Hammer Block Question

[Andy Taylor]

Ok, I know the story of the WWII sailor who was killed when a Victory model was dropped and it discharged because the hammer block failed. I know that this lead to an improved version of the safety device.
What I am wondering is how exactly do both versions of the hammer block work? Why is it that the earlier version failed? What was done to the newer version to prevent that failure?

 

[Muley Gil]

If you take a modern S&W revolver, you can cock the hammer and LIGHTLY touch the trigger, and the gun will not fire. My instructor at the police academy showed us that, using a pencil to "bump" the trigger. The trigger has to be held back at the moment of firing to make the firing pin to protrude through the recoil shield and strike the primer. Otherwise, the block keeps the hammer back enough to prevent firing.

If you disassemble a Smith and look at how the hammer block moves during the single or double action cycle, it is easy to see.

 

[DCWilson]

To add to what Gil said about modern design, let me try to describe what went on in the previous version of the hammer block. There was a piece of metal in a groove in the sideplate that was held forward by a spring. A protruding nub fit into the hammer's path of travel on the right side -- it did not completely cross the front of the hammer.

When the trigger was pulled or the gun cocked, the rising hand pushed this block back into the sideplate slot against the spring tension. After the trigger was released and returned to its forward position, the hand dropped and the hammer block was pushed back into safe position.

The problem with this was that if the gun was fired a lot and not maintained, the sideplate slot could get gunked up with grime and hardened lubricants. The block could get stuck in place and would not move fully back into position when the trigger returned forward. Note that you didn't need to have a completely frozen hammer block. If it moved back, but only partway, it might not present enough surface contact to keep the hammer from moving forward with a sharp blow on the spur.

In terms of action, the old block slid in from the side to block the hammer's forward motion; the new block, driven by the motion of the trigger rebound slide, was pulled down so that a rabbeted portion of the hammer face would line up with the block when the hammer fell on a cartridge. With the trigger in forward position, the block lined up with the unrabbeted portion of the hammer face and prevented forward motion.

 

[haggis]

Charlie Pate's book, U.S. Handguns of World War II, The Secondary Pistols and Revolvers, includes Appendix F which covers the testing and documentation of the new hammer block. There is an interesting comparison of the new S&W hammer block with both the old hammer block and the Positive Lock on the Colt Commandos.

Buck

 

[BaldEagle1313]

If you take a modern S&W revolver, you can cock the hammer and LIGHTLY touch the trigger, and the gun will not fire. My instructor at the police academy showed us that, using a pencil to "bump" the trigger. The trigger has to be held back at the moment of firing to make the firing pin to protrude through the recoil shield and strike the primer. Otherwise, the block keeps the hammer back enough to prevent firing.

If you disassemble a Smith and look at how the hammer block moves during the single or double action cycle, it is easy to see.

I don't mean to hijack the thread, but my 28-2 6" seems to have a hammer block issue. Double action is quite heavy, but single action will fire if you breathe hard. I mean, it seems like just resting your finger on the trigger will fire it. I hear a little rattle inside, and when I pulled off the sideplate the hammer block is loose. When I cock the gun to see what the hammer block is doing, it doesn't line up like you are describing; it just kind of moves around like it has no purpose at all. I looked at a schematic and it does appear to be in the proper place; it's just loose.

Or should I just copy this question into a new post in the gunsmithing section?

 

[john traveler]

The bottom end of the hammer block has a diagonal groove that rides on the pin at the rear of the rebound slide. Rearward motion of the rebound slide cams and lowers the hammer block, and forward motion raises it.

If the pin is missing, the hammer block will not function properly.

 

[BaldEagle1313]

If the pin is missing, the hammer block will not function properly.

The pin is there, and in the proper place in the hammer block slot. It just looks like the hammer block is too short. It doesn't go all the way up to the rabbet in the trigger. I got it used, for a real good price, so I suppose I can't complain too much. I just don't like hearing a gun rattle inside. That, and the super-light single-action trigger pull seems almost dangerous.

 

[Texas Star]

The pin is there, and in the proper place in the hammer block slot.. It just looks like te hammer block is too short. It doesn't go all the way up to the rabbet in the trigger. I got it used, for a real good price, so I suppose I can't complain too much. I just don't like hearing a gun rattle inside. That, and the super-light single-action trigger pull seems almost dangerous.

Someone has "worked" on your gun and buggered it. Don't cock the hammer with the gun loaded until you have it repaired. Your bargain gun is going to cost you some money, if you can even find a qualified gunsmith to fix it. Maybe the factory will still do that. I've read that they will still work on most revolvers with a number, so if yours was made in 1957 or later, it will be a Model 28 and qualify.

I think your sear area has been tampered with. Depending on what was done, you may have to replace the hammer and or trigger.

Someone probably knowingly sold you a gun that is dangerous. Hence, the low price. But the gun is a good one, worth repairing and enjoying for years to come!

 

[john traveler]

Texas Star gave good advice.

Some gunsmiths removed the hammer block entirely in the belief that it smoothed and lightened the trigger pull. What it does is remove the safety feature that protects the gun from discharge if the hammer is struck or the gun is dropped on it's hammer.

When it was replaced, a K frame hammer block may have been installed.

At any rate, S&W can make it right and restore the marginal SA trigger condition.

 

[BaldEagle1313]

At any rate, S&W can make it right and restore the marginal SA trigger condition.

Gentlemen, thank you for your prompt and sage advice. I guess my next question then is how does one go about sending a firearm back to S&W? I'm sure you have to contact them ahead of time rather than just shipping something back blind. Does Lee have a "sticky" for that?

 

[Muley Gil]

Yes, I would contact them first and describe the problem. Even though the revolver is over 30 years old, they might send a shipping box to you. I know the company doesn't want an unsafe revolver out there.

Smith & Wesson

 

[geneboy]

I don't mean to hijack the thread, but my 28-2 6" seems to have a hammer block issue. Double action is quite heavy, but single action will fire if you breathe hard. I mean, it seems like just resting your finger on the trigger will fire it. I hear a little rattle inside, and when I pulled off the sideplate the hammer block is loose. When I cock the gun to see what the hammer block is doing, it doesn't line up like you are describing; it just kind of moves around like it has no purpose at all. I looked at a schematic and it does appear to be in the proper place; it's just loose.

Or should I just copy this question into a new post in the gunsmithing section?

extremely light single action trigger can be caused by installing an 11lb trigger return spring, I do this all the time BUT ONLY ON DOUBLE ACTION ONLY guns. Check the return spring. It may not be the block at all

 

[linde]

The bottom end of the hammer block has a diagonal groove that rides on the pin at the rear of the rebound slide. Rearward motion of the rebound slide cams and lowers the hammer block, and forward motion raises it. If the pin is missing, the hammer block will not function properly.

The pin is there, and in the proper place in the hammer block slot. It just looks like the hammer block is too short. It doesn't go all the way up to the rabbet in the trigger.

There is a slot in the side plate in which the hammer block travels. With the side plate off . . . even with the pin in the rebound slide . . . the hammer block will not appear to travel up to its proper place. To verify you have a proper N-frame hammer block, replace the side plate, cock the unloaded hammer, and examine from the top to see if the block traveled to where it should.

You've received some sage advice on that light SA trigger . . . have the sear inspected by a qualified gunsmith &/or the factory.

Good luck,

Russ

 

[6 Cylinder]

May I jump in with a question on this subject? My 629-6 out of the performance shop, purchased new with less than 2 boxes of ammo through it would not always return the trigger & never if pointed up. Part of the probable was some glue looking stuff on the trigger block. I cleaned that up and it helped but not if the gun was pointed up. I removed the hammer block and the gun trigger returns perfect in all positions. Does the hammer block only serve as safety if the gun is cocked? Thanks!

 

[Protocall_Design]

The trigger block is a safety if the hammer is not cocked as well. With the hammer in the resting position, if the gun were dropped and landed on the hammer spur, it would still block the hammer. The rebound slide also blocks the hammer in the same place, but I have seen cases where the bottom part of the hammer broke off, so the gun would have fired if not for the hammer block.

 

[Hondo44]

The most common problem for lack of trigger return is the trigger rebound spring is too weak. And you've kind of proved that since it works w/o the additional weight/friction of the sliding bar to move.

The rebound spring is inside the rebound slide. Send gun back to Smith or ask for a couple of springs be sent to you; one same weight as yours is supposed to be and one slightly heavier.

 

[model3sw]

the first suggestion is to bring it to a qualified gunsmith. If you feel confident of your mechanical skills, then you can try to resolve it yourself.

A good cleaning of all the internal gunk is the first step then visually check the hammer / sear engagement. It may simply be the gunk as the main issue or you may need to have the sear engagement sharpened but first a good cleaning is in order.

After decades of sitting the grease used during manufacture often solidifies to the point where the hammer cannot even be cocked nor the cylinder release latch manipulated properly ... as if glued together (in one extreme) or could be in various degrees of gunk accumulated and / or various and / or sporadic malfunction issues.

The caked up, solidified grease may be bridging the hammer / sear engagement actually de-emphasizing the hammer / sear sharpness ... or (as Jim indicates) you may need new springs but if you're going to service it, may as well change the springs while you're in there.

Usually a flood bath of WD 40 or a good penetrating oil will remedy the problem when first observed. All that old grease should be cleaned out properly by removing the sideplate to access the matter.

After a thorough cleaning out of the gunk, the completely blow dried (compressed air), place a nice dab of synthetic, high heat, bearing grease will both lubricate and resolve that rattling issue (which is usually the hammer block safety arm rattling against the sideplate) if all internal parts are OK. My son came to me a few months back with a 629 to listen to the rattle when he shook it. It is a lot more common than you'd think.

If you find something physically broken or seriously worn, internally, you must correct that first. Otherwise, this would be the most common issue (causing your problems) and the fix.

OH ... I have seen that safety arm re-installed improperly (cannot remember, either backward or upside down) that I cannot even imagine how the sideplate was ever re-seated.