factory. I re set it to .036 since I have no plans to shoot any surplus or any hard primered ammo at all. I adjusted the spring length to 1.92". That gave me about .02 clearance on the bolt cam from touching the bolt body.

That is about as fast as you will get unless you replace the firing pin spring with an extra strength Wolf spring.

It is hard enough to get a stock spring re installed with no help. A Wolf spring would need a home made jig (I have seen one I liked using a socket set into a block of wood to hold the firing pin). A third hand/second person would be most helpful when installing either spring. It is not a whole lot of fun. I gashed my thumb a bit when I did it by myself.

I read that grease and oil on the spring and/or firing pin assembly actually serve to slow it down. It is supposed to be pretty dry. I dont know why or how this is true. Can anyone comment on this last thing I mentioned?

I took apart and low speed polished (with out heating the metal) every part of my firing pin assembly including the spring coils. That must help with velocity of the pin I would imagine.
Hope this helps to answer your question.

[sharpshooter]

Why would you want to add more strength to the spring?

[BigDave]

Why would you want to add more strength to the spring?

I personally would not. Stock Savage Spring rate is 26lbs. A wolf enhanced spring is 32 lbs. Claims of faster lock up time with Wolf. Claims of elimination of light primer strikes with Wolf. Some people claim that Wolf spring doesn't do anything except make the bolt lift even harder! Here is some reading. I never wanted a Wolf. After reading more about it, I want one even less and I would warn people against it.

http://www.savageshooters.com/showth...ht=WOLF+SPRING
http://www.savageshooters.com/showth...ed-from-Savage
http://www.midwayusa.com/product/474...g-action-32-lb

You decide. I couldnt imagine trying to install the darn thing(the Wolf). A stock 26 lb is plenty hard to install alone. My thumb still hurts!

[BillPa]

Not to start an argument, but I was told by a member of Team Savage F/tr team to set protrusion at .060.

I have no cratered primers.
hh

The pin protrusion has nothing to due with cratering-blanking primers, its a result of the pin to pin hole fit, the tip profile, insufficient spring tension to support the indentation, the primer cup or a combination of them.

Sharpshooter has (tried?) educated us a few dozen times why less equals more where pin protrusion is concerned.

You, I or anyone else will ever indent a primer more than about .020", the anvil stops the pin forward at that protrusion length regardless if it set longer on the bench.

A firing pin isn't instantly accelerated to X velocity by the spring, it ramps the pin up in speed. Anything that reduces it fall length or restricts it's fall also reduces it's impact energy, that E=M*V thing. Round numbers, with pin set to .060" protrusion the pin fall length is shortened .040" when it strikes a primer whereas one set to .030"-.035" its fall length is only reduced .010-.015" allowing more time for the pin to accelerate thus increasing it's impact energy.


Bill