FP spring weight affecting accuracy

[Gil P.]

What are your experiences with firing pin spring weight affecting your accuracy and SDs?

I just ordered a light 22# spring to replace the heavy 26# spring in my BAT TR. BAT says it could negatively affect accuracy, but to give it a try and see what happens.

Why would changing to a lighter spring affect accuracy? Inconsistent ignition?

The main reason I want to try the light spring is to make the bolt throw lighter.

 

[CharlieNC]

I don't know an answer regarding the best spring force, but I know it is a major factor. Shooting 200yd, I was experiencing a high percentage of fail to fire issues. A few minutes later after changing the spring on the spot, the point of impact went up by an inch or so. Ignition!

 

[WyleWD]

Why would changing to a lighter spring affect accuracy? Inconsistent ignition?

When the 24# springs I use get weak, it shows up on the target and kinda sneaks up on me and I get fliers usually. Just replaced one that was only 6 months old and it had lost almost 5# of compression. JME. WD

 

[Gil P.]

I don't know an answer regarding the best spring force, but I know it is a major factor. Shooting 200yd, I was experiencing a high percentage of fail to fire issues. A few minutes later after changing the spring on the spot, the point of impact went up by an inch or so. Ignition!

Wow that's a huge difference! what weight did you start with? Did you replace it with the same weight or higher weight spring?

 

[Gil P.]

When the 24# springs I use get weak, it shows up on the target and kinda sneaks up on me and I get fliers usually. Just replaced one that was only 6 months old and it had lost almost 5# of compression. JME. WD

That's good information as far as maintaining springs.

 

[CharlieNC]

Wow that's a huge difference! what weight did you start with? Did you replace it with the same weight or higher weight spring?

I don't know the weight, just replacing factory with factory. But the old one was clearly weak due to the fail to fires, which prompted me to change it.

 

[rogina]

What are your experiences with firing pin spring weight affecting your accuracy and SDs?

I just ordered a light 22# spring to replace the heavy 26# spring in my BAT TR. BAT says it could negatively affect accuracy, but to give it a try and see what happens.

Why would changing to a lighter spring affect accuracy? Inconsistent ignition?

The main reason I want to try the light spring is to make the bolt throw lighter.

It will change the vibration, which will change the harmonics.

 

[gunsandgunsmithing]

It will change the vibration, which will change the harmonics.

I disagree, to a point but it's an important one. The barrel, rifle...whole contraption, will vibrate at the same frequency but the amplitude will change if hit with a bigger hammer, ie, a heavier spring. Frequency and amplitude are two separate things, not directly affected by one another.

 

[Will Henry]

Must have been about twenty years ago, I was visiting with a maker of ultra-high quality falling block and Mauser sporting rifles. He told me, if he tested one of his rifles and it produced vertical groups, his first move was to replace the striker spring. He said this seldom failed to produce the desired effect. About this time, I had a .308 rifle I had built on a pre-war Model 70 action. Shooting Lake City match ammunition, it produced 300 meter groups which were about 3 inches wide but six inches tall. I put in a new 26# Wolff spring and my vertical dispersion dropped to about 3.5 inches. Since then, spring condition is something I have paid more attention to. I also learned that even makers who are not precision oriented builders have knowledge to share as well. This particular gunmaker has been at it for more than sixty years and has produced work which is unbelievably well done. WH

 

[JohnKielly]

Consistent ignition. It's why we uniform primer pockets, seat carefully by feel or measurement & for that matter, select a particular primer. Why wouldn't a fingers crossed just good enough light firing spring be a risk?

 

[jackieschmidt]

A number of years ago, a good friend bought a new Farley action and had a LV Bench Rest Rifle built on it.

The first day he had it at the range, we all marveled at how easy the bolt lifted and how slick it was.

The rifle would not shoot. .350 groups were the norm.

I took a good look and noticed it only had around .170 inch firing pin fall. the spring felt like around 18 lbs.

We took it to my shop where I offset bushed the trigger hanger pin holes to get .220 inch firing pin travel. I then made a spacer to bush the spring, giving it 24 lbs of static pressure.

When we got back to the range, the first group was about .150.

I follow Kelbley’s recommendations on firing pin travel and spring pressure. They got it right.

Of course, the bolt was a little hard to open. We traded good shooting rifle for real easy bolt lift.

 

[JFrank]

@jackieschmidt
What can I do to have both easy bolt manipulation and good accuracy ?

 

[dkhunt14]

A number of years ago, a good friend bought a new Farley action and had a LV Bench Rest Rifle built on it.

The first day he had it at the range, we all marveled at how easy the bolt lifted and how slick it was.

The rifle would not shoot. .350 groups were the norm.

I took a good look and noticed it only had around .170 inch firing pin fall. the spring felt like around 18 lbs.

We took it to my shop where I offset bushed the trigger hanger pin holes to get .220 inch firing pin travel. I then made a spacer to bush the spring, giving it 24 lbs of static pressure.

When we got back to the range, the first group was about .150.

I follow Kelbley’s recommendations on firing pin travel and spring pressure. They got it right.

Of course, the bolt was a little hard to open. We traded good shooting rifle for real easy bolt lift.

I am sure that .050 pin fall helped alot. I believe pin fall is as important as the pounds of a spring. I have found out 18 pounds is about the minimum of where things Start to go south. I replace when it gets down to that. Matt

 

[Rat Rifle]

I’m going to have to seriously look at this.

 

[wkdickinson]

I am sure that .050 pin fall helped alot. I believe pin fall is as important as the pounds of a spring. I have found out 18 pounds is about the minimum of where things Start to go south. I replace when it gets down to that. Matt

In a non-labratory setting, how do you measure the force of a striker spring?

 

[243winxb]

http://benchrest.com/showthread.php?102626-Kelbly-Actions-What-not-to-do-to-improve-accuracy

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jamesakelbly- The standard for Kelbly actions is 22 – 24 pound springs

Would a heavy spring produce shoulder setback, on pin strike, annealed soft brass?

Edit/add -When my 223 had a bad primer, set back was .006" Savage Axis, the type of extractor may make a difference? Not a Benchrest rifle.

 

[Will Henry]

I have never been able to measure any set back, with any cartridge, resulting from the firing pin strike. The primer deforms long before any set back can occur. I have also substituted nylon and solid brass for the primer and still, no set back. WH

 

[rogina]

A number of years ago, a good friend bought a new Farley action and had a LV Bench Rest Rifle built on it.

The first day he had it at the range, we all marveled at how easy the bolt lifted and how slick it was.

The rifle would not shoot. .350 groups were the norm.

I took a good look and noticed it only had around .170 inch firing pin fall. the spring felt like around 18 lbs.

We took it to my shop where I offset bushed the trigger hanger pin holes to get .220 inch firing pin travel. I then made a spacer to bush the spring, giving it 24 lbs of static pressure.

When we got back to the range, the first group was about .150.

I follow Kelbley’s recommendations on firing pin travel and spring pressure. They got it right.

Of course, the bolt was a little hard to open. We traded good shooting rifle for real easy bolt lift.

I had the same thing happen with my Farley. They put in a new trigger hanger, increased the fptravel and a new spring and it went to shooting.

 

[dkhunt14]

In a non-labratory setting, how do you measure the force of a striker spring?

I made an aluminum piece that the fire control sits in and you press down on a scale. Matt

 

[gunsandgunsmithing]

I made an aluminum piece that the fire control sits in and you press down on a scale. Matt

I'll add to that, a mill or even a drill press helps to compress it to the "cocked height."