Light primer strikes, S&W K

[zxcvbob]

I've been having trouble lately with my S&W 15-4 not setting off the primers until the 2nd or sometimes 3rd hit. The first thing I did was make sure the strain screw was tight (it wasn't, I tightened it and the problem went away briefly then came back) The primers appear to be seated below flush, and my Ruger revolver sets them off just fine -- but the Ruger is probably oversprung. I'm having the same problem with Tula SP primers, Federal SR's, and lastly CCI SP's. (I still have Federal SP's to try, but I don't have many of those so I haven't tried them yet) It's all Winchester brass. I had about a 10% or 15% failure rate last night with the CCI's. I'm shooting double-action. I checked the strain screw again and it's still tight.

I've ejected one of the duds and the primer dent looks light -- just like it might if the primer had been high.

The gun club has a model 14 that i can borrow next week to help determine whether it's the ammo or the gun.

Are there any other adjustments on a S&W revolver that could cause this? maybe the headspace is off? The cylinder gap looks unusually close; maybe that's *not* a good thing...

 

[rcmodel]

My first guess is, the strain screw has been Bubba cut off to lighten the pull with it tight.

See if they will let you trade strain screws with the model 14, or at least compare them for length.

It could be excess headspace, but end shake would have to have gotten so far out of hand the cylinder would be rubbing hard on the barrel shank.

rc

 

[zxcvbob]

Last time I cleaned the gun I took the cylinder off (front screw on the right side of the frame.) First time I've done that, I didn't unscrew the ejector though. Should I have used a feeler gauge to set the cylinder gap when I put it back? Like I said, it looks tight; almost too tight, but it doesn't rub.

I don't see any wobbles or other weird movements when I dry-fire it.

I'll measure the strain screw. I *could* put a little metal shim under it if it's too short. The grips would keep it in place.

 

[rcmodel]

No, taking the cylinder assembly off for cleaning cannot possibly change anything, if you put the same screw back in the front hole it came out of.
But even then, a different sideplate screw would not change the headspace, it would just maybe make the cylinder hard to open.

I have heard a spent primer cup makes a good shim that can't fall off the screw but have never tried it.

But I would not do that until you are 100% sure the screw has been shortened.
Too much shim could over-stress the flat spring and bend or break it.

rc

 

[zxcvbob]

I only took out the one side-screw, and I put it back.

I've also be told I should try cleaning my primer pockets.

 

[rcmodel]

Well, unless they are way more dirty then any I ever saw, that won't cause a K-Frame misfire.

If the spring & strain screw is up to spec, it should fire anything you put in it every time.

Just another thought, but you might read this.
I had no problem in any of my S&W's, but this Colt sure didn't like what I found in my brass collection.
http://www.thehighroad.org/showpost.php?p=6966298&postcount=1

rc

 

[gamestalker]

I've got 2 K frames that both had the problem. I first replaced the main spring and strain screw and things improved a bit. And I didn't have any head space issues either. I also replaced the firing pins with extended one's and still had intermitent issues. I finally had to have the hammer's taken down a tiny bit (.002") to increase travel and the problem completely went away. This is a last resort and must be done perfectly or you'll end up with other issues like over travel being enough to impact the F.P. when the hammer is free dropped and or, resting on the F.P.. And if the smith isn't very precise, you'll also have allignment problems causing the hammer to rub on the side plate or frame. If you know a good smith you can also eliminate the problem by having him make you a F.P. thats .002"-.003" longer than the extended one.

I don't know why S&W's are so prone to this problem, especially when using DA. I've found this to be a rather common problem with them.

 

[Red Cent]

"I finally had to have the hammer's taken down a tiny bit (.002") to increase travel and the problem completely went away."

Curious. Where did you remove metal?