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View Full Version : New PM40 slide locks open with rounds in magazine



smokey337
12-27-2010, 09:08 AM
Have put 660 rounds, mostly ball through my new PM40. Followed Jocko's prep but am still having the slide lock open periodically. I am figuring my thumbs forward grip could be the culprit but it could be the ogive of the ammo or the mags as well. I have 3 mags, two six round and a five round. The five round has fewer occurrances but that could be due to the slight shift in grip with the six round mags. It doesn't seem to like Speer Gold dots which are my standard. The last 20 rounds were Corbon 135 grain Powerball which it seems to love. No FTF, FTE or slide locking with rounds in the mag. I have pretty big hands and thought I might be grabbing the slide lock during recoil so I attempted to modify my grip by holding the strong hand thumb down with the weak hand thumb and this helped somewhat but the slide still periodically locks open. I also fired with only my strong hand and in 50 rounds only had one incidence of the slide locking open. I also attempted simply using the weak hand to give support by gripping the wrist of the strong hand which really worked well, but still allowed a couple of cases of the slide locking back. Right now my plan is to put some more Powerball through the gun to see if it continues to feed well. If so that's what I will use. I'm also thinking of calling Kahr to see if they will send perhaps another 5 and six round mag and a new slide lock. BTW this has occurred with every type of ammo I have used, PMC and Winchester Ball and Sppeer Gold Dots, with the exception of the Powerball. Any suggestions?

gb6491
12-27-2010, 10:48 AM
Check the slide lock spring. The open end should be not be bent in towards the magazine well. If it is, carefully bend it out to a position parallel to the frame sides.
Also carefully push up on the end of the spring (mimicking the operation of the slide stop lever) while watching the length of the spring. It should not move freely about it's length when doing so; only the portion exposed to the right of the screw/washer assy. should move.
Regards,
Greg

BTW, welcome to the forums:)

jocko
12-27-2010, 11:12 AM
take the slide off, and reinsert the slide lock lever and now insert a loaded magazine with the rounds that you think are giving issues. Check to se eon the left side if those rounds are hitting that slide lock lever. That is a no no. eliminate that possability.

Ur probalbly not hitting the slide lock lever with your thumb as you are conscious of that but try shooting it left handed to see if that stops the issue. Or let another person also shoot it to eliminate that possability.



If could possably be the slide stop spring as gb6491 stated. what he is telling u is dead right. That slide stop should have zero up play in it, If it does have any uplay before you feelthe tension of that little spring wanting to keep it down, then you need to tweek that little spring with a pair of needle nose pliers, Tweek the sprng downward, not upward. That little spring is there to only keep the slide stop down, the magazine follower is what picks up the slide stop lever, nothing else comes into play. You can check allthese things out with the slide off. U can feel if that slide stop has any free play in it. That willcause premature slide locking open alot and it is very easily correctable to. There is no need to take that little screw out that holds that springhy in place to adjust it. I always put a tad bit of gun greaseon the springy tip as it just helps ride over that part of the slide stop lever that it fits into.

With the slide ont hegun andinserting the slide stop lever you should hear a snap sound , that tells you the slide stop is in properly to..

From what your telling us, to me it sounds like the rounds are hitting theinside of the sldie stop lever. For powerball to be not doing it is strange. Kahrs are not ammo sensitive, so all the brangs u listed should work to..

smokey337
12-27-2010, 12:40 PM
OK, there was a little bit of play in that slide stop. Bent the slide stop spring downward just a bit. Slide stop snaps in with an audible click and when I push up on it it now has zero play prior to feeling spring tension. Won't be able to check this out for a week but I can sure see how that might be a problem. That slide stop wouldn't have to move much for it to catch the slide. I did do a check with the speer gold dots and the nose of the bullet does, in fact, rub against the slide stop! The powerball is just slender enough to miss it. This could be a combination issue. Would a new slide stop possibly fix the problem?

jocko
12-27-2010, 01:43 PM
OK, there was a little bit of play in that slide stop. Bent the slide stop spring downward just a bit. Slide stop snaps in with an audible click and when I push up on it it now has zero play prior to feeling spring tension. Won't be able to check this out for a week but I can sure see how that might be a problem. That slide stop wouldn't have to move much for it to catch the slide. I did do a check with the speer gold dots and the nose of the bullet does, in fact, rub against the slide stop! The powerball is just slender enough to miss it. This could be a combination issue. Would a new slide stop possibly fix the problem?

call kahr and relate that tomthem. It might make a difference and it wold be cheaper for kahr to send you a slide stop to test it out than them paying to have it sent back etc. don't pay for the damn thing, . If they say they wills hip you one, then what I would do is take that side stop lever out and with a small fine file, just file a tad off where it is hitting the bullets, and then retest. Not to much or the follower willnot pick up thatslide stop leve ron the last round. Many do this also and get perfect results. Like fine tuning ur semi. Otherwise don't use that ammo that is hitting ,as u will never know if and when it is going to do it. I personaly love pwoer ballin my 9mm kahr. It feeds perfect , doesnt give issues like some can but that being said I have zero issues with any brand of ammo on my PM9.

What you have done for yourself though, it that u have just learned alot about your kahr and have learned what to do and what not to do.You might wantto review the kahr tech section and look at their lube chart it is simply the best for any semi.. If you look at your slide stop you will see that little nub that the little spring goes into andon that jub even is a slighe indentation, that is where that little spring should rest. I wen cleaning always put a dab of gun grease on that nub, . for me it just helps that spring ride over that nub and into the groove easier. That little springhy area is really a none issue if you are careful.... The manual tells u exactly how to install that slide stop lever even...

keep us posted.

I will suggest if you have not already to go to the kahr techs can see it has had over 7000 hits on it, so it is being used by many as a guide to breaking in a new gun or a used gun that one bought and knows no history of...I would like to take full credit for that thread but it is a collaboration of many excellent posts by the membership and I cannot thank them enough for it either...

jocko
12-27-2010, 01:45 PM
That little spring is easy to catch when the pistol is stripped and cleaning with a rag. I bent one on my first PM9 pistol outwards. I realized what I had done and have been careful since.

certainly make it a point to stay away from that area with a rag as u are right.... But you learned from your mistake to, so it is a no brainer from now on..:third:

what most people don't know is that this little sprighy thing is really an engineering feat. It actually does two things.

#1. If you look at your slide stop lever, up by the flat part of the lever, the round pin has a goove in it by the flat portion. This is where the back side of that little spring snaps into also. This keeps the slide stop lever from coming out of the gun. , by design

#2. That little end tip is designed to pull the slide stop lever downward all the time. If u have it in wrong, it woll pull the lever upward every time and u will gat slide lock open on every shot. That should tell you tha tyou have that little spring under that nub instead of on top of the nub. The only thibng that pushes up the slide stop lever is the magazine follower after the last round is fired. I personally like the 54% more strength magazne springs that wolffs offers for kahrs. To me it just gives that follower alittle extra ujmp on that last rond to engage the slide stop lever, for at that time the magazine spring is at its weakest strength in power and the 5t% may not sound like much and it really isn't but it helps.

That is why that little springhy has to have flesability in it or it will not work. Actually the only thing that conave washer does is hold that little springhy in place which if you hav e had it apart, u will see that one end of that spring is bent at a 90 degree which goes into a small hole in the polymer frame and as long as that washer is in place it cannot fall out our change position either. It is an engineering feat IMO, just that I would sure like to see that little screw going into some type of metal insert. and more than likely we would never be discussing this either.

smokey337
12-27-2010, 09:35 PM
Thanks Jocko

You're right! I have learned a lot about this pistol both from this forum and from my experience with it. Getting this pistol working like a fine tuned watch is becoming an obsession. I love it for carry. Just the right size.

smokey337
12-30-2010, 02:03 PM
Talked with jay at Kahr. They are sending a new slide lock. I'll let you know how it works out.