"Unlocking reversing cylinder syndrome"???

In a post from 2008 Sledgehammer referred to "unlocking reversing cylinder syndrome" when recommending that the person thinking about getting a Model 629-1 .44 check for that condition by test firing the revolver with 240 gr magnum ammo. What exactly is "unlocking reversing cylinder syndrome"?

Welcome to the forum, JEBevis. In over 50 years of shooting revolvers, I have never heard of this "syndrome". I'm hangin' around to get the explanation myself....

Well, it kindof looks like this:


I've only had it happen when shooting warmish 270gr 44mag loads DA. There is a video on youtube clearly showing the hammer bounce that is responsible for the unlocking. BTW, I can prevent it from happening with my 329pd by using a very firm grip. It hasn't ever affected operation for me, so I don't get excited about it.

dla - would this hammer bounce cause the hammer to lock in the rest position and not allow me to pull back on the hammer to the cocked position in preparation to fire the next round? Because that's what happened to me today at the range. I had to open the cylinder and close it in order to be able to cock the hammer. Granted, it was my first time at the range firing my newly acquired (but "used") model 629-1, and maybe I wasn't gripping as tightly as I needed to. I'll see what happens on my next trip to range. Thanks for the reply.

This became an issue back in the '80's when shooters began shooting a large number of 300 grain bullets at magnum velocities. Sometimes the recoil would cause the cylinder stop to bounce and unlock the cylinder and it would rotate backwards. Smith addressed this in the early '90's with their enhanced models. The cylinder stop was elongated, and there were some internal engineering changes to reduce the possiblity of this occurring. It does not happen as often with use of 240 grain or less bullets.

Nightowl said:

This became an issue back in the '80's when shooters began shooting a large number of 300 grain bullets at magnum velocities. Sometimes the recoil would cause the cylinder stop to bounce and unlock the cylinder and it would rotate backwards. Smith addressed this in the early '90's with their enhanced models. The cylinder stop was elongated, and there were some internal engineering changes to reduce the possiblity of this occurring. It does not happen as often with use of 240 grain or less bullets.

Click to expand...

Nightowl, that's a very concise and well stated explanation. Thanks. This old geezer learned something new. What a GREAT way to start the new year......

Thanks Nightowl, for the explanation! Hopefully this is not a common occurrence with my new toy. If it does keep happening is there any solution to my problem?

JEBevis said:

Thanks Nightowl, for the explanation! Hopefully this is not a common occurrence with my new toy. If it does keep happening is there any solution to my problem?

Click to expand...

Remember though that the cylinder stop can't move unless the hammer bounces back.

Common occurrence with early .500s and right handed shooters, using heavy ammo (500-725 grain bullets). Cylinder stop retracts under recoil, unlocking the cylinder. The gun recoils up and twists counterclockwise about 65-80 degrees, and the cylinder "stays still" while the frame rotates around it. The chamber that just fired ends up in the one o'clock position, leading some people to say it "reverse" rotated.

The factory fitted a heavier cylinder stop spring to fix this.

Grip strength and palm fat are factors too.

That very thing happened to my friend's 386 and I think a 3 1/2" 27-8. He got rid of both guns.

Are we mixing "doubling" in with this? Post #3 seems to point at a mechanical failure in older models with the smaller stop notches while some of this sounds more like the trigger finger reflex on the trigger while the gun is under recoil. Or are the two interconnected in a way I'm not understanding???

Had this problem with my pre-owned 29-2 firing reloads with 240 grain cast bullets. This gun had been abused and was returned to the factory to have a new cylinder installed. The original cylinder, according to the factory, had been "blown." Asked that that the revolver be enhanced as much as possible. On return there was no problem with the cylinder unlocking. Most noticeably,The spring for the cylinder release was significantly stronger.

I had that problem with a Model 25.

I plan to go to the range on Friday and shoot some 240 gr American Eagle .44's (ones i had the problem with) and some 180 gr Remington .44's. I'll let you all know what happens.

I'd like to expand a bit on what already has been a very informative discussion. The product improvements that S&W did to the 44 Magnum (most specifically) go well beyond those needed to correct what has been called cylinder stop (or bolt) bounce in this thread. The most noticeable external change to correct this are the elongated cylinder stop notches. What is not so well know are the rather extensive internal modifications to correct this. In part they include the addition of an additional lever that when the gun is cocked in SA or reaches hammer release in DA, bears against the cylinder stop (or bolt) holding it in a locked position. I have a Model 629-4 Classic and my gunsmith showed the new mechanism to me when last we cleaned and lubed the gun. Interestingly, my 625 Classic in 45 Colt has all the same machining, but the parts are not installed, indicating to me that S&W doesn't consider them necessary for the 45 Colt level of recoil.

This is how my gunsmith (S&W trained) explained it to me. The cylinder stop is the only part in the gun that moves in two planes: Up and down to lock and unlock the cylinder and front and back to engage the trigger. Under heavy recoil, the stop would move forward (against its spring's pressure) and as it did, the top of the stop (which engages the cylinder notch) would "climb" the forward ramp of the notch enough to cause it to disengage. Then the torque of the gun's recoil would spin the gun around a (relatively) stationary cylinder. The longer notch prevents the stop from climbing out of the notch. The additional lever in the action doubled down on this by physically preventing the stop from "bouncing" out of the notch.

You'll notice that the longer notch became universal on all N frame cylinders regardless of caliber at about the -4 time (maybe sooner). This was likely for cost purposes; however, there is no identifiable advantage to retaining the short cylinder notches on any gun. The side benefit is that when the 625 (45 ACP/45 Colt), 657, 627, etc. are loaded hot with heavy bullets, the notch modification alone largely eliminates the possibility of the cylinder coming unlocked. Pretty elegant actually.

Keith

My first Redhawk, which I bought used, did that reverse trick a couple of times too. The guy told me that he had replaced the hammer spring with a weaker spring to reduce trigger pull weight. I replaced the weaker spring with the original spring and it never has done it again.

I also had a Taurus K frame copy in .44 Sp. that did that and no amount of spring swapping helped.

Thanks for everyone's insight on this. I'm hoping this problem wont occur tomorrow when I hit the range with some lighter 180 gr Remington ammo. I'll keep you posted tomorrow evening.