Tips on grinding down the S&W leaf mainspring?

Z

ZWolfgang

New member
I've read that using a bench grinder is a good way to lighten the leaf mainspring on a S&W K/L frame gun... trimming the edges, not the flat part.

Are there any more detailed tricks/tips I should know before I lay my leaf spring up against the grinder? Many thanks in advance...
 
Sounds like an experiment

Well, I hope you have an extra spring just in case. But if you bought one, you could have bought a lighter spring from an aftermarket supplier. I guess the thing to do when grinding a spring is to never get it too hot or it will lose it's temper and springiness. Maybe a little bit at a time with care? Did you try just turning out the mainspring retaining screw a turn or two? You can reduce the spring force on the hammer by doing that, up to a point. Too much out and you will have a too light force which might cause a malfunction and misfires. Also, the spring can straighten out too much and cause knuckling where it will not cock. If the trigger pull is then lighter, make sure that it is not so light that you can thumb push on the hammer and have it come out of cocked position. A lighter trigger return coilspring can also reduce trigger pull, but it must be strong enough to reliably return the trigger. I have seen the mainsprings on competition single action Colt types ground to be narrower, not thinner, in dimensions. You can even buy them cut like that for the SA revs., but real care still needs to be taken for safety and sure-fire action. You can get a reduced power S&W spring from Brownells, or others, that is made by experts to reduce DA pull. Good luck
 
That is a pld myth. Buy a good spring kit from C&S, Wolff or other manufacturer. They have a ridge that lightens the felt resistance, a lighter rebound trigger reset spring and they reduce the felt tension. The better ones also include a forged and extended firing pin for frame mounted newer S&Ws. 100% ignition. When the gunsmith has your revolver disassembled, ask him to stone and polish the internals also.
 
There are several things that can be done to lighten the S&W trigger pull. But never, EVER mess with the mainspring. Tampering with the mainspring or replacing it with lighter aftermarket springs is a sure recipe for misfires. Same goes for messing with the strain screw. I've bought several used S&Ws over the years only to discover they had a problem with misfires. In every case the cause turned out to be either a tampered with mainspring or an aftermarket mainspring. The only truely reliable mainspring for a S&W revolver is the factory original part.
 
Some old guy name of Skeeter Skelton ground down a lot of mainsprings. See if you can find somebody with a collection of Shooting Times, there was an article he did in one with a good picture of the profile he used.
 
I think I'll just go for a lower power Wolff mainspring... all of my Smiths have hammer-mounted firing pins which I understand are less prone to light primer strikes after installing a lighter mainspring than the frame mounted firing pin models are. Another nice thing about having an "older" gun! ;)
 
Something else to bear in mind:

It was a few decades ago when the Late, Great, Skeeter Skelton wrote of mainspring reconfiguration as part of revolver tuning. This was before one could easily obtain the excellent Wolff Springs assortment of main springs. "Back in the day," S&W offered exactly ONE mainspring for the Hand Ejector series, so possibilities were rather limited.

I recall a Skelton article in which he illustrated modification of the Colt DA V-type mainspring, too. Many home workshop tinkerers ruined these relatively expensive springs in this manner. (Hey, if a little bending is good, I'll make mine BETTER!) Some wondered if ol' Skeet wasn't trying to sell parts for Colt.

As I recall, the articles always included the warning not to begin such a project unless you had at least one stock spring in reserve . . . .

If you DO perform such home modifications, PLEASE do not rely on it for personal defense until you have throughly tested it. This includes a range trip, shooting ANY ammo you might use in the revolver. (Your sweet new M65??) Primers on some magnum ammo are a lot harder that most .38 Spls. A hammer fall that ignites .38 +Ps reliably might or might not serve to light up a magnum.

Best,
Johnny
 
I test any gun with reduced mainspring, whether altered or store bought, with handloads and CCI primers. Their primers are the hardest on the market and not likely as well seated as a factory primer in vigin brass. If those shoot, I have never had a failure to ignite another brand of primer or a name brand factory load.

I have an old Python with action job by the Colt Custom Shop. It has a "raftered" V spring done at the factory by or under the supervision of Tedford himself and will not reliably pop any but Federal primers. Factory made is not a guarantee of absolute reliability.

Shooters and writers seem less adventurous these days. Too many lawyers and too many people willing to jump in with both feet without studying the situation.
 
A lightened mainspring ( even with the aftermarket kits) can make your gun sensitive to primer types. Consider this if it's a potection gun. You can also just turn the adjustment screw out 1/2 turn or so to give you some relief. ( Nice part about this is that it's totally and instantly reversable. )
 
"A lightened mainspring ( even with the aftermarket kits) can make your gun sensitive to primer types. Consider this if it's a potection gun. You can also just turn the adjustment screw out 1/2 turn or so to give you some relief. ( Nice part about this is that it's totally and instantly reversable. )"

Not advisable! That screw is meant to be all the way tight against the grip frame. That screw keeps necessary tension and arch on the mainspring. If you loosen it, it will work itself even more loose in a very short time, taking reliability with it.
 
Grinding revisited

I did not really want to endorse grinding the spring at all in the posting above, but I was gonna give the guy the benefit of the doubt, not knowing where he got his info, his experience, etc. I had tried one of the ridged springs on my 66 and did not like the results at all. Way too light. Finally I just picked thru my selection of factory springs and found one that lightened the trigger pull appreciably from the original, without making it super light and maintaining reliability. Then I selected a Brownells rebound spring a little lighter but with good return force. Smoothed up the internals and it is super good for me without the hazards of messing with the sear engagement and the like. I have ground mainsprings on Italian blackpowder revs, as most are so heavy they smash the heck out of the caps and even bash the nipples a bit. Alot more force than is needed to bust a modern cap and accelerates wear on these soft steel replica guns. But there is no aftermarket spring for an 1858 Remington.
 
Lightening S&W mainsprings is easy. A regular bench grinder will work. So will a Dremel. I assume first of all you know how to remove the leaf spring. Start on the right side of the spring. Grind off about 1/2 of the way the full length. Then start grinding on the left side and grind off the other 1/2. Throw away what is left. Then go to http://www.gunsprings.com/ and order a full set of replacement springs.
Hint: You can save yourself some time if you order the replacement a few days before you start grinding.
 
I ground a couple of 66 mainsprings for learning and found the ribbed Wolff springs give a lighter and smoother pull for the same striking force. If you want to grind a spring, I use a large flat file. Put the spring in a small vise and work one edge starting about 1/2" above where the strain screw hits it. Do both side evenly and keep cutting the sides in until it lightens as far as you want. It's way more trouble than it's worth when you can get a better spring from Wolff for maybe $12.
 
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