38 S&W Top Break Trouble

[Retired W4]

A buddy handed over the gun to see if I could figure it out. In single action it will not lock back. Works DA, sort of. It appears to me that the hammer spring is too long and the stirrup and spring jam against the curve in the rear of the hammer preventing it from locking back. The hammer spring is shorter than one for a HE, but not short enough it seems. SN is 490520. Any ideas?

 

[Retired W4]

An illustration of the problem. Note the position of the stirrup when hammer is at rest and when the hammer is back. The hammer/stirrup contacts the rear surface of the hammer before the SA notch is engaged. It would probably function if the spring was 1/3" shorter. The spring appears to be for a J frame HE. Do these top breaks use a shorter spring?

 

[Alk8944]

Definitely not a J Frame spring, they are all coil springs!

 

[Protocall_Design]

A longer strain screw would fix it. If you don't tighten the strain screw enough on a K,L, or N frame, it will do the same thing.

 

[glowe]

That is the first thing I thought of. There is nowhere near enough curve on the mainspring. My recollection is that when these 38 DAs and 44 DAs were at full cock, the spring almost touched the rear section of the butt-frame. These guns require a long and hard pull to work in DA and modern day shooters want them to work easier. Shortening the strain screw is a popular way to lighten the trigger pull, but there are lots of unintended consequences to that "fix".

You can add a piece of hardwood or brass to test this theory. It looks like it will require an 1/8' thickness or more to put enough tension on the spring to pull it rearward at the sturrup.

That revolver has been re-plated including the trigger and hammer, sometimes making the full cock sear push off. Whenever I see these antiques polishes and re-plated, I wonder what else was done to them at that time.

Added: Found a picture in my collection file of the spring on my 44 DA, but is the same issue for any other top-break. This one has a cork insert with copper plate on the screw end to get enough tension to function properly. I bought this one that was buffed and chromed, including hammer and trigger as well. Spring was way to weak to even set off the primers in the ammo. Handsome revolver, plus you can check your teeth in the reflection!

 

[2152hq]

I don't think the tip of the strain screw is even touching the main spring in the pic. The tip of the screw looks to have been filed or ground off to a taper w/a small flat point to it.
Likely shortened at some time.

Back off the screw and insert a fired primer over the tip of the screw (primer minus the anvil)
The open cup end facing forward, that will keep it securely on the end of the screw.
Often the very slight increase in length that primer matr'l adds to the screw will be enough to 'fix' the problem.

If it needs more, then you can sort around for a more suitible extension for the screw tip. Or extend the tip with a pin inserted into the tip in a blind hole, soldered in place or even Locktite used.
Then file fit to length

I've seen them fixed with a simple blob of HardSolder deposited onto the end of the screw as well. The length is file fitted as above.

Remember that any permanent extension must be of a diameter to allow it to pass through the frame,,it must be just under the thread minor dia.
It's only job is to place pressure on the mainspring and bow it outward. So there is nothing fancy really needed.

 

[Retired W4]

Thank you all for the insight. The screw, which doesn't appear to have been shortened was impinging on the spring, but not enough, by a long shot. I grabbed a penny out of my pocked, tightened the strain screw onto it and it is fine now.

Now I just have to grind the penny down so I can get the grips on. Just kidding. Thanks again.