sticky hammer block

C

coldcanuck

Inactive
I have a model 14 that recently started giving me some trouble. The gun is setup for PPC matches and, although I only use it as a back-up, it always seemed to function fine.
Recently I had a couple of misfires and the trigger was feeling kind of gritty. I stripped it down, gave it a good bath and reassembled it. I removed and replaced the side plate properly but, once the gun was reassembled, I found that the trigger, if it was eased ahead will occasionly fail to reset. I've had it apart and back together probably 30x since then. If I remove the hammer block. the gun functions flawlessly, I thought the hammer block might have gotten bent so I installed a new one. That made things worse so, I reinstalled the old one. I've polished and tweaked it at least a dozen time and it still sticks occasionally. I've thought about leaving it out entirely but I'm hesitant to disable a safety device. Anyone have any insight they would care to share?
 
Oh, boy, that is a toughie. I assume you checked that the hammer block is not rubbing on the sideplate. Is it possible that the hammer or rebound slide is worn so that the hammer is not being cammed back enough to clear the hammer block?

Jim
 
I'm gonna go out on a limb and guess something's askew with the rebound slide.

Could be the stud on the slide itself that holds the hammer block is a bit bent, or that the stud behind the slide is bent. I suppose it could also be a burr of some sort on or behind the slide that's causing a misalignment. The old hammer block may have slightly bent to accommodate a misalignment.

Could also be a bent trigger stud, but I think that's less likely. That would affect the trigger pull & return directly, but possibly also the alignment of the rebound slide.
 
As far as I know it's the stock spring and I think the rebound slide is ok although I can see that it's been polished. On an unrelated note I can see that somebody at sometime cut off some of the butt frame, I think maybe to use round butt grips?
I'll check stud alignment next.
Thanks for all the input everybody!!
 
"I found that the trigger, if it was eased ahead will occasionly fail to reset."

In looking at Kuhnhausen's book, in the troubleshooting section, trigger reset is not mentioned in relation to the hammer block.

I suspect that the hammer block is simply creating a symptom by masking the real issue.

You seem to state that the gun has been worked on before you purchased it, and for PPC games.

My immediate guess is that the problem centers directly with the rebound slide spring.

I'll further guess that it is either a lightened spring from one of the after market manufacturers such as Wolfe, or that it is the stock spring that someone has lightened by lopping off a coil or several.

The immediate, and cheap, test is to get yourself a pack of springs by Wolfe, and swap the one that is in there out for the heaviest spring in the pack (there are normally three).

If that solves the problem, go to the middle power spring, then the lightest spring, and use the one that works.

That said, you mention that you are "easing" the trigger back. Not sure why you'd do that, or what kind of situation you'd find yourself in in which you'd want to do that...
 
The trigger return spring (inside the rebound slide) might be the problem, but it would have to be right on the edge for the interference of the hammer block to be enough to tie up trigger return. (Remember the OP says the gun works fine without the hammer block.)

But any excess friction or interference with the hammer block will prevent trigger return. That is why the safety is "positive"; if it is not working right, the trigger will hang up and the will not function. (The old Colt positive safety works the same way, though there is more mechanism involved.)

Jim
 
'but it would have to be right on the edge for the interference of the hammer block to be enough to tie up trigger return.'

Exactly, which is why I said that the hammer block is the symptom that is masking the real problem.

I know this is possible because Coldcanuck's description matches, to a T, the experience I had when I worked on a friend's Smith Model 10 a number of years ago.

Trigger return was fine with the 15 and 14 pound springs. It was also fine with the 13 pound spring, until I noticed that I'd forgotten to put the hammer block in.

When I installed the hammer block, the extra friction caused trigger reset issues (but not with the 14 or 15 pound springs with the hammer block installed).

My solution was to polish and relieve the back of the rebound slide (making relief cuts in the back of the rebound slide is one of the few actions where a dremel IS appropriate in action work!), stone the hammer block, and stone and relieve the hammer block channel in the side plate.

I also polished the trigger and the trigger boss and installed a stainless steel centering washer on both the hammer and trigger bosses.

The end result after a few other tweeks was an exceptional trigger pull and 100% positive trigger reset.
 
Mike, you can hear the Hammer Block rattle around in there*, so I was thinking friction from a properly-functioning HB is negligible. If it's affecting the return when the return spring's light, then, it seems the HB's adding too much friction. Polishing the slide may have fixed it, but it suggests something's amiss with the HB, and it's still adding drag, no?

Personally, if (and only if) the gun's been converted to DAO, is set up for PPC, and is allowed by the sanctioning body, I'd have already removed the hammer block altogether.


* BTW, coldcanuck, can you hear the hammer block rattle around when you shake the gun?
 
"Mike, you can hear the Hammer Block rattle around in there*, so I was thinking friction from a properly-functioning HB is negligible."

Maybe.

Most people tend to listen for hammer block rattle when the action is at rest.

Remember, when the trigger is being operated, the hammer block is being moved by the stud on the rebound slide, meaning those parts are bearing on each other.

Because the rebound slide moves east-west, and the hammer block moves north-south, there's going to be shearing forces at play, which tend to set up a lot of friction.

That's where your extra drag is coming into play.


"Personally, if (and only if) the gun's been converted to DAO, is set up for PPC, and is allowed by the sanctioning body, I'd have already removed the hammer block altogether."

Not a good idea to remove the hammer block.

Converting the gun to double action only does nothing to prevent the gun from discharging if the hammer is struck or dropped with force sufficient to defeat the rebound stud.
 
Mike Irwin said:
Because the rebound slide moves east-west, and the hammer block moves north-south, there's going to be shearing forces at play, which tend to set up a lot of friction.
Click to expand...

Good point.

Mike Irwin said:
Converting the gun to double action only does nothing to prevent the gun from discharging if the hammer is struck or dropped with force sufficient to defeat the rebound stud.
Click to expand...

The hammer block primarily prevents contact with the firing pin if the hammer drops when the trigger's fully forward. It's role as a "drop safe" device seems redundant. Besides, a hammer cut flush (or close to) with the frame, is unlikely to get specifically hit if dropped. Add in the unlikelihood of dropping your gun at a PPC match, and the unlikelihood of the rebound system failing, and I'd lose more sleep over the possibility of a blown match due to failure of an unnecessary part.

Note that this isn't a general endorsement for categoric removal of the hammer block. Just sayin' that under some very controlled & very specific conditions, there's potentially more to lose by keeping it in, IMO.
 
"The hammer block primarily prevents contact with the firing pin if the hammer drops when the trigger's fully forward. It's role as a "drop safe" device seems redundant."

Correct AND incorrect.

I take it you're not familiar with the history of S&W hammer blocks.

Prior to 1944, S&W used a sideplate mounted (actually attached to the side plate) hammer block that was cammed out of place by the action of the hammer.

It was not, however, a positive action hammer block in that it could, through corrosion or dirt, go into the "off" (ready to fire) mode and STAY there.

This problem led to the death of at least one US Navy sailor who, while on guard duty, dropped his issue S&W M&P revolver. It fell on the hammer with enough force that either the hammer broke or the rebound slide hump failed (I'm not sure which).

The military directed designers at S&W and Springfield Arsenal to come up with a positive hammer block that would not fail and, if it did, would render the gun inoperative.

Springfield's people developed the hammer block that we known today.

By removing the modern hammer block for any reason on a gun that is not either hammerless or enclosed hammer is NOT a good idea.


I've never understood why people remove the hammer block from modern S&W's. To me, it's of the same logic that "removing the brakes from my car will make it go faster!"

It's short sighted and it's stupid, even on a range gun.

And, I'm not at all familiar with PPC rules, but I can't conceive of any competitive shooting sport that would incorporate, as part of its play rules, a section that would in essence state: "It's perfectly OK to remove the manufacturer's safety devices. We know you're careful."

So, to my way of thinking, that very controlled situation doesn't exist.
 
Mike - we agree it's unlikely any sanctioning body would be ok with removal of the hammer block on any gun, so I think we can agree discussion on the matter is/was largely moot, then. ;)

I'm interested to hear what the OP finds is the root of the problem.
 
Both the previous types of S&W hammer blocks were functioned by the hand, not the hammer, but the description of the failure is correct.

While there should be some friction involved in operating the hammer block, it would be at the stud in the rebound slide. The vertical part of the block moves (or should move) so freely that friction will be near zero. On a number of occasions, I have tested the DA pull/SA cocking of an S&W revolver without the hammer block and again with it installed. I have never been able to feel the difference and a trigger pull gauge shows no significant difference.

Influenced by some "experts", I once thought that removing the block was necessary to get a good DA pull; I long ago changed my mind and have never removed one since. In fact, I put back a couple I had removed in my own guns.

Just to cover another common belief, that a transfer bar is better than a hammer block. In practice, there is no difference in doing the primary job of providing safety. But a transfer bar is struck by the hammer every time the hammer drops, and they have been known to break from metal fatigue, although careful fitting can minimize that concern. A hammer block safety, on the other hand, will never be struck in normal operation; if it is hit, the gun has already been subjected to serious and probably disabling damage.

Jim
 
Crap, I did say hammer. Early morning...

These are pictures of part of one of the earlier hammer blocks. It's from my Regulation Police, made in the early 1920s.

25821082.jpg


25821322.jpg


At rest, the hammer block pin rests in the notch in the hand. That allows a properly operating hammer block (I call this version the "wing" hammer block) to move out to where it will block the hammer.

When the hand begins to move, it cams the pin backwards, which in turn pushes the hammer block out of the way of the hammer into what I call the OFF position.

When the trigger is released, the pin slides back into the notch in the hand, and the hammer block SHOULD move back into position to where it will block the hammer.

If the system is dirty, full of gunked up oil, or rusty, the hammer block can jam in the OFF position, either on its own or because the pin sticks, rendering the hammer block system inoperative.
 
Right, Mike, that is the earlier one and was used starting c. 1915. Note that the coil spring also served as the hand spring so the hand spring in the trigger was eliminated. In 1926, a different hammer block came into use. It also was operated by the hand, but used a sloping surface on an enlarged hand to push back the hammer block. That was the type that failed in WWII and was replaced by the current system.

As I understand it, the current system was primarily designed by Carl Hellstrom, aided by a few machinists, not by a large design team. There may be a better system, but what works, works.

Both the older types had problems; they depended on springs and, as you mentioned earlier were not "positive". Not only could dirt or hardened grease stop them from working, but the hammer block itself was a spring and could break.

Jim
 
"As I understand it, the current system was primarily designed by Carl Hellstrom, aided by a few machinists, not by a large design team."

I never said large design team.

I said designers at S&W and Springfield. That could be as few as two or as many as 10,000.

It's also my understanding that the modern hammer block was developed not by S&W, but by Springfield Arsenal.
 
Interesting, Mike. That is the first I have heard of Springfield Armory being involved in any way except possibly to approve the change. Do you recall where you got that information?

Jim
 
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