How To Detect And Correct Hammer Drag
September 23, 2010
If you look carefully, you'll see drag marks on the hammer. Generally, hammer drag can be easily corrected.
I love revolvers. I guess it may be my age, or then again, it could be the problems I've seen over the years with auto pistols. Sure, you can't beat a semiautomatic in a combat situation, but at my age, I doubt seriously I'll ever again be in a place where that's very likely. Nope, revolvers are more than adequate for my needs and the needs of most folks. Of course, I still own and shoot a bunch of auto pistols, but they just don't have the same appeal to me as a good revolver.
That's not to say revolvers are the ultimate handguns and are absolutely reliable and trouble free. Heck no! I can't imagine anyone who's worked as a gunsmith would ever say that about any firearm. After all, a revolver is just a machine--a mechanical tool--and it will wear out and break given enough time and use. But like me, the average gun owner will seldom wear out a new revolver in his lifetime. Generally, it'll take several life times.
For many of us, that's the catch. Most gun owners I know who have multiple handguns have more that were previously owned than they do new ones. Like mine, some of those revolvers go back quite a few years and probably have been owned and fired by a lot of folks. The natural consequences of age, use, and wear will often show up on these older handguns.
One of the most noticeable points of wear relates to the hammer. When a revolver cycles--either double- or single-action--the hammer must move through an arc as it pivots on a pin inside the frame. Generally, the friction between the hammer and the pin is absolutely minimal and has very little significant effect on the operation of the firearm.
On the other hand, there can be contact between the side of the hammer and the interior of the frame. If there is, this can lead to serious consequences. Primarily, it can slow the hammer down as it falls forward when it is released from the trigger sear. If there is enough pressure between the frame and the hammer, it can actually cause a light strike on the primer and lead to a misfire.
Contact with the frame can also be an indication of misalignment of the hammer with the firing-pin hole. On revolvers with firing pins attached to the hammer, this may lead to misfires as well as excessive wear or damage to the firing pin. Over time, it can enlarge the firing-pin hole in the frame. If this condition persists, the firing-pin hole can get so large that the primer will back out into it and lock up the gun when it's fired.
In the double-action mode where the hammer is cammed back as the trigger is squeezed, hammer drag can increase the weight of the trigger pull. Double-action shooting is difficult at best under normal conditions, and significant hammer drag can make it just that much harder.
Another often-overlooked aspect of hammer drag is the effect it has on consistent trigger pull. Keep in mind that if the hammer is moving side to side on its pivot pin, it's changing its position or location relative to the trigger sear. The hammer and trigger are not coming together at exactly the same point each and every time. When this happens, you'll have variations in trigger-pull weight. I've seen some revolvers where this was very noticeable.
Installing a trigger shim on the left side of this trigger eliminated the trigger drag.
Fortunately, hammer drag is normally easy to spot. In most cases, you'll see wear streaks on the side of the hammer. Generally, it'll just be on one side, but if the hammer is moving back and forth on the pivot pin, you can sometimes find wear on both sides. Of course, these wear streaks are easiest to see on a blued or casehardened hammer. If a hammer has been polished bright or is nickel-plated, these marks can be harder to see. Also, drag marks are not necessarily just found on visible portions of the hammer. You can also have drag marks on the lower portion of the hammer that's covered by the frame. The only way to thoroughly check for drag is to disassemble the handgun.
Smith & Wessons, like many better-quality revolvers, have a small, raised boss around the base of the pivot pin. There's also a similar boss around the seating hole for the pivot pin on the inside of the sideplate. The function of this boss is to properly position the hammer and keep it from contacting the frame. These bosses can wear over time. I've also seen more than one revolver where the owner has inadvertently stoned away or lowered the height of these important bosses in an effort to smooth and slick up the action. No matter how it happens, the results will be the same; the hammer will move side to side on the pivot pin and contact the inside of the frame.
Correcting Hammer Drag
Fortunately, that problem can be corrected easily and quickly thanks to the efforts of one of the finest pistolsmiths in the country, Ron Power. He offers sideplate shims that can be used on any K-, L-, N-, and J-Frame S&W. These shims are made of 302 stainless steel, are only .002 inch thick, and are about .365 inch in diameter. They're specifically designed to replace worn or damaged hammer-pin bosses and to help position the hammer on the pivot pin in the frame. The end result is less friction and a smoother, lighter action.
The shims are available from gunsmith supply houses such as MidwayUSA and Brownells as well as directly from Power Custom. Use of the shims is simple and straight forward.
First, carefully examine the gun and determine if there is drag on one or both sides of the hammer. Let's suppose there's drag on just the left side. Disassemble the revolver and lift out the hammer. Then place one shim over the hammer pivot pin. Reassemble and check for contact on the side of the hammer. If necessary, coat the side of the hammer with machinist layout fluid so that even the slightest contact will show up. Cycle the revolver, and if there is still contact, take the gun apart and add shims until the hammer moves freely.
If there's contact on the right side of the hammer, you don't even need to remove the hammer from the gun. Just place a shim over the pin as it projects from the right side of the hammer, replace the sideplate, and check for contact.
One note of caution: Don't stack up so many shims that they press against the sides of the hammer when the sideplate screws are secured. This could create hammer drag to the point that the hammer won't even move.
Hammer shims by Power Custom are designed to eliminate hammer drag quickly and easily, and according to Reid, they usually work like a charm.
Check The Trigger
Once any hammer drag has been eliminated, you also need to look at the trigger as well. Just like the hammer, the trigger pivots around a pin. Also just like the hammer, it's subject to drag on the inside of the frame. As with the hammer, indications of contact with the frame will normally show up as wear marks on one or both sides of the trigger.
Just as with hammer drag, trigger drag can cause a number of potentially serious problems. First, if the trigger is moving back and forth or side to side on the pivot pin, this can--and almost always will--have an effect on the consistency and quality of the trigger pull. The contact points on the mating surfaces between the trigger and hammer will vary each time the gun is fired. Also, I have seen revolvers in which drag prevented the trigger from automatically moving completely forward after the gun had been fired. This has usually occurred when the rebound spring was weak, and the trigger would literally stick to the rear.
Here again, Power offers shims to correct this condition. As with the hammer pivot-pin shims, the trigger shims are available in packs of 10 for K-, L-, and N-Frame revolvers. The individual shims are only .002 inch thick and about .245 inch in diameter. They're made of the same material as the hammer shims. Due to the design of Smith & Wesson revolvers, the trigger pivot-pin shims must be significantly smaller in diameter, and in case you're wondering, you can't substitute the hammer shims for the trigger or vise versa. Installation and use of the trigger shims is the same as for the hammer shims.
As I said before, this is normally an easy fix and a great way to make good revolvers even better.
Until next time, good luck and good gunsmithing!