40X rimfire firing pin spring

[dstoenner]

After I got my rebarreled 40X action back, I started doing some ammo testing to see what the new barrel liked. I first tried Centr-x and Midas+ Groups were about 40% better than the original barrel. Then I tried Eley and the groups wer more than 50% improved, in fact 1 10 shot group was .670 at 100 yards. I was elated. BUT with Eley I had at least 1 and sometimes 2 FTF in a 10 shot group which then my match chamber turned them into also Failure to Extract.

I thought it over, before I rebarreled I had never had either issue. It was rock solid. I asked the gunsmith about it and the headspace. He said he set the headspace at .041 and he had no clue about the FTF. I had already checked the headspace with my go gauge and it wouldn't close on it so what he is saying is good data.

It left onlly one thing I could think of and that was the firing pin spring. I looked all over for a firing pin spring and finally found one at PT&G. I bought it. Put it into my bolt and went to the range to test. Now my beautiful groups were horrible with a couple of flyers in each batch of Eley that I tested making the groups at least 1.3 inches to one group was over 2!!! WHAT.

My guess is that the PT&G spring is too strong and it is doing too much to the case when it hits bottom. Here is a picture:\\


The short one is original and the long one is PT&G. I tried pushing down on the spring with my calipers and I could pretty easily collapse it .300 inches but the PT&G I could only get about .250 inches.

I am putting my original back in and retest to make sure the groups are still good. If so then I am left with a dilemma of what to do moving forward. I am looking for suggestions from those who might have faced this issue.

I think I have maybe 2 options

1) Get a firing pin spring off of ebay that was from some part gun on the hope that it might be just a little better.

2) Cut coils. The current is 2.25 inches. I could maybe cut the PT&G down to 2.500. That would give me a little more umph to hit the Eley and maybe not disturb the accuracy.

I know this is issue and solution are a fine balance of tune of the whole action. What would you do????

Thanks in advance

David

 

[Hi-NV Shooter]

After I got my rebarreled 40X action back, I started doing some ammo testing to see what the new barrel liked. I first tried Centr-x and Midas+ Groups were about 40% better than the original barrel. Then I tried Eley and the groups wer more than 50% improved, in fact 1 10 shot group was .670 at 100 yards. I was elated. BUT with Eley I had at least 1 and sometimes 2 FTF in a 10 shot group which then my match chamber turned them into also Failure to Extract.

I thought it over, before I rebarreled I had never had either issue. It was rock solid. I asked the gunsmith about it and the headspace. He said he set the headspace at .041 and he had no clue about the FTF. I had already checked the headspace with my go gauge and it wouldn't close on it so what he is saying is good data.

It left onlly one thing I could think of and that was the firing pin spring. I looked all over for a firing pin spring and finally found one at PT&G. I bought it. Put it into my bolt and went to the range to test. Now my beautiful groups were horrible with a couple of flyers in each batch of Eley that I tested making the groups at least 1.3 inches to one group was over 2!!! WHAT.

My guess is that the PT&G spring is too strong and it is doing too much to the case when it hits bottom. Here is a picture:\\
View attachment 1301856

The short one is original and the long one is PT&G. I tried pushing down on the spring with my calipers and I could pretty easily collapse it .300 inches but the PT&G I could only get about .250 inches.

I am putting my original back in and retest to make sure the groups are still good. If so then I am left with a dilemma of what to do moving forward. I am looking for suggestions from those who might have faced this issue.

I think I have maybe 2 options

1) Get a firing pin spring off of ebay that was from some part gun on the hope that it might be just a little better.

2) Cut coils. The current is 2.25 inches. I could maybe cut the PT&G down to 2.500. That would give me a little more umph to hit the Eley and maybe not disturb the accuracy.

I know this is issue and solution are a fine balance of tune of the whole action. What would you do????

Thanks in advance

David

Wolff sells springs for the 40X RF they have 18-lb. as factory for reference. they have both a 26-lb. and 30-lb. I would trim some coils off the one you have now. count the coils and not what the measured length is when comparing springs.
what is happening is you are over driving the firing pin. also 0.041 HS seems a bit tight most use 0.043 and even up to 0.045

Lee

 

[MrG52D]

I would cut 2-1/2 coils off the PT&G spring ( off the unfinished end ), then grind a 1/2 coil off to make it sit flat. That would put the number of coils at 17, the same as the old spring. Unless the profile of the pin tip has been altered, this should put it back close to the day it was new. A larger footprint on the pin, will require a bit more spring to drive it properly.

 

[pintopete]

Is the diameter of the wire the same on the two springs? I suppose if you had an arbor press and a scale, you could compress each a set and equal amount, and then get a number for fair comparison. Ideally you would compress the springs the same amount as when installed, and then a second time compressed when installed and cocked.

”Cutting coils does increase the spring rate. The only thing that will change will be the length of the wire used to wind the spring. The longer the wire is the lower the spring rate. As the wire get shorter, such as when cutting the coil, the spring rate increases.”

Note that the ends of the Remington spring are finished. It looks like only one end of the PT&G spring is finished. Finishing the ends at home is not easy.

Just had another idea…double check and thoroughly clean the bolt and firing pin to ensure that there is no crud or debris that would impede its travel, and potentially cause random strikes.

 

[Dusty Stevens]

I need a new firing pin for one of my 40x. Where is the best place go get one and what protrusion should i be getting? I have some ftf and mine is the firing pin giving me issues

 

[1911nut]

I need a new firing pin for one of my 40x. Where is the best place go get one and what protrusion should i be getting? I have some ftf and mine is the firing pin giving me issues

Remington 40x Rimfire Firing Pin - Steel Only - Pacific Tool and Gauge

Remington 40x Rimfire Firing Pin - Steel Only at Pacific Tool and Gauge

pacifictoolandgauge.com

 

[angus]

I need a new firing pin for one of my 40x. Where is the best place go get one and what protrusion should i be getting? I have some ftf and mine is the firing pin giving me issues

I have a 40X that’s chambered in .17WSM. I was experiencing misfires. I installed a 26lb Wollf spring. Problem solved.

 

[scasa]

I have a 40X that’s chambered in .17WSM. I was experiencing misfires. I installed a 26lb Wollf spring. Problem solved.

.17 WSM case is a lot thicker than .22LR and takes a lot more spring

 

[dstoenner]

I would cut 2-1/2 coils off the PT&G spring ( off the unfinished end ), then grind a 1/2 coil off to make it sit flat. That would put the number of coils at 17, the same as the old spring. Unless the profile of the pin tip has been altered, this should put it back close to the day it was new. A larger footprint on the pin, will require a bit more spring to drive it properly.

I agree. This will be step 2. Step one is to put the original back and verify groups. Yeah i thought ptg was cheap not to finish both ends. When i get done with both tests I’ll report back.

david

 

[dstoenner]

Is the diameter of the wire the same on the two springs? I suppose if you had an arbor press and a scale, you could compress each a set and equal amount, and then get a number for fair comparison. Ideally you would compress the springs the same amount as when installed, and then a second time compressed when installed and cocked.

”Cutting coils does increase the spring rate. The only thing that will change will be the length of the wire used to wind the spring. The longer the wire is the lower the spring rate. As the wire get shorter, such as when cutting the coil, the spring rate increases.”

Note that the ends of the Remington spring are finished. It looks like only one end of the PT&G spring is finished. Finishing the ends at home is not easy.

Just had another idea…double check and thoroughly clean the bolt and firing pin to ensure that there is no crud or debris that would impede its travel, and potentially cause random strikes.

I didn’t measure the diameter of both springs. I will when i finish testing step 1.

A coil spring isn't governed by its length but by a constant K which is in lbs per inch. So the value of a spring force is F=-Kx or if there is a precompression, F=-K(X2-x1) Where x2 is the full compression at cocked position to x1 which is the fired position. The constant K is governed by the diameter of the wire and the hardening of that wire. It is from this that you can get an energy equation of what the firing pin impact gives to the case to detonate the primer.

Thinking on this, I believe that my original spring has taken a set. Even in the decocked position the spring is compressed. This spring is almost 60 years old. What took me by surprise is that the extra energy could so disrupt groups like that. I think that is because the firing pin strikes the outside edge and imparts an impulse function to the barrel even before the bullet fires which gets the muzzle moving. Centerfire doesn't have quite the same dynamics because they are central and not off axis and the brass case is more elastic then the barrel so the impact is dampened some.

David

 

[chasespaugh]

How did you remove the cocking piece to replace the spring?

 

[MrG52D]

How did you remove the cocking piece to replace the spring?

You have to have a tool to do this. There is a small cross pin in the cap, the tool let you compress the spring enough to see it.

 

[dstoenner]

You have to have a tool to do this. There is a small cross pin in the cap, the tool let you compress the spring enough to see it.

The same tool that will remove a 700 centerfire tool will remove a 40x tool. I got mine from sinclair now Brownells

David

 

[Baker]

Anybody ever find the 18 pound springs 40x rimfires originally had?
if so where?

 

[ljmontano]

Here is a 5 shot group I shot two days ago at 50 yards with my all original 40X B made in the late 50’s! With two different lots of Center X think I will just leave the original FP spring in. Right?

I

 

[fkimble@charter.net]

The gun was working, you had barrel replaced, gun now not 100%. Sounds like maybe the barrel isn't just right? All springs will take a set. Take a 1911 recoil spring out that's been in there for awhile. Spring will be noticably shorter. Your new spring has 3 more coils than the old spring. I would start taking off a coil at a time and see if accuracy returns and FTF stops.

Frank