M48 Light Hammer Strike

[damnesia]

Hello. Long time listener, first time caller....

I've been an acquirer of firearms since I was a kid, but mostly old rifles and shotguns. Was not really that into sidearms until I was purchasing a couple Savage 1899s out of a collection and ended up with 3 S&W revolvers as part of a package deal because my wife was interested in two of the revolvers and I had been thinking of getting a .357 for awhile. I got a M48 no dash, M13-1 and M12-2. The M48 and M13-1 were duracoated or ceracoted to look stainless but I paid about $100 each for them and figured they would make good shooters. The 13-1 is the best pistol I've ever shot. I can't say enough good things about it, it's just perfect for me maybe. My next S&W is going to be a 1905 in .32-20 because I have more than a few rifles chambered in that round. And I plan on getting another M13. Also have a 4516 I really like.

Anyway, the M48. From SCS&W puts it as being made in 1959. It's fun to shoot and is my wife's favorite gun. I'm going to either blue it myself or have it blued. I've rust blued a lot over the past 20 years and have gotten pretty good at it. And am considered good at metal refinishing. Not sure how to get the coating off it, which is the reason I may pay someone to do it. Before it gets refinished I need to take care of one problem. Seems it has a case of light hammer strikes. It was doing it about 50% of the time on the first strike, but then the round would go off on the second strike. If it matters I only really single action shoot. So I completely took it apart and cleaned it. It hadn't been cleaned in a loooong time, but appeared to have been generously oiled often. So got it cleaned up, reassmbled and test fired it. Action was a lot smoother and it only wouldn't fire about 25% of the time.

My thinking is that the main spring is worn out. Does this actually happen? Another thought is someone replaced the main spring with a lighter one. I suppose someone may have shortened the tension screw but I'm fairly certain that is not the case. I've only tried Winchester 22mag ammo, but have tried ammo out of different boxes with the same results.

My question is, is purchasing a new factory power Wolff spring the right next step?

Thanks.

 

[Retired W4]

I say go for it, if you are sure the strain screw has not been shortened. I have used Wolff springs in my shooters with good results. I'm usually putting in reduce power springs being mindful of light strike with a variety of ammo brands.

 

[damnesia]

I say go for it, if you are sure the strain screw has not been shortened. I have used Wolff springs in my shooters with good results. I'm usually putting in reduce power springs being mindful of light strike with a variety of ammo brands.

Is there a standard measurement for the strain screw? If it does have the original spring in it, I'd like to keep it.

 

[Retired W4]

Not that I can find in my books. You might have better luck posting your question in the smithing section. There are several experienced armorers there who could help.

The 48 is on my "looking for" list these days. I have owned two, but sadly I sold them.

 

[series guy]

If you post a photo of the grip frame with the stocks removed we can see the arch of the mainspring and it will give a good indication of proper strain screw length.

 

[damnesia]

I thought I'd get an email if someone posted to my thread but I did not. Glad I checked. Let me know if this picture is good enough to see the arch of the spring.

Thanks.

 

[mh51]

Cylinder end-shake (forward-backward play) can also be the culprit. With the gun empty, let the hammer down into the fired position and hold the trigger to the rear. Attempt to move the cylinder back and forth. Do this for each chamber. If you find noticeable play, a new spring may not be the cure.

 

[ReloadforFun]

Are the misfires with factory ammunition or reloads?

The characteristic of a misfire firing on a second firing pin strike is commonly seen when the primer is not fully seated. Rare with factory ammunition, somewhat more common with reloads.

 

[dsf]

I thought I'd get an email if someone posted to my thread but I did not. Glad I checked. Let me know if this picture is good enough to see the arch of the spring.

Thanks.

Looks like there should be a bit more bow to that mainspring.

 

[damnesia]

There might be a tiny amount of end shake on one cylinder. I tried measuring with a feeler gauge but I couldn't find one that was thin enough, so if there is end shake i think it's like .001 max. Would that be enough to cause the problem?

These are .22 magnum factory loads.

Maybe I'll look for a new tension screw. Is this something I can find in the proper length or will it require tweaking to get it adjusted?

Thanks.

 

[4barrel]

Don't try to bend the spring. You can back the screw off and install a spent large primer under the screw and retighten until you get a new spring.

 

[Jim Watson]

I would get a fresh S&W spring, the Wolff lets the strain screw drop down in the groove and reduce the preload.
An 8-32 set screw will let you apply as much strain as you like.

 

[stu1ritter]

For strain screw and hammer spring questions read http://smith-wessonforum.com/s-w-sm...html?highlight=Revolver+Trigger+Job+Questions which shows the S&W Armorers manual answers to your questions.

Stu

 

[Hair Trigger]

Are the misfires with factory ammunition or reloads?

The characteristic of a misfire firing on a second firing pin strike is commonly seen when the primer is not fully seated. Rare with factory ammunition, somewhat more common with reloads.

OP is shooting .22 Magnum Rimfire. No separate primer to seat, and not reloadable.

How tight are your chambers? Will your rounds drop in easily and seat fully without pushing them? I have a similar issue to yours with my M48-4, a good deal newer version (mine is from 1981). If there is the least amount of powder residue in the chambers, the rounds don't fully seat, but look like the do, the back of the case head is still flush with the cylinder, to look at them. I'll get one or two FTF's on a cylinder, but they always fire the next time around, from being driven to fully seated by the previous hammer strike. If I look at the failed cases before trying the second time, the pin strike looks just as indented as the ones that fired. I've only shot CCI ammo in mine.

This happens on either single or double action, and only starts after the 3rd cylinder load or so, after starting with a clean gun. If I blow out the chambers between reloading, I get much fewer FTF's which leads me to think mine is an issue with the rounds not properly seating. My chambers are fairly tight and even when clean, I have to push the rounds into a seated position. Mine has no end shake and the action is tight, and strain screw properly tight. I don't think my gun has been fired very much before I bought it, no usual wear on the finish and cylinder looks "unused" for lack of a better description.

I love shooting this gun, it's very accurate, but the issue is irritating.

 

[gkitch]

I had this problem on my Model 48 and solved it simply by shoving the rounds all the way into the chambers.

What was happening was the rimfire rounds were taking the first strike (about half the time) to SEAT them and the second hit would fire them.

The magnums are long and need to be purposely seated. I think you may find this solves much of the issue.

 

[damnesia]

I bought a new spring from midwest gun works and a tension screw too. The screw looks like it was for a round butt even though it was stated to be for a square butt, it was way shorter than the one in the gun. So I replaced the spring. The new one was about identical but had a slightly differ bend at the top. The hammer pull is now more stiff and after firing 50 rounds through the gun, every round fired as expected. I like the feel of it with the new spring too. And I like that it's a flat spring with no rib.

 

[wheelgun610]

I bought a new spring from midwest gun works and a tension screw too. The screw looks like it was for a round butt...

Do you have another square butt K frame you can compare strain screw length with? And did you clean under the extractor star? If there's any gunk at all under the extractor, it can act like a cushion when the firing pin hits the rim of the cartridge. It's usually worse with .22 LRs than with .22 Mags due to the lube on bullets, but it needs to be well cleaned - even with magnums.

Mark

 

[merl67]

Welcome to the forum sounds like you got your problem sorted out. It also sounds like you got some good shooter grade guns to boot. The old 99 Savage rifles were a marvel of engineering. Perhaps you could post pictures of those in the appropriate section of the forum

 

[damnesia]

Do you have another square butt K frame you can compare strain screw length with? And did you clean under the extractor star? If there's any gunk at all under the extractor, it can act like a cushion when the firing pin hits the rim of the cartridge. It's usually worse with .22 LRs than with .22 Mags due to the lube on bullets, but it needs to be well cleaned - even with magnums.

Mark

I have a model 13, which I believe is a K frame, so I may compare the screws.

I did clean under the extractor when I deep cleaned the gun. It's very clean.

 

[damnesia]

Welcome to the forum sounds like you got your problem sorted out. It also sounds like you got some good shooter grade guns to boot. The old 99 Savage rifles were a marvel of engineering. Perhaps you could post pictures of those in the appropriate section of the forum

Thank you, it's good to be here.

The 99s are my favorite rifle of all time. I may post some pics if I can find where they should go. I've got 33 of them, so will only post pics of some of the good ones