Reducing leaf spring tension

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Metman2

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I have an Italian replica .50cal trade rifle with a very strong mainspring. Trigger weight is very high, off the scale, so it's in excess of 15 lbs. I've read in other forums about reducing tension of the mainspring by grinding it to reduce its width. You're supposed to grind along the length of the spring and not across so that you don't introduce any spots where it might start to crack. Grinding too quickly overheats it which is to be avoided as well.

Has anyone here at CGN done this? It sounds straightforward but I'm cautious and I don't have a spare mainspring handy in case of trouble.
 
The mainspring is unlikely to be the problem; it is far more likely the sear notch on the tumbler and perhaps to a limited extent the tension of the sear spring. I would suggest having a knowledgeable person make the adjustments for you

cheers mooncoon
 
Another trick to try is to put a little leather washer under the spring where the screw goes through. If you can do such a thing with your setup. It's reversible if it doesn't work, and cheap if it does.
It lessens the angle of the spring a little bit and makes the tension a bit lighter.
 
Metman2 said:
I have an Italian replica .50cal trade rifle with a very strong mainspring. Trigger weight is very high, off the scale, so it's in excess of 15 lbs. I've read in other forums about reducing tension of the mainspring by grinding it to reduce its width. You're supposed to grind along the length of the spring and not across so that you don't introduce any spots where it might start to crack. Grinding too quickly overheats it which is to be avoided as well.

Has anyone here at CGN done this? It sounds straightforward but I'm cautious and I don't have a spare mainspring handy in case of trouble.
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this is what I have always done to leaf / flat springs , reduce the width . most of the time I just use a file and a set of calipers to measure before and after and to keep things the same dimension , just narrower .

file , fit to gun and try ..... then if not happy , file ... then fit to gun and try .....repeat until your happy with it .

I don't like grinding as it is too easy to over heat the spring and ruin it .

before you play , make sure you have extra springs . if you have no extra's leave the original alone and build yourself a spring and play with that .

when I'm finally done with the spring and happy with it i'll "polish " it with 600 grit wet / dry sandpaper and oil .... or something similar .
 
I'm more a fan of reducing the thickness instead of the width. That way the spring maintains it's sideways stiffness. Also by reducing the thickness the spring puts less stress on the remaining metal when the hammer is cocked. So it's likely that the spring will resist breaking at some future point if it was at all close to the edge of having an issue.
 
Perhaps I should repeat myself; the problem is not the mainspring tension, it is the angle of engagement between the sear and the tumbler. If the notch is angled to much towards the sear, it becomes increasingly difficult to release because in effect, the sear has to push the tumbler forward for the sear / tumbler to release. If it is angled too much forward and away from the sear, the sear will not hold. Also keep in mind that the tumbler is probably mild steel case hardened. That means that you may have to recase the notch if you stone too much off of it. Buy a spare tumbler first then work on the one that you have. One final time; a strong mainspring does not mean a heavy trigger pull if the notch is angled correctly

cheers mooncoon
 
mooncoon said:
Perhaps I should repeat myself; the problem is not the mainspring tension, it is the angle of engagement between the sear and the tumbler. If the notch is angled to much towards the sear, it becomes increasingly difficult to release because in effect, the sear has to push the tumbler forward for the sear / tumbler to release. If it is angled too much forward and away from the sear, the sear will not hold. Also keep in mind that the tumbler is probably mild steel case hardened. That means that you may have to recase the notch if you stone too much off of it. Buy a spare tumbler first then work on the one that you have. One final time; a strong mainspring does not mean a heavy trigger pull if the notch is angled correctly

cheers mooncoon
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Makes sense to me. I have some experience in another context, having reduced my 1911 trigger pull from 12 lb (!) down to a respectable 4 lbs. It was only partly alleviated by a reduction in the mainspring tension - probably more trigger weight reduction came from just polishing the sear/trigger contacts and also very light stoning of the full-#### notch. That time, I had spare parts to cover any booboos. In this case I will have to wait to get some spares for the same reason.
 
Bertram Brown's 1859 Companion to New Rifle Musket states:
trigger 7 to 8 pounds
lock 13 to 14 pounds
main spring at the half #### 13 to 14 pounds

I had to completely redo my Baker musket lock as all pull weights were stupidly high.
I took the lock completely apart and gave everything a light sanding with 800 grit Used my finger to gauge smoothness. Then a green jeweler's rouge polish. That dropped my trigger pull from 12 to 5 pounds.
I also made sure that the various parts mated well. Sear to tumbler, tumbler to main spring, etc. For example the main spring was not flat on the tumbler. A couple of careful strokes with the file file fixed that.

Working on the tumbler notch scared the hell out of me as even a slight miscalculation with the notch angle can produce a hair trigger.
I filed (skinnied not thinned) the main spring to get the hammer half to full #### pull from 23 pounds down to 12 pounds and that did NOT make an appreciable difference to the trigger pull.
cheers, Ted
 
Listen to Mooncoon and Tedscanoe: sear tumbler engagement angle is most likely to be the problem. The angle of engagement for the tumbler notch face and sear contact point should be an extension of a straight line from the tumbler centre of rotation. If your trade gun is flintlock, then reducing the mainspring will also be likely to reduce the sparking power of the lock. Another way to reduce the weight of trigger pull is to adjust the trigger geometry so the distance between the trigger pivot point and where the trigger blade presses against the sear arm is about 1/4". That will improve the trigger leverage against the sear resistance and reduce the effective weight of the trigger pull for your finger
 
Anyone have any idea how to make the mainspring stronger??
My Snider's hammer blow is often too light to ignite the primer first time - even though I'd moved to pistol primers.
Have to recock about 80% of the time.
Done wonders to prevent flinching, mind.....
 
Steyr1 said:
Anyone have any idea how to make the mainspring stronger??
My Snider's hammer blow is often too light to ignite the primer first time - even though I'd moved to pistol primers.
Have to recock about 80% of the time....
Click to expand...

yes and no; you can increase the tension by increasing the preload meaning that if you heat the spring red hot and increase the opening of the V, the amount of spring compression when the hammer is down, is increased. The no part is that when working with an unknown spring material, there is a high risk of the spring breaking after it has been retempered. I make my springs out of drill rod because for me it is predictable and dependable. After hardening, I draw the temper in molten lead to 720 - 740 F using a high temperature thermometer
The only other alternative that I can think of is to put a small piece of wood or stiff leather in the angle of the V which shortens the length of the moving arm of the spring and makes it a bit stiffer

cheers mooncoon
 
Thanks,guys.
I guess I'll try the leather trick first, then the washer, if necessary.
(Either way, it ain't gonna happen 'till spring)
 
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