How to weaken a coil spring?

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Potashminer

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So had some misfires with a Remington 783 - noticeably light strikes on the unfired primers - 2 rounds out of 33 shots attempted- and those "duds" were re-chambered and re-fired (or tried to) three times. Some rounds were successfully fired after the "duds" - all were same loading batch by me - CCI BR-2 primers. I pulled bullets and dumped powder - both "duds" fired off fine in my Ruger 77 Compact. Advice to me was the firing pin spring in the 783 most likely first thing to replace.

That source suggested to get 24 pound firing pin springs for a Remington 700 Short Action - shorten the spring as needed, and shoot. Of course, Brownells does not list that weight - just the 28 pounds. And, are "Out of Stock" for those. I did find a source in Canada - so 3 x 28 pound Wolff springs being mailed to me.

Advisor now suggests this is too much - threatens the cocking piece / shroud. So, my dilemma - is there a way that I can "weaken" a 28 pound coil spring, down to 24 pounds? How to do that??

I also have Federal GM210M primers and Federal 210 primers on hand - do they have known "softer cups" than CCI BR-2 primers?
 
guntech said:
Try the 28 pound springs and go from there... only 4 pounds difference...
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This.

I'm not seeing four extra pounds force really making a difference unless you were ADDING it (four pounds) to a weaker sprung part.

Cutting coils off just makes it a shorter 28 pound spring. Ideally, what you need is a smaller wire, but if you had the capacity to accurately measure the temperature in an oven, you 'might' be able to temper the heavier spring just a touch and make it lighter, but still a spring. But owning thousands of dollars worth of precision temperature oven, to do that, seems rather poor value!

Oh. I'd look long and hard at how the whole firing assembly fits and works together, before I'd resort to changing out parts, as honestly, it doesn't take a lot of force to whack a primer. But any source of friction inside the bolt can eat a LOT of what is available, and I'd bet, that was where the trouble lay.
 
trevj said:
This.

.....

Oh. I'd look long and hard at how the whole firing assembly fits and works together, before I'd resort to changing out parts, as honestly, it doesn't take a lot of force to whack a primer. But any source of friction inside the bolt can eat a LOT of what is available, and I'd bet, that was where the trouble lay.
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For sure!! To my knowledge, that bolt has never been dismantled, so no telling what grungies, burrs or loose bits might be found in there. I have no illusions, now, about this "bottom of the line" type rifle. The rifle is for my Grandson to use - I never thought there was any sort of issue, when I got it for him to try. He sat out what was to be his first deer season with a broken arm (hockey practice), so pretty much "rarin' to go" this fall...
 
Potashminer said:
For sure!! To my knowledge, that bolt has never been dismantled, so no telling what grungies, burrs or loose bits might be found in there. I have no illusions, now, about this "bottom of the line" type rifle. The rifle is for my Grandson to use - I never thought there was any sort of issue, when I got it for him to try. He sat out what was to be his first deer season with a broken arm (hockey practice), so pretty much "rarin' to go" this fall...
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I hope he has better luck this year. Stuff happens! Or, as a friend of mine pointed out rather politely, "Excrement Eventuates!"

Yeah, I'd be all over the mechanical side, way before i ever bothered to order a spring, as under normal circumstances, the one they bought in bulk at the factory, was seen to be pretty reliable, as far as the folks there had considered.
They don't often consider "all" the various tolerances being a wee bit out though! I think the normal thought is to think that the high ones will cancel the low, and that is not always the case!

In any case, yeah, long before I would change anything, I'd have a really detailed look through the various parts to see where they could be slicked up for essentially no money.
 
I think there was a bad batch of springs in the 783. My older one I had to replace with a 700 spring shortened 1/2". My new model hasn't had an issue yet. But the springs do look noticably different.
 
I would add to the above comments,go ahead and try some loads with federal primers. The scuttlebutt I am aware of has them being softer than most other brands and cci being one of the harder ones. Hope you get it sorted out in time.....catnip
 
Can I disagree about cutting a 28lb spring just makes it a shorter 28lb. Spring rate is actually force / distance so I’m guessing the spring is lbs / in. Cutting the spring shorter would result in the spring rate increasing as you have fewer coils to compress it takes more force to compress the same distance. That said by cutting the spring you would also be decreasing the amount of compression likely resulting and overall decrease in total force. As a side note cutting a spring results in an end that’s no longer flat and can affect function in somethings. I do completely agree that changing wire diameter or spring pitch are the ideal way to adjust spring rate. Depending on how much spring travel you need you can also try shimming your existing spring increasing “preload” vehicles do it all the time.
 
I must admit that I used terms that I read on the Wolff website, and perhaps really do not understand what they mean. For example, they list firing pin springs for Remington 700 Short Action at 24 pounds, 28 pounds and 32 pounds. I do not know if that is as simple as the force needed to full compress the spring to "closed" or what? Since I have three on the way, I have been trying to imagine a jig that I can put a spring into, start adding weight, and see what happens when a "28 pound spring" has to hold 28 pounds of weight, or how closely 3 x 28 pound springs are or are not to each other.

If my assumption is correct - that the weight rating is related to how much weight the spring can carry, then make sense that each coil contributes it share to carry that load - or at least deforms in "springy" response to that weight, but the 28 pounds has to be passing through each coil, all the way along?? One of those things I will want to try to demonstrate to myself.

I am told that the need to shorten the spring for use in the 783 is that the full length 700 part is "too long" and will bind up within the bolt as it is compressed. So, numbers like 1/2" and 3/4" have to be removed to allow it to fit. I do know from messing with other coil springs to try to create a "flat end" - so often that last coil is ground, to increase the contact surface with whatever it is seated against. Again, I will be looking at how the factory terminated the springs, and try to reproduce that.
 
Inserting a shim or block as a "pre-load" - an interesting thought! I will have to see what condition that original spring is in when that firing pin is "cocked" - I presumed it must be near "closed" - coil against coil, so no preload would be possible. But I do not know that - again, to play with and see what I can learn...

In the end, I had been using Federal 210 and 215 primers since the late 1970's - I do not recall performance issues. I bought a case of 1000 CCI BR-2 when I couldn't get Federal Large Rifle 210 - I now have a couple hundred loadings with that primer - most have not been fired, yet - and the Grandson's experience - 33 shots attempted, and two "duds", that later fired in my Ruger 77. New-to-me primers, new-to-us rifle. So something is amiss and I am trying to find it. Many things it "could be" - from a floating grungie within the bolt, a burr, a "weak" spring, unusually "hard" primers, and so on.

Sask. rifle deer season does not start until November. A bit annoyed that our son waited so long - he had fired several hundred rounds in July and August with the rifle and scope combination I had prepared for him - in preparation for his own first deer hunt - 1991? Much better to discover issues on the range, shooting at paper targets - use the things regularly in practice and find the weaknesses there, not out in the field.
 
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The formulae for calculating spring rate indicates that removing coils does reduce it's rate. I don't think preloading will do anything for you.


(G*d4) / (8*n*D3)



[G = Shear modulus, d = wire diameter, n = number of active coils, D = coil diameter]


You can also make coil springs pretty easy from piano wire ....
 
Wolff Gunsprings - from their site - "Load ratings indicated are with the striker (firing pin) in the cocked position and for rifle actions equipped with standard factory parts and designs." - so that "28 pounds" is not really a spring rate rating - more like the spring force available at a particular amount of compression?
 
Yeah it sounds like the 28lbs is just the weight required to compress the spring to a specific length roughly equal to when the gun is cocked. So in theory if you made a jig to hold the spring with a weight on it you could put 28lbs on it and measure length and then just cut coils until you get the same length with 24lbs. This would give you a pseudo 24 lbs spring with a non optimized spring rate and preload. Or just cut the 28lbs so it functions in the gun and if fires cartridges consistently then don’t worry about it, biggest downside to heavier firing springs in a bolt action is the effort to ####. If 4lbs extra force breaks a bolt part then we’ll it’s a poorly made bolt part.
 
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Sean don’t you mean cutting coils will increase spring rate? According to your equation number of active coils is inversely related to spring rate. So but cutting coils you will increase spring rate as nothing else in your equation is altered.
 
"poorly made bolt part" - that has my attention - I am suspecting these Rem 783 were made with components to be "just strong enough" - "on average" - or something like that. USA seems filled with lawyers happy to sue - so, not likely to be made to be "unsafe" - easy enough to blame others for malfunctions, though - not so sure about a defunct, bankrupt like Remington - not really holding my breath - I intend to "make do" with what I have here...
 
Potashminer said:
Wolff Gunsprings - from their site - "Load ratings indicated are with the striker (firing pin) in the cocked position and for rifle actions equipped with standard factory parts and designs." - so that "28 pounds" is not really a spring rate rating - more like the spring force available at a particular amount of compression?
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If you compress the spring while on the firing pin you can measure the force required over a particular distance... in the case of a firing pin you want to measure in the area it is cocked and in the fired position... not an easy task... I have used an old kitchen scale that weighs up to 25 pounds... made a dimple on the center of the top... place the firing pin tip here and compress the shroud assembly until the spring is fully compressed... You can read the scale as you do this... the scale reads to 25 pounds and then overlaps... fairly accurate up to 32 pounds or so.
 
Webley No.5 said:
Sean don’t you mean cutting coils will increase spring rate? According to your equation number of active coils is inversely related to spring rate. So but cutting coils you will increase spring rate as nothing else in your equation is altered.
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In word "no", cutting coils off will reduce spring force every time. Cowboy gun home mechanics have been cutting springs for thousands of main match guns to regulate & tune their Marlin & Ruger "race guns".

Potash , I'm not familiar with the workings of a Rem 783 but if it is a "positive angle" sear latch-up system similar to what Savage uses in their inexpensive Axis, removing spring tension from the firing pin spring will also reduce trigger weight. By Positive angle latch-up I am meaning that the trigger sear actually catches the hook on the firing pin to hold it back and any reduction in firing spring tension also reduces hook engagement tension so for a young lads rifle , I would pay close attention to this.

I will also offer up a suggestion to closely look at the firing pin when you get the bolt apart. I had a P14 one time that was working fine until I purchased a "speed bolt" kit for it from Numerich. When installed I had light primer strikes galore with it...changed the speed bolt spring out with the original and still no joy. Disassembled the bolt again and discovered that the speed bolt firing pin had warped an almost indiscernible amount during heat treatment but enough to cause a slight friction between the firing pin & bolt tube. I knew that if I tried to straighten that pin it would just break (I don't have a 10,000 dollar heat treat oven neither). I just ground a bit off the bulge side of the pin and tried it again, that pin was still in the rifle & working fine when I sold it 20 yrs later.
 
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