Firing pin spring weight

[Grimstod]

So I bushed the firing pins in a lot of my rifles. Now that I do not need as much firing pin pressure how should I go about reducing firing pin pressure. I figure I would just grind down the end of the springs but I do not want to grind to far. How do I know I am getting close?

 

[Dans40X]

Measure twice
Cut once

 

[Grimstod]

Measure twice
Cut once

What do you measure?

 

[LHSmith]

How does bushing the FP hole ( in the manner normally done) cause too much spring pressure ?

 

[Grimstod]

Because you now have a smaller firing pin you do not need as much pressure to dimple the primer deep enough to start the sequence.

 

[LHSmith]

Because you now have a smaller firing pin you do not need as much pressure to dimple the primer deep enough to start the sequence.

Still don't follow. Normally the hole is reduced to closer tolerance with the FP. I see on Gre-tan's site he also offers to turn the FP tip. I assume he does this to get the ultimate match between the hole and the pin. I don't see how this minor reduction calls for reduced spring pressure.

 

[Grimstod]

Original firing pin was .098 I reduced it to .062 that is a 60% reduction in surface area. With 60% less firing pin surface needed to punch into the primer you need a lot less pressure.

 

[ppaul]

If it were me I would consult Greg Tannel before I did anything and see what an expert says. My .02.

 

[carlsbad]

Grimstod is exactly right. You need less force to punch the primer. More importantly, there is less pressure force trying to push the primer back out.

I don't normally reduce the spring force but you certainly can and I would like to try it too.

There is no formula that I know of for shortening a spring. But springs are cheap so you can do some experimenting.

A better solution would be to find a "softer" spring with a lower k value (F=kx from high school physics). Custom rifles often use a softer spring to make the bolt easier to operate since this is generally what a buyer does just before saying "wow, I'll take it". I've replaced several of these springs when owners have problems with ignition. They generally don't want to bush the bolt in their fancy custom.

So most springs for sale out there are stiffer, to fix just the problem mentioned above. If you find a source for softer springs let me know. I bush a lot of firing pins.

--Jerry

 

[Raythemanroe]

I don't believe reducing spring pressure or pin fall is a benefit.. You want a consistent pin fall center of the primer every time.. A strong positive ignition..


Ray

 

[butchlambert]

Ray is right. Dwight Scott and others have helped ignition on BR receivers by adding a tungsten weight to the firing pin. I have a tungsten weight on my Bat.

 

[LHSmith]

Why would one reduce the FP diameter so drastically to cause the problem in the first place?

 

[Grimstod]

Why would one reduce the FP diameter so drastically to cause the problem in the first place?

Oversized firing pins blow primers.

 

[jr600yd]

If it works now I'd leave it alone.

 

[butchlambert]

Why would one reduce the FP diameter so drastically to cause the problem in the first place?

You might do a search on BR.com about a thread in which explains the reasoning and math for the smaller diameter firing pins. It was written by Jerry Stiller. Jerry is an engineer. I'm not in favor of lightening or increasing the firing pin springs tension.

 

[Robert]

Shortening a spring is not a good idea. Springs have squared end and ground. Cutting the end coil makes the end out of square and the spring not compressing straight.


Effectively, a .0625 tip require less ENERGY than a larger one.

See http://c-g-designs.blog4ever.com/articles?page=22 and scroll down to 'On the question of F.P diameter.

R.G.C

 

[carlsbad]

While watching TV tonight I searched the internet for a softer spring without success. I was reminded of one safety feature; the stock spring is designed to go solid not far past cocked position to limit travel with a pierced primer. I don't think most aftermarket springs maintain this feature to the same extent and it doesn't seem like a critical safety function to me--an extra 1/4" of travel.

Gretan sells springs for $2 so it is easy to stock up on them. I've got a few. They are strong, perhaps a little stronger than the stock springs. I'll probably try a shortened spring soon and see what my results are.

I have found softer springs installed in custom rifles--stiller for one. Indeed it does make the action operate smoothly. I have one of these springs I took out of a rifle and replaced for a shooter who was having ignition problems. Gretan spring fixed his problem. But his pin hadn't been bushed. If you can find a replacement spring for these actions it will be smoother.

Also, adjusting your ignition timing to eliminate cock-on-close and reducing the size of the bump that keeps the cocking piece in place will also smooth the action out a lot.

--Jerry

 

[carlsbad]

Original firing pin was .098 I reduced it to .062 that is a 60% reduction in surface area. With 60% less firing pin surface needed to punch into the primer you need a lot less pressure.

Just noticed this. If original firing pin was .098, then it isn't a remington and you're even less likely to find a spring for it.

--Jerry

 

[Robert]

While watching TV tonight I searched the internet for a softer spring without success. I was reminded of one safety feature; the stock spring is designed to go solid not far past cocked position to limit travel with a pierced primer. I don't think most aftermarket springs maintain this feature to the same extent and it doesn't seem like a critical safety function to me--an extra 1/4" of travel.

Gretan sells springs for $2 so it is easy to stock up on them. I've got a few. They are strong, perhaps a little stronger than the stock springs. I'll probably try a shortened spring soon and see what my results are.

I have found softer springs installed in custom rifles--stiller for one. Indeed it does make the action operate smoothly. I have one of these springs I took out of a rifle and replaced for a shooter who was having ignition problems. Gretan spring fixed his problem. But his pin hadn't been bushed. If you can find a replacement spring for these actions it will be smoother.

Also, adjusting your ignition timing to eliminate cock-on-close and reducing the size of the bump that keeps the cocking piece in place will also smooth the action out a lot.

--Jerry

Jerry,

If a FP spring was designed to function solid close to cocked position, it would not survive the first blowback. It would also quickly lose its initial energy.

They usually work at some 2/3 of their nominal free lenght where their maximal force is obtained and, shorter than this, there is no rate increase and this make bolt lift easier as there is no force increase between decocked and cocked positions.

Solid lenght is often inferior to half the nominal lenght.

Reducing the size of the bump that keeps the cocking piece in place will perhapd smoothen bolt lift, but create a really serious potential danger, IMHO.

R.G .C

 

[carlsbad]

Robert,
Read my post again. They only go solid in the event of a primer failure.

FYI. Here are some dimensions on the stock remington short action spring:

Free length: 5"
Solid Length: 2.150"
Length in fired Position: 2.825"
Cocked length: 2.550
OD .400"
ID .290"
Spring rate (measured) 12.5 lb/in

I checked my Stiller spring and found these differneces:

Free length: 4.5"
Solid Length: 1.625"
Length in fired Position: 2.825"
Cocked length: 2.550
OD .406"
ID .305"
Spring rate (measured) 12.5 lb/in

I was surprised to find the spring out of the stiller to be the same spring rate.

I understand you have your opinions. Are you a lawyer? Because lawyers have more input into the depth of that bump than engineers do. Do you think benchrest triggers are a significant safety hazard? Realize the bump is the same depth for hunting rifles, tactical rifles, and every Remington 700 rifle. To reduce it's depth on a benchrest rifle is a common practice and creates much less hazard, IMHO, than a 2 oz trigger.

--Jerry