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American Handgunner May/June 2011 - Page 38
PISTOLSMITHING Alex Hamilton THE INSIDE SCOOP ON PISTOLSMITHING TECHNIQUES Drop-in SpringS? i f I had to pick two subjects that come up in gunsmith’s shops I would have to say “springs” and “sights” are at the top of the list. The subject of springs comes up constantly and there are many pseudo gunsmiths who don’t have a clue as to the relationship of the spring to the geometry of a revolver or pistol. In order for the geometry to work as designed the spring (stored energy) must be of the proper weight, diameter and length. There is a lot more involved than just forcing the hammer forward with enough energy for the firing pin to crush the primer. When shooters buy springs they’re usually trying to get a lighter double action or single action pull, but without understanding the physics involved they get into trouble quickly. Aftermarket mainsprings, the flat spring that operates the hammer in a S&W, for instance, is a real bugger and if too light will not propel the hammer forward with enough force to bust a cap. I rarely, if ever replace the factory mainspring in a S&W or any other double action revolver unless it’s a coil Here’s the working relationship of the hammer to the rebound block and the rebound block to the trigger. spring with excessive force like you find in Ruger revolvers. On occasion I will bend the tip of the flat spring back a little and back off the strain screw located at the bottom of the grip a quarter of a turn for a little better feel. If you run into problems with unreliability the fix is quick by turning the strain screw back to the factory setting. You can play around with this without doing any permanent damage. A Wolff spring pack with the 12-pound rebound spring most commonly used for lighter double-action trigger pulls. J-Frames he small S&W J-frame revolvers are real problems when changing out the coil mainspring. The geometry in these excellent revolvers is so tight and the hammers so light and small they need a strong spring to drive the firing pin into and crush the primer. I usually change the J-frame mainspring to an eight pound, but when that is done you must also do other things such as hone and polish hammer and trigger contact points and other action work to make it smooth and reliable. The J-frame revolvers and all revolvers of that size should have a complete action job performed by a competent gunsmith. Simply changing out springs will get you into trouble fast. Your life, the life of that gal you sleep with, and the lives of those kiddies down the hall just ain’t worth it. The most critical of all the springs in revolvers and pistols is the trigger return spring. In S&W double-action revolvers that spring resides in the rebound block located directly behind the trigger and below the hammer as shown in the photograph. The rebound block and spring has another critical function other than resetting the trigger for the next shot. The rebound has a square bump on top called the “seat,” These are the which when moving forward cams three springs in another square seat on the bottom a S&W revolver, of the hammer. The rebound seat with the large coil spring cams against the hammer seat to being critical to move the hammer back and out of proper function. the way so the cylinder will turn The flat spring for the next shot. is the main T The energy for all this motion is controlled by the rebound spring. If the rebound spring is too light it cannot perform this important duty and the trigger sticks to the rear. When I do an action job, I polish the inside of the rebound block and change the rebound spring to a 12-pound Wolff. However, in most cases the 12-pound spring is not enough to overcome the pressure of the hammer spring and the rough surface of the rebound seat and hammer seat. Both seats must be properly beveled and polished to a mirror finish to aid this critical function. A final thing to remember when changing a factory spring to a lighter one in order to achieve a lighter action is you are also slowing down “lock time” which is detrimental to accuracy. I have seen single actions with hammer springs so light the hammer appears to be falling in slow motion. The huge, heavy hammer will still bust a cap, but when lock time is so slow you can actually see it, the revolver or pistol will move before the cartridge detonates and that ain’t good for accuracy. The bullet impact will usually end up low and to the left of the desired impact point. Lock Time * spring. For more info: Wolff Springs, (800) 545-0077, www.americanhandgunner.com/wolff-springs WWW.AMERICANHANDGUNNER.COM • MAY/JUNE 2011 38