S40 CCW Started Misfiring - out of battery

Thanks for providing this excellent forum.

I have a serious problem with my S40. It is (was) my primary carry piece until it started misfiring last week at the range. I started having failures about every 3-4 rounds. I took it home, stripped and thoroughly cleaned it according to the wonderfully detailed tutorials on this site. In particular, I removed and cleaned the extractor and firing pin/channel. I also lubed it well (lightly) with tetra gun grease.

I took it back to the range yesterday, and still had the problems. However, this time, I noticed that the misfires were caused by the slide not returning to battery. This occurred almost every other round or so. The variance ranged from about 1/16" to 1/8". If I manually pressed the slide forward, the gun would fire correctly.

When I got home from the range, I started playing with the slide by hand, to see if it would stick. If I gently moved it out of battery about 1/8"-1/4", it would remain about 1/8" away from the fully closed position.

I then disassembled the gun and looked for areas of wear or protrusions on which the slide might catch. In the center of the slide, beneath the firing pin channel, there is a pair of "rails" that contact the "catch" (#10 on the USASteyr schematic). At the rear end of these rails, right at the point where they bevel up into the slide proper, there are two wear marks. I ran my finger over those marks, and there is a barely perceptible protrusion that catches my finger. there is also a protrusion on either side of the rails, so that it appears as if the metal has been flattened and widened ever so slightly, like it has been deformed by the strike of a hammer.

I suspect that this is the cause of my slide sticking.

Now the question is, what should I do about it? Do I risk smoothing the rails out with a fine file or grinder (dremel), or is this a job for a smith? If either I or the smith screw it up, I think the whole slide is ruined.

I have about 1500 rounds through this gun, and it has been very reliable. My only problems with it until now has been its tendency to fail to eject when I forget myself and limp-wrist the gun. When I pay attention and keep a firm grip, that does not happen.

Please advise. If I can, I will try to post a picture or two.

Thanks in advance.

 

Hmm, I guess I'm not sure on this one, but I doubt that the problem is in the "rails" on the slide. I believe that those rails are there to pick the next round out of the magazine, and only the firing pin hits the catch. The first thing that I would check is your recoil spring. If it's worn out, it will cause exactly the situation you describe.

James

 

In case that's the problem, I have ordered a new spring/guide rod assembly, and a new firing pin spring. However, after only 1500 rounds, I'd think the spring would not be that well worn.

Thanks for your suggestion.

 

Re: Having similar problem

I wish that were the problem, because I'd just remove the loaded chamber indicator if it came down to it. Alas, I can get the slide to stick without any round chambered, or coming into contact with the indicator.

Thanks for your reply.

 

That was the very first thing I noticed when I got my M40 second hand. If there's a round in the chamber I can get it to stick outa battery about 1/8".

There is no sticking of the slide or any internal parts. The recoil sping is just too weak. Once worn, the recoil spring lacks alot of power in it's resting position. But once the recoil spring reaches it's uncompressed postition the firing pin spring is reachingthe end of it's compression. The worn, uncompressed recoil spring and the compressed firing pin spring (plus the step up needed to lock the barrel/chamber/round in place) cancel each other out.

If you remove the spring, reassemble the gun and cock it, you'll notice that the stiff firing pin sping will hold the slide out of battery with what I consider a decent amount of force. I belive the firing pin and recoil springs are balanced unevenly to begin with. The recoil spring also compresses 99% of it's movement while the firing pin spring only compresses about 55% of it's movment, thus retaining it's strength much much longer.

It only took my gun 600rds and now I've noticed the developing problem. The gun REALLY needs a stronger spring in my opinion. At least another 2lbs. Until a stronger spring it made, I've opted for a new spring with a couple washers between the base of the guide rod and spring.

 

Th0r, thanks for your insights here. It sounds like this is the right line of investigation for me. Unfortunately, the guide rod/recoil spring assy. and FP spring I ordered from USASteyr was cancelled because they were out of stock. I thought it was too good to be true when their website took my order.

How can I get a replacement recoil spring?

What other springs might serve as a substitute?

Does anyone even know the power/weight of the S40 spring?

Thanks all!

 

Thanks very much for your insights. My example of the "creep close" was just to show that I could reproduce the out-of-battery condition at will even without a round chambered. In actual use, however, the slide will fail to go into battery in about 1 out of three rounds. This is after I meticulously detail stripped and cleaned the barrel, chamber, and action.

Now that you mentioned it, whenever I manually chamber a round by racking the slide normally, the slide does go all the way into battery.

The problem has occurred when I used Winchester USA 165 grain FMJ, Winchester USA 180 grain JHP, and Mag-Tech 155 grain JHP. The latter is a pretty hot load that is claimed to produce velocities of 1250fps and energy of 500 ft-lbs.

I have used the Winchester FMJ regularly at the range for over a year without experiencing this failure, which is why I'm thinking the gun is starting to fail.

I am open to all suggestions, thanks.

 

Could ClipDraw Have Caused this?

I just had a thought (call the papers!)...

I have been using a ClipDraw http://www.clipdraw.com/ to carry my S40 on a daily basis for about the last 6 months. The clip is mounted on the side of the slide, not the frame. It occurred to me that the weight of the gun+loaded mag puts constant pressure on the recoil spring that is not normal in a regular holster, where the entire gun is supported.

Is it possible that this constant, but slight, pressure on the recoil spring might have weakended it, causing my current failures?

Thanks.

 

Re: Could ClipDraw Have Caused this?

Ok. Thanks very much for your reply.

 

Sorry to resurrect this old thread, but I solved my problem and thought I'd share the solution:

My suspicions were correct. The "protrusions" I mention above were really small nicks or cuts in the rails that feed a round into the chamber. I think they were catching on the edge of the mag ever so slightly. I used my Dremel and some polishing compound to very gradually smooth out the raised metal, and voila, no more misfires! After 100 rounds of testing with my carry ammo and two other kinds, I am now back to carrying my S40 full time.

Hope this helps.

 

thanks for the update.
we so rarely get good follow up on what ever happened to issues like this.

 

Matsaleh-
I'm happy to hear that you solved your problem.
I'd like to add that recently, after a cleaning, when I would gently cycle the slide by hand, the slide would not fully go into battery. I was able to completely cure this by lubricating the inside of the firing pin, where the spring is. I believe that if this area is totally dry, the friction of the compressed firing pin spring on the inside surface of the firing pin is a major contributor to the problem.

 

That's good info too. FWIW, I investigated that possiblity in my own case but it was not to be. However, I can easily see how it could contribute in general. The contact area between the FP spring and the inside of the striker does not appear to be as finely machined as the inside of the FP chamber.

I didn't want to gum up my FP with oil, so I used Tetra Gun Grease on my FP inside and out. Tetra is good stuff. The instructions say you should wipe it off completely and leave all contact surfaces dry. Apparently the material bonds with the metal at a molecular level and slicks it up real nice when it's dry.

Cheers.