Firing pin spring weight

[carlsbad]

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?

Grimstod,
Now that I know the spring rate, and length I can tell you how to calculate the effect of shortening the spring:

Count the active coils. The Remington SA has 36 coils. Shortening it actually INCREASES the spring rate. Each coil is worth approximately 1/36 of the spring rate. Lets call it .028. shortening the spring, however, reduces the compression and thus reduces the total force.

So you increase the spring rate by 2.8% for each coil you cut off. But you decrease the compressed length by 5/36= .139" per coil. Lets say nominal compression is 5" -3" =2", then F=Kx give a force of 2" x 12.5 in/lb = 25 lbs for the unmodified spring.

Shorten by one coil and your new force is (2-.139") x 12.5 x 1.028 = 23.9 lbs about 4 1/2 % decrease.

2 coils: 22.7 lbs 9%

3 coils: 13.5%

etc. I've made some approximations to make the arithmetic easier so this will lose accuracy at more say 5 or so coils. It's still be close enough.

I wouldn't go shorter than 4" to ensure the spring is in the proper working range.

I don't see significant safety issue doing this work other than you can create FTF events. Treat those with the same safety practices you would normally. I really don't expect any unless you get carried away. Because your pin diameter is so much reduced, your force/unit area at the firing pin is still going to be higher than stock so I don't think you'll reduce your ignition reliability and don't think you'll reduce your accuracy. But of course you should test and let the paper tell you. I'd be very interested in your results. This winter I'll likely try a shorter spring and post he results.

--Jerry

 

[Grimstod]

Grimstod,
Now that I know the spring rate, and length I can tell you how to calculate the effect of shortening the spring:

Count the active coils. The Remington SA has 36 coils. Shortening it actually INCREASES the spring rate. Each coil is worth approximately 1/36 of the spring rate. Lets call it .028. shortening the spring, however, reduces the compression and thus reduces the total force.

So you increase the spring rate by 2.8% for each coil you cut off. But you decrease the compressed length by 5/36= .139" per coil. Lets say nominal compression is 5" -3" =2", then F=Kx give a force of 2" x 12.5 in/lb = 25 lbs for the unmodified spring.

Shorten by one coil and your new force is (2-.139") x 12.5 x 1.028 = 23.9 lbs about 4 1/2 % decrease.

2 coils: 22.7 lbs 9%

3 coils: 13.5%

etc. I've made some approximations to make the arithmetic easier so this will lose accuracy at more say 5 or so coils. It's still be close enough.

I wouldn't go shorter than 4" to ensure the spring is in the proper working range.

I don't see significant safety issue doing this work other than you can create FTF events. Treat those with the same safety practices you would normally. I really don't expect any unless you get carried away. Because your pin diameter is so much reduced, your force/unit area at the firing pin is still going to be higher than stock so I don't think you'll reduce your ignition reliability and don't think you'll reduce your accuracy. But of course you should test and let the paper tell you. I'd be very interested in your results. This winter I'll likely try a shorter spring and post he results.

--Jerry

Finally a good answer. Thanks Jerry I am fining this away to on my computer for future reference.

 

[Robert]

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: 2.875"
Cocked length: 3.050
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: 2.875"
Cocked length: 3.050
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 safeties 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

Jerry,
No, I was not a lawyer, simply engineer with a degree in industrial safety and accident prevention. One of my duties was the industrial rik management for an european aluminium company in 4 countries. My point is probably Professional deformation.??..

Don't you think there is no potential risk if a FP spring is allowed to be compressed to solid in case of a blowback?. The sear then protuding would come quite close to the glasses?.

Agree 100% on 2 ounces triggers and I think here I quite know what I am talhing about.
R.

 

[Alex Wheeler]

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

but create a really serious potential danger, IMHO.

???

 

[hogpatrol]

Good Morning America! What can we overthink today?

 

[USMCDOC]

My only question is: If you have reduced the amount of pressure to move the firing pin assembly forward to strike the primer, have you not also increased your lock time?

 

[carlsbad]

Good Morning America! What can we overthink today?

I see a lot of incorrect science posted on this forum. I see guys say 'ask the expert" and then reference someone they trust but who has absolutely no engineering ability. So I post the engineering and it's called "overthinking".

This is why engineers have no social life.

--Jerry

 

[BoydAllen]

My Viper action came with a small firing pin tip. It came with a cut down spring that gave a cocked weight of about 19#. I have primarily use Federal small rifle primers but I have used others and I have had no problem with any of them. Currently I have a Tubb dual spring setup in its bolt. It gives a cocked weight that is about 25# but because it eliminates the need for the spring to rotate against the shroud and pin flange as it is cocked the effort to cock is reduced in the top half of the handle stroke. Another option that I have tried is one of Greg Tannel's relatively new springs that has smaller gauge wire and more coils so that there is less stack during cocking. These are quite inexpensive and they reduce cocking effort as well. This should give you some options to try. Based on my experience you should have noting to worry about on pin weight or spring weight down to a cocked weight of #19 because I have also played with one of the Tannel Aluminum shaft pins. I should add that my Viper has significantly less pin fall than your Remington, so what works for me should be good to go for you, assuming you do not have drag problems due to a loose fitting shroud. If you want to test for that assemble your bolt without the firing pin spring and tip it end for end listening for the pins fall while pressing on the shroud from all four sides. I would be particularly concerned about what happens when you press the shroud up like it is when the action is cocked. Pacific Gauge and Tool makes an oversized shroud that is large behind the threaded portion that you can fit so as to improve this situation. Speedy Gonzales asked Dave Kiff to make them years back and they are still available.

 

[LHSmith]

Well, we really don't know what brand/ model rifle(s) the OP is working on.....or what actual problem these mods are attempting to correct. All we know is the FP original diameter was 0.098".

 

[Raythemanroe]

I see a lot of incorrect science posted on this forum. I see guys say 'ask the expert" and then reference someone they trust but who has absolutely no engineering ability. So I post the engineering and it's called "overthinking".

This is why engineers have no social life.

--Jerry

I watched two engineers fail to change a flat tire once (true story).. They couldn't figure out why the manufacturer didn't supply a tool to fit the wheel nut.. They had the tire iron, scissor Jack, spare and everything sprawled all over but couldn't figure it out.. Apparently they didn't have a degree in common sense.. I stopped screwing with pin weight and springs to improve lock time when I watched accuracy degrade..

Ray

 

[hogpatrol]

 

[butchlambert]

You might want to pay attention to Robert. I'll bet he can air up a tire or change it if necessary.

 

[carlsbad]

Jerry,
No, I was not a lawyer, simply engineer with a degree in industrial safety and accident prevention. One of my duties was the industrial rik management for an european aluminium company in 4 countries. My point is probably Professional deformation.??..

Don't you think there is no potential risk if a FP spring is allowed to be compressed to solid in case of a blowback?. The sear then protuding would come quite close to the glasses?.

Agree 100% on 2 ounces triggers and I think here I quite know what I am talhing about.
R.

robert,
Can't tell if we agree or disagree. I see you're in Normandy. Unfortunately, your English is much better than my French so we'll continue in English.

The design, by Remington, is that the spring will go solid and limit the travel of the cocking piece so that it's travel out the back of the bolt is limited to about 1/2". As you can see, the stiller spring numbers above allow the spring to extend about another 1/2". So this is a safety feature that is compromised by Stiller and possibly other aftermarket springs. That said, in precision shooting with a scope, the eye and check is generally far behind the cocking piece and out of danger. I don't see the solid length given on most replacement springs. I brought this up since this is a safety feature of the Remington 700 that is sometimes compromised....we discussed in another thread the 3 rings of steel, a 100x more important safety feature that is also often compromised by other designs.

I thought your original point was the depth of the detent that the cocking piece falls in. That is why I brought up the 2 oz trigger.

--Jerry

I watched two engineers fail to change a flat tire once (true story).. They couldn't figure out why the manufacturer didn't supply a tool to fit the wheel nut.. They had the tire iron, scissor Jack, spare and everything sprawled all over but couldn't figure it out.. Apparently they didn't have a degree in common sense.. I stopped screwing with pin weight and springs to improve lock time when I watched accuracy degrade..

Ray

Ray,
Yep, they'll give an engineering degree to almost anyone who pays tuition and goes to class. Only a few of us have "the Knack". I'd still be a virgin if there weren't some women looking for predictable stability engineers provide. --Jerry

 

[Alex Wheeler]

I'm still waiting for someone to explain to me how reducing the bump after the notch at the top of the cocking ramp has any effect on safety.

 

[Robert]

You might want to pay attention to Robert. I'll bet he can air up a tire or change it if necessary.

Thank you, Butch..

Here,even engineers does not need to know how to change a tire...Just ring your motor insurance company and, whitin half an hour, a mechanc show up and do the job for you..LOL
Sncerely yours.
R.G.C

 

[M995]

LRobert,
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: 2.875"
Cocked length: 3.050
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: 2.875"
Cocked length: 3.050
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 safeties 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. For future reference

 

[Eddie Harren]

1. An engineer dies and reports to the pearly gates. St. Peter checks his dossier and says, “Ah, you’re an engineer, you’re in the wrong place.”
   
   So the engineer reports to the gates of hell and is let in. Pretty soon, the engineer gets dissatisfied with the level of comfort in hell, and starts designing and building improvements.
   
   After a while, they’ve got air conditioning, flush toilets and escalators, and the engineer is becoming a pretty popular guy.
   
   One day God calls Satan up on the telephone and asks with a sneer, “So, how’s it going down there in hell?”
   
   Satan replies, “Hey, things are going great. We’ve got air conditioning, flush toilets and escalators, and there’s no telling what this engineer is going to come up with next.”
   
   God replies, “What? You’ve got an engineer? That’s a mistake, he should never have gotten down there, send him up here.”
   
   Satan says, “No way! I like having an engineer on the staff, and I’m keeping him.”
   
   God says, “Send him back up here or I’ll sue.”
   
   Satan laughs uproariously and answers, “Yeah right. And just where are you going to get a lawyer?”

 

[carlsbad]

LRobert,
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:

....

--Jerry. For future reference

M995,
The Cocked length is wrong in your post. I woke up the next morning and realized before I got out of bed that I'd added firing pin fall instead of subtracting it and fixed it. You must have made a copy in the 5 hours I was sleeping. --Jerry

 

[Grimstod]

Well, we really don't know what brand/ model rifle(s) the OP is working on.....or what actual problem these mods are attempting to correct. All we know is the FP original diameter was 0.098".

My problem has been solved so I don't see why its needed. I do this for a number of guns anyway.

 

[Eddie Harren]

"..........I do this for a number of guns anyway."

Would they be those 1500 Yd. laser Mosins?