M10 hammer slips off the sear

[meshugunner]

I have an old S&W Model 10-7. When I cock the hammer on the SA sear, I can force it to release by strong thumb pressure on the hammer.

Is this a problem? If so what can I do about it?

Thanks

[fourarmed]

Probably depends on how much force is required to push it off. In extreme cases the hammer releases so easily on single action fire that the rebound slide spring will kick the trigger forward fast enough to catch the hammer at half cock. Even if it doesn't catch at half cock, the contact can slow the hammer fall enough to produce misfires. I had one like that, and by following the stoning instructions in Kuhnhausen's S&W book, I was able to fix it with just a couple of strokes of the stone in the proper direction. If you have any doubts about your skills, I would send it back to Smith. You might have a local gunsmith who could fix it properly, but if you send it to the factory, it will be done right.

[Mk42gunner]

The condition is called "Push off," and yes it needs to be fixed.

Any reasonably competent gunsmith or revolver armorer should be able to fix this for you.

Good luck and be safe,

Robert

[roysha]

Often time this situation is created when someone does an "action job" and puts in a too light trigger spring. This occurred much more often before the advent of the quality spring kits we have today when the most common "adjustment" for lightening the trigger pull was to clip a couple of coils off the spring. Depending on the age of your gun, it is possible that this has been done.

Before you spend a lot of money, and assuming you are reasonably competent, I suggest replacing the spring. While stoning is an option, one had best know exactly what they are doing to avoid a truly costly repair. Also, depending on the age of the gun S&W may or may not support it.

[fourarmed]

I will have to disagree with roysha to a certain extent. "Push off" or "trigger kick" can occur with a full power rebound slide spring. When it does, the slightest pressure on the trigger releases the hammer, and then the rebound slide spring kicks the trigger (and your finger) forward, where the hammer can catch at half cock. The problem is the angle of the SA engagement surface on the trigger. The two may be found together, of course. If someone stones the trigger too light, they may then clip the spring to stop the trigger kick, but the fundamental problem is the trigger engagement surface.

[meshugunner]

Thank you everyone for your advice and comments.

I gave this gun to a local smith for an action job. I don't know whether it had this problem before I gave it to him but I feel he should have checked for it before and after working on it and having found it, he should have fixed it. The gun also delivers light strikes about 50% of the time. Something it did not do before I had it worked on. I'm not going back to him. I reinstalled the factory hammerspring since I have found that too light a hammer spring can cause this but it didn't change anything. I haven't tried the trigger return spring.

IIRC this gun was made in the 70's. A 4" pencil bbl. It was a service revolver. When I bought it, the insides were as dirty as a car engine. After cleaning, it looked to me like the gun had not been shot much. Often the case with duty guns. Another reason to think the gun's action was in close to factory condition when I bought it.

It is now in the hands of another smith with a very fine reputation and whose prices are very reasonable. He seemed to think it would be easy to fix. I am guessing he expects to stone the contact surfaces. I do most kinds of basic work on my guns but I stay away from stoning critical surfaces for fear of doing what the first gunsmith did to this gun.

[fourarmed]

A situation like this is one place where the guy who jerks the trigger won't have misfires, while the guy who steadily increases pressure until the hammer falls will. I was shooting with friends last week, and one guy had a Series 80 1911 that repeatedly misfired for me, but almost never did for the other guys. I started jerking the trigger, and it stopped misfiring for me. I think the problem was an overtravel screw set too close, and maybe a leg on the sear spring not quite right. He had also done some stoning on the hammer and sear. The same thing happens with trigger kick. If you yank the h--l out of it, you overcome the trigger return spring and the half-cock notch doesn't catch the trigger.

[roysha]

I knew that I was a slow learner but I didn't realize just how slow till now. After 45+ years of shooting and working on S&W DA revolvers I have learned from this thread that the hammer has a half cock. Oh well, better late than never.

[HeavyMetal]

I want someone to post a picture of a K frame hammer with an arrow pointing to the half cock notch!

Never seen one on any K or N frame Smith and I guess I needs to see the proof!

Next thought: Push Off??? If you can put incredibley light pressure on a cocked K or N frame gun and the sear "pops" out of the notch you got a problem! If you need both thumbs and a little grunt to get this to happen ya needs a slap on the back of the head!

I saw this little "tip" in Shooting Times years ago and I betcha more hammers have had the notchs destroyed by this little test than all the shooting the particular pistol has ever done!

I'll quote Ben Franklin: common sense is an uncommon virtue! we need more of it!

[roysha]

HM, I agree with you 100%! I hope you realize my last post was a "tongue in cheek" sort of post.

[meshugunner]

In the case of this gun, all that was required was firm pressure from my thumb. I did not even experience any discomfort from pressing my thumb against the back of the hammer. I do have strong hands and probably could damage a working SA mechanism if I really wanted to but I have some feel for machinery and I would not have applied excessive force. The same pressure on my other revolvers does not release the hammer.

While it is definitely possible the hammer could be bumped off the sear accidentally, it's quite unlikely. For SD I fire my revolvers DA only. Anyway, this is a range gun not a carry gun. I don't cock the hammer until I am facing a target so I find it hard to see how this by itself could cause a problem.

However, there is the issue of light strikes with DA which wasn't present before the "action job". This needs fixing and if, as suggested, it's another symptom of the sear problem then that has to be corrected.

Also, I would like to get the revolver "working right". I like to have my guns in perfect working order. And, I would like to be able to sell it as a properly functioning gun at some time in the future.

PS. I checked my M10 2" snubbie (since the gun with a problem is at the gunsmith) and I cannot get the hammer to half cock. I haven't taken off the cover plate.

[HeavyMetal]

I can understand wanting a safe pistol, LOL!

In your case I think your first smith over adjusted something. If you've had a good relationship.in the past an oppurtunity to do warranty is fair.

If this is a first.time visit. Maybe not!

[rintinglen]

Push off as meshugunner describes is almost always the result of a shade-tree gunsmith attempting to lighten the trigger pull. A proper stone and a steady hand can recut the engagement notch, but the case hardening will be compromised and the better path is new hammer. Otherwise, expect the problem to return down the road--in a few thousand rounds or so as the hardened trigger nose wears on the softer steel exposed.
A quick fix for the light hammer strikes is to first check that the main spring screw is fully tightened and then if that doesn't cure the problem, take a spent primer, pry out the anvil, loosen the mainspring screw until the primer cup will fit over the end of the screw and then retighten. Unless the mainspring was really altered, the added length will be enough to restore proper functioning.

[meshugunner]

Yeah I was worried about cutting through the case hardening. If this smith says it's an issue, I will buy a new hammer. I hear they cost about $60 but if I don't fix it, this defect will bring the resale price down quite a bit more than that. I certainly couldn't sell it without disclosing this issue.

As for the smith who did the original work, I am writing him off. Yes if I had a history of good work from him, I might well overlook an occasional bad day. But apart from the possibility that he did a poor job, what really bothers me is that he didn't check the gun properly before returning it to me. For all he knew I was going to depend on that gun and he let it leave his shop firing only about 50% of the time. There's more to this gun story.

The first time I picked it up after he had worked on it, I found the cylinder would rub against the forcing cone intermittently. I doubt he caused this, but he didn't spot it. Also, I was surprised at how much trouble he had diagnosing and fixing the problem. When I got it back from that fix, I found the push off problem.

I live in a rural area and it's hard to find good smiths who have any time for my guns. I bought the 2" M10 about the same time and I sent it out to Jim Reid at Lawson's in Tucson AZ. He is not fast and he's nearly deaf so I had to shout so loud on the phone that people could hear me in Tucson anyway, but he did a first rate job and he was very nice to work with (except for the strain on my vocal cords.) He's my choice for serious work from now on.

The 4" M10, the one with the problem, I picked up on impulse while shopping for the 2" snubbie. The finish was very worn and the gun was cheap. It looked to be a good shooter. I figured I would spend some time with it and then move it along. After a good cleaning I found it to be in better mechanical shape than I hoped - until this nonsense started.

[HeavyMetal]

Case hardening on S&W hammer and trigger are .015 to .018 not very deep!

The sear notch on both K and N frame guns is not very deep either and can be easily broken of should enough pressure be applied during a push off test.

I have always avoided cutting on a hammer, most of the time notchs are clean, but I have lapped a few sears and then dipped them in the case hardening compound Brownells sells.

a buddy worked in an aerospace company and he checked a treated sear to .040 depth when done with the Brownells product which I believe they call Case n it?

In all honesty most S&W can be improved drastically with nothing more than a spring change, particularly the rebound spring.

Another thing to keep in mind: Ed McGivern set all his records with untuned S&W revolvers!

Hope the OP gets his gun back without to much extra cost involved.

[meshugunner]

Hmmm... I do have some Kasenite in my shop. IIRC the piece has to be held at about 1000F for quite a few hours. What steel is the hammer made from? Why not just heat treat the whole hammer and draw temper on everything but the notch area? That way it would be hard all the way through. I am able to quench and temper steels that don't require a complicated schedule.

[fourarmed]

My comments about trigger kick and push off apply only to single action fire. And the poster who pointed out that there is no safety notch per se is correct. The problem is the safety bar that rises as the trigger goes forward. If you are having misfires on DA fire, then springs are almost certainly your problem. If the push off is not too light, and you don't get misfires in SA fire, I don't think I would do anything about it, especially if you mostly shoot DA anyway.

[bcp477]

" force it to release by strong thumb pressure on the hammer."

Certainly a "push off" problem ..... is never good. What do you mean by "strong thumb pressure" ? Almost any revolver hammer can be tripped, if enough pressure is used. Using a lot of pressure to test for a "push off" problem is a BIG NO NO. It can damage the sear surfaces - and CAUSE push off problems to develop, where they didn't exist before. Generally, no more than (roughly) 5 lbs of pressure should be used in testing for this. If your hammer holds with this amount of pressure, then it ISN'T broken - and DOESN'T need fixing.

If you've damaged the sear surfaces by excessive force used, then that is a different matter. If your 'smith damaged the surfaces, or over stoned them, etc..... then of course, the gun needs fixing.

Since the M10 is in the hands of a 'smith that you trust now, he should be able to take care of the issue, albeit with the possibility of new parts needed. 20/20 hindsight (and easy for me to say) - but sometimes, alterations like a "trigger job" just aren't worth it. I've never felt an M10 trigger that was that bad, really.

[jeff423]

If in the future you want to correct it your self here is the procedure. It's from the FAQ's on the smithing section of the S&W Forum. Scroll down about halfway. It works very well. I've corrected push off on two model 15-3's.

http://smith-wessonforum.com/s-w-smi...4072-faqs.html

Jeff

[KCSO]

As for tuning a S and W revolver...tuned for what? Yes you can lighten springs till the cows come home and you have a 6 poound double action pull but this is NOT what you want for a carry gun. The rebound spring is as heavy as it is for a reason, it helps push your finger back for reset for the next round. To light a rebound spring and you will skip past or it will slow your double action. 13# is about right for fast double action work. As to the mainspring for utter reliability you don't want a real light spring here either and don't ever let some dufus crank back the tension screw. The best smoothest double action in the world isn't any good if the gun don't go bang. Smoothing must be done very carefully also as it's easy to go right through the hard and ruin the innards. It takes me 1/2 a day to tune up a S Nad W and I have drawers full of spares just in case. My minimum teat is 50 rounds of small rifle primers without a singe misfire and then another 100 rounds of duty ammo.