Gunsmithing Firing Pin Spring Strength...

mdesign · Jul 12, 2010

most of us have seen the firing pin/spring kits that promise faster lock time and better accuracy but it is my experience that this does not work as well as advertised. besides not improving accuracy there are other downsides and the bolt is harder to cycle.

My question is does anyone know how weak of a spring can I use on a 700 action and still still have reliable ignition? It looks like many of the springs are advertised at 18-20 lbs with the stronger ones in the lower 20's.

Can one buy a spring rated for 10-12 lbs? Is there ever been testing that identified a minimum reliable poundage? Seems it would not hurt accuracy.

kill_goose · Jul 12, 2010

Re: Firing Pin Spring Strength...

I dont know about minimum. But I recently put an after market firing pin assembly from Callahan in a 700.

At 26 lbs the spring made cycling the action VERY difficult, and if not lubed heavily on the rear of the bolt made it near impossible.

It has since been reduced to just under 20 lbs and is much more user friendly.

I personally see no advantage to going heavier than 20 lbs. But on the flip-side see no advantage to going extremely low either.

308sako · Jul 13, 2010

Re: Firing Pin Spring Strength...

deleted in protest

wnroscoe · Jul 13, 2010

Re: Firing Pin Spring Strength...

Cocking piece to sear bar hand off and cocking piece revile in the cocked position is crucial to felt bolt lift resistance. The cocking ramp angle is another area that when properly addressed bolt lift is very smooth. I've found that when this was addressed the standard 700 spring was sufficient and bolt lift was smooth and provided reliable ignition.

The speed lock system that employees an aluminum firing pin body and stiffer spring to decrease lock time increases bolt lift dramatically. My money's on the OEM parts and a little TLC to key surfaces.

BlackOps Tech · Jul 13, 2010

Re: Firing Pin Spring Strength...

I typically use a 24 or 28 lb spring with steel firing pin. I personally believe the lighter, reduced lock time pins are rather gimmicky and Roscoe has touched on a few other key areas to look at and give attention to. I believe you may be surprised at how smooth bolt lift can be when these areas are properly addressed and Defiance has stepped up with some new technology in the machining of the cocking ramp.

I would check with Wolff about different weight springs. The springs are cheap enough to play with different combinations, but I've had very good results with the 24 or 28 lb springs....

sobrbiker883 · Jul 13, 2010

Re: Firing Pin Spring Strength...

I've had extraction cam surface galling on one 700 after installing a "Blitzschnell" spring. Maybe the heat treat on that receiver/bolt was off, but I think the heavier spring had something to do with it......

BlackOps Tech · Jul 13, 2010

Re: Firing Pin Spring Strength...

I've seen that numerous times without the Blitzschnell spring. There are usually other issues that exist and the heavier springs aren't typically what causes it. With proper bolt timing, primary extraction cam angles and properly prepped cocking ramp, the galling shouldn't be there....I've also dug ditches in the extraction cam on a few custom actions with standard weight springs....

stiller · Jul 13, 2010

Re: Firing Pin Spring Strength...

Dont go less than about 20 lbs, especially if running magnum primers. You will start getting ignition issues that will show up as flyers. One of our customers run a test for us that showed 19 lbs was the requirement for even ignition using small rifle federals. This poundage is highly dependent on how much the firing pin falls, about .250 for a factory Rem. If you drop less you need much more force and it still isnt real reliable. The fast lock time pins work fine if there is no drag in the system, and there usually isnt. If there is drag it should be fixed anyway. The lower mass is offset by the higher velocity of the pin. The math will show that it has equal momentum and slightly more energy. I prefer them myself. If the cocking ramp is not smooth, you will get some additional friction when lifting the bolt. You can always lap the surfaces together with a light spring, clean it up real well and grease it. You should always grease this area by the way.

I'm not exactly sure how the firing spring effects the extraction cam on the action though. All the motion and forces that occur due to the spring are between the cocking piece and the bolt. The extraction cam doesnt come into play because there is no force pushing the bolt forward into it.

Keith Johns · Jul 13, 2010

Re: Firing Pin Spring Strength...

The springs from PT&G seem to be great. Not sure if theyre stronger, but they are different than factory, you can tell just by looking at the coils.

The Tubb Speedlock kits I do not like becuase when I used one the spring was all bunched up in the bolt and rubbed on the body on bolt lift. Felt like shit.

Never had a problem or concern with PT&Gs assemblies. I use them and have installed a few. Never heard or anything wrong.

Shroud needs to be greased right, esp. if it's aluminum.

btw, what about using just an aluminum pin without the stiffer bound up spring? Youd still get faster locktime would you not?

BlackOps Tech · Jul 13, 2010

Re: Firing Pin Spring Strength...

Try removing the trigger from the action, leave the FP in place and cam the bolt open. If any of the things I mentioned has an issue, it will typically show up on the extraction cam.

stiller · Jul 13, 2010

Re: Firing Pin Spring Strength...

If you remove the trigger from some Remingtons and try to cock it, it will bind up because the trigger side plates are what guide the cocking piece. The early ones especially wont open. I guess if you do this and try to force up on the bolt handle it will eventually hit the extraction cam and load it hard. I wouldnt put that to being a problem though as it shouldnt be done. On most customs I haven't noticed this problem as the cocking slot is not notched. There is nothing in the trigger that pushes the bolt forward to put load on the extraction cams. If the trigger isnt pulled and is ready to fire, it actually pulls the bolt back and keeps the extraction cams apart. I really dont see any interaction between the cocking ramp on the bolt, the extraction cams and the bolt lug cams. As long as the bolt rotates and there is no interference between the extraction and lug cams, they really dont depend on each other. Each one has a separate task. The lug cams push the cartridge into the chamber. The extraction cam pulls it back out. The firing pin ramp only pulls back the pin. I've built about 10,000 actions and actuate and look at every one of these as I do. I am not sure exactly what I am missing.

BlackOps Tech · Jul 13, 2010

Re: Firing Pin Spring Strength...

I'll avoid a long disertation on this, as this isn't my post and it's steering away from what the OP intended, but the bottom line is, any action, especially a custom, should operate just as smoothly without the trigger installed. I don't have this issue (or any for that matter) with the Skunkworks actions, but I've seen numerous others, custom and OEM alike, that I've repaired because of "ditch digging" on the extraction cam. I can't speak to what you're missing either, but the trigger shouldn't be a stop gap to breaking something in an action just by opening the bolt....Thanks for your input Jerry and I hope you figure it out....

Keith Johns · Jul 13, 2010

Re: Firing Pin Spring Strength...

mdesign, just order springs from PT&G and dont worry about them anymore.

If its still hard to open with a PT&G spring, then the spring isnt your problem, and it could be any number of things.

stiller · Jul 13, 2010

Re: Firing Pin Spring Strength...

Overall, I really dont think I am missing much. The system is pretty simple to understand. I agree that having to have the trigger in the action is kind of a hassle, but when Mike Walker designed the Rem 700 he apparently didnt think it much mattered. I made sure our actions didnt need the trigger installed for ease of use when selling actions by themselves.

If you really want good extraction and firing pin ramps, you have to generate them with mirrored code on the 4th axis cnc. That way they exactly match each other and mimic the way the bolt is used. We have always done them that way. If they are cut 2 dimensionally on either part, it is a compromise.

mdesign. If you want a few springs to play with email me your address with what your action is, long or short. I will send you a few springs gratias. Our springs are the same as the PT&G springs, they bought them from me. They are specifically designed for my bolt, but work in a Rem too. They can be cut and tuned in to a lower force, but I dont recommend it. Hopefully this small departure from the original post informed some of the readers of the intricacies of the bolt fits etc.

Keith Johns · Jul 13, 2010

Re: Firing Pin Spring Strength...

Take Mr. Stiller up on his offer, or get some from PT&G for $4.
Dont cut them. They work great as is.

Or send the bolt to me for a new assembly

mdesign · Jul 13, 2010

Re: Firing Pin Spring Strength...

Thanks Jerry, very generous of you...I sent you a PM with the info but I will have to say that I own one of your actions and it is the smoothest cycling action I have.

Roscoe - I wish I understood this cam angle thing better. Are we talking the cam on the bolt handle??

AZP - I have cycled the bolt with the trigger off and is smoother but I chalked it up to not having to compress the spring. Yes, I could send you the bolt but man a guy has to learn a few things is life for himself, can't hire it all done.

wnroscoe · Jul 13, 2010

Re: Firing Pin Spring Strength...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mdesign</div><div class="ubbcode-body">Roscoe - I wish I understood this cam angle thing better. Are we talking the cam on the bolt handle??</div></div>

The cocking ramp is in the bolt body and is what the striker/cocking piece travels up while the handle is being lifted as to re-cock the mechanism for the next shot. A smooth cocking ramp is but just one part of the equation but it does help to have it polished.

mdesign · Jul 13, 2010

Re: Firing Pin Spring Strength...

Got it! Sort of forgot about that cam for a minute.

Keith Johns · Jul 13, 2010

Re: Firing Pin Spring Strength...

Ya I was just jokin about sending it to me. You'll get it taken care of.

And you say its easier to lift with no trigger in? your still expanding the spring. The cocking piece is still riding up the bolts cocking cam on lift, trigger or not.

To me most Remys feel harder to open with no trigger in.

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Gunsmithing Firing Pin Spring Strength...

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