Howdy Again
I read the post over at the S&W Forum you referred to. Those guys are talking about revolvers that have been tuned to the Nth degree. They are like race cars compared to a street Chevy. You will notice there are several references to Federal primers. Those guys are mostly using Federal primers because Federals are the lightest brand of primer and require the lightest hit to fire them. Some of those guns will not fire if loaded with ammunition that uses Winchester or CCI primers because they require a harder smack from the firing pin to ignite them. We see this kind of thing all the time in the CAS world. Even though in CAS we shoot single action revolvers, the same holds true. If you tune a gun right at the edge of the envelope it might fire ammo that uses Federal primers, and might not fire ammo that uses Winchester or CCI primers.
Let's talk for a minute about all the things that happen inside a Double Action revolver when you pull the trigger to shoot it in double action mode. Here is one of the photos I posted earlier. Notice I have labelled three sprinigs. You are compressing all those springs when you pull the trigger on any modern S&W double action revolver. Actually, there are a few more springs you are compressing, hidden inside the hammer assembly and at the pawl, but let's just talk about those three for the moment.
Most important is the hammer spring or Main Spring. When you pull the trigger, you are rotating the hammer back, which bends the hammer spring. Obviously if the hammer spring is lighter than usual, it takes less effort to pull back the trigger. There are several ways to lighten the hammer spring, including the incorrect method of backing out the strain screw. The correct way to lighten the hammer spring is to replace it with an aftermarket spring. And you can go further, you can carefully grind the spring down to weaken it further. But if you go too far, lighten it too much, the gun becomes unreliable and will not light off primers reliably. You may wind up with a gun that will only fire Federal primers and will not fire any other brand. Or you may go too far and the gun won't fire anything. But, we have lightened the hammer spring.
The Rebound Slide Spring is also compressed when the trigger is pulled. The trigger strut physically pushes the Rebound Slide backwards, you can see it in the second photo. The Rebound Slide has nothing to do with firing a cartridge, it is what pushes the trigger back forward again when you let go of the trigger. There is a very stiff compression spring inside the Rebound Slide that does the work, you can see it in both photos. So when you pull the trigger, you are fighting both the hammer spring and the rebound slide spring. Replacing and/or lightening the Rebound Slide Spring is common and will not affect whether or not the gun will fire cartridges. But it does affect how smartly the trigger snaps back into position for the next shot. Top shooters like Jerry Miculek actually like a relatively stiff Rebound Slide Spring, because with a spring that is too light, they can actually pull the trigger and let go and be ready for the next shot before the gun can accommodate them. With too light a Rebound Slide Spring they can actually get ahead of the gun.
The third spring I pointed to is the Cylinder Stop spring. The Cylinder Stop is the part that pops up and locks the cylinder in position, ready to fire. When you pull the trigger, there is a nub at the front of the trigger that pulls the Cylinder Stop down, compressing its spring. This is actually a relatively light spring and does not offer much resistance to the trigger.
In this photo you can see how the Hammer Spring and Rebound Slide Spring have been compressed.
What else are we doing when we pull the trigger? We are rotating the cylinder. Even though we are not overcoming a spring to rotate the cylinder, we are physically forcing it to rotate when we pull the trigger. That adds to perceived trigger pull.
And we haven't even talked about friction yet. Those Race Guns in that post on the S&W Forum have had extra work done to eliminate as much friction as possible in the mechanism. Merely putting in light springs is self defeating if one does not also eliminate excess friction. By carefully polishing selected surfaces of the parts, a skilled gunsmith will reduce the internal friction of the parts so the gun will reliably function and fire ammunition with lighter springs. Without polishing the parts, we get a gun with a very light trigger pull that will not reliably fire standard ammunition.
By the way, the Original Poster in that forum is dreaming when he talks about two to four pound trigger pulls on a modern S&W revolver. Just ain't gonna happen and have a reliable gun. I don't care what brand of primers he uses.
OK, I tested the trigger pull on a few more of the Smiths in my collection, using my trusty digital fishing scale. Note: these are all stock guns, none of them has been turned into a race gun.
38 M&P, 1930s vintage - 12 pounds
38 M&P, 1940s vintage - 10 pounds
Model 617 - 12 pounds
Model 65 - 12 pounds
Model 624 - 10 pounds
Model 1926 (made in 1929) 10 pounds
K-22 1930s vintage -12 pounds
Model 14-3 made in 1975 11 pounds
Model 17-3 made in 1975 11 pounds
Triple Lock Target Model made in 1908 11 pounds
Bekeart 22 Target Model from the 1940s - 13 pounds.
Note that the Model 14, 17, K-22, Triple Lock, and Bekeart were the premier target pistols of their day.
Is a Safety device needed on any of these guns? Absolutely not. No way they are going to discharge unless somebody pulls the trigger on purpose.
How about the 4 1/2 pound guns over at the S&W Forum? Of course not. Those are race guns. Nobody is going to be messing around with them in the woods. Anybody who shoots those guns knows what he is doing and knows the safety device is between his ears.
