.40 S&W mags not interchangeable

[at_liberty]

When in the car, I have a PM40 in a fanny pack and a T40 behind me on my belt, where it is not realistic to consider it accessible. It is covered and more or less tangled up in seat belt and concealment clothing.

One factor in selecting the PM40 was the concept of sharing ammo. I wondered whether I could also use the T40 spare mag as the spare for the PM40, although obviously the 7 round mag would extend quite a bit on the PM40. I tried it, and the mag goes in and clicks fine, but the round won't load. The slide won't move. It's all jammed, until I drop the mag by pulling it out...kind of awkward and dangerous.

I wanted to avoid the extra weight of a spare mag in the fanny pack. I already stopped carrying my phone in it. I probably won't carry the extra mag. When able to use my shoulder holster in colder weather, the PM40 system is all self contained with two spare mags. The main factor then is finding coats and jackets with either button fronts or with two way zippers, allowing quick access to my shoulder holster...or any for that matter.

In my State (SC) the gun has to be on your body or completely stashed when in a vehicle. There are no options for a weapon at the ready somewhere else in the vehicle, stuck between or under seats, etc.

The point of my post is to either establish that .40 S&W mags are not necessarily interchangeable among models, or to solicit information that solves the problem. Frankly, I am really disappointed and may replace the whole system.

I must admit that where I am at with it right now is no different than carrying a 5 shot revolver as a backup, most likely a S&W 642. At 5+1 with the PM40, I am actually a little better off, assuming everything cycles okay when needed. Comments welcome.

[ripley16]

Bummer... I too assumed that the mags of common caliber fit all the models of that caliber. The only one's I've confirmed have compatability are T and TP 9mm fit in K, P and CW 9mm models.

[Frankhenrylee]

How many rounds have you put through your PM40? Mine had a little trouble at first but after 250 rds. it works, haven't tried with that mag though.

[at_liberty]

How many rounds have you put through your PM40? Mine had a little trouble at first but after 250 rds. it works, haven't tried with that mag though.

I wonder if you misunderstand. The PM40 was bought used and has been functioning perfectly, well broken in. The whole point is whether the 7 round T40 mag works in the shorter grip PM40. I certainly concluded that it did not work in the smaller PM40.

I will note that I did not ram the mag in particularly and that I tried it more than once with the same result.

[Frankhenrylee]

You wonder correctly. I'm afraid I have no advice if its not a break in issue. I'm sure it won't be long before somebody chimes in with something definitive.

[gb6491]

Hmm....something amiss here, the Kahr Store lists the K40 7 rd.magazine as:
K40 Magazine, 7 Rd. (http://www.kahrshop.com/cgi-bin/itemdetail.asp?itmid=1025)
(Fits T40, TP40, K40, K40Covert, CW40, P40, P40 Covert, MK40 and PM40)

it might be time to query the mothership as to why your seven rounder doesn't work in your PM (perhaps a swap out of magazines is in order).

Regards,
Greg

[at_liberty]

Hmm....something amiss here, the Kahr Store lists the K40 7 rd.magazine as:
K40 Magazine, 7 Rd. (http://www.kahrshop.com/cgi-bin/itemdetail.asp?itmid=1025)
(Fits T40, TP40, K40, K40Covert, CW40, P40, P40 Covert, MK40 and PM40)

it might be time to query the mothership as to why your seven rounder doesn't work in your PM (perhaps a swap out of magazines is in order).

Regards,
Greg

Okay...on the tip that it should work, I took another pass at it. I found that the slide would feed manually with the longer mags. A pretty good shove, and the round would load. That was not necessary on the short, flush-fitting mag (5 round). I tried both the Speer Gold Dot carry ammo and a semi-wad cutter (flat nose) range ammo.

I examined the ramp under magnification. It looked well worn but completely dry. I swabbed the ramp and feed area with a wool dauber impregnated with Break-Free. The fully loaded, extended grip mag loaded perfectly on the first attempt, requiring no coaxing. So, I guess the ramp was too dry or needs to be polished. I don't normally lube in the ammo area, so I will talk to a gunsmith about ramp polishing.

There is still the fact that the shorter mag never had a problem.

So, you guys did solve another one. Nice going. Many thanks.

[ripley16]

I've been thinking about this.. Because you said the gun was used, with an unknown round count, perhaps the slide not being able to easily strip off a round is an indicator that the recoil spring needs replacing. Maybe it can't cope with the little bit of extra pressure the longer mag spring exerts. Just thinking outloud...

[Bawanna]

I've been thinking about this.. Because you said the gun was used, with an unknown round count, perhaps the slide not being able to easily strip off a round is an indicator that the recoil spring needs replacing. Maybe it can't cope with the little bit of extra pressure the longer mag spring exerts. Just thinking outloud...

Perhaps a good think out loud too. Could be a contributing factor. Since the flush mags work and the extended don't your idea along with maybe a tiny bit of difference in feed orientation that was cured with a dab of oil means the issue might not be to huge.
At Liberty, in your spot I'd break out the dremel tool and put a little polish on that ramp yourself. A polishing wheel with a bit of polishing compound or flitz or your wifes silver polish (not too familiar with this one, silver? yeah right) but it'll all work. You can't hurt anything polishing within reason. If your seeing sparks, your no longer polishing your grinding and you can damage alot. Nothing hard about it. Order up a recoil spring, shine that ramp and let us all know how things are in your world.

[at_liberty]

I have polished the ramp but haven't been to the range yet. So far, it works fine when manually racking the slide on the first round...either length magazine. That's an improvement.

A variable I didn't mention, brought to mind by the idea that the recoil spring may not have enough juice to run the longer magazine, that mag has a new +5% Wolff spring in it, addressing the earlier problem on its T40 home. There should definitely be a difference in how much the two mags retain their tightest first rounds. I will see how the thing operates at the range before considering a new recoil spring. I think the first round is going to load, so that part is probably okay.

Before polishing the ramp, I noticed under magnification that the grinding of the concave surface was more coarse than on my T40 barrel. When ground in a circular motion, that leaves a perpendicular, washboard surface that the loading bullet tip has to overcome. I have a 3/8" diameter honing stone for my knives, a good fit for that ramp hollow, so I worked that rounded surface vertically until most of the horizontal grit lines were barely visible, thinking in terms of microscopic differences. I then polished with the Dremel felt wheel and some MAAS cream, and the thing looks like jewelry.

I lightly wiped with BreakFree CLP. The gun immediately accepted the first round perfectly, using either the 7 round or 5 round mag. I expect it will shoot fine, but we'll see.

'Appreciate all the good ideas.

[Bawanna]

I had a little bit of the same washboard effect on the MK9 I polished this morning. I was afraid of the stone in the dremel so I went with some fine emery cloth and a small dowel. It seemed to help some, perhaps not perfect but a large improvement. It had no issues to cure but this should make it just that much better.

[at_liberty]

Range report on the PM40 that was not loading from a longer T40 mag (7 round instead of 5). The ramp had been polished and the gun was loading when manually racked.

The report is that the gun isn't working right, usually but not always jamming on the nose-down first round off the longer mag with new +5% spring.

I discovered that the front part of the follower was broken and riding inside the 5 round mag. The mag was still working fine. I replaced the follower but the point is that in the process noticed that the short mags spring tension is far below that of the 7 round, T40 mag. I know well, because putting in new +5% springs was quite an ordeal. I am not sure what I will do about wanting to use T40 mag on my belt as a backup for the PM40 fanny pack gun. I will at least get some new springs on order for the 5 round mags.

I have another issue now and that is the gun does not want to drop short mags. I have to press the mag release deeply to get it to release. It is not that the mag won't pop out once released, although I would like a more positive spring action, now expected from installing new mag springs.

The type of .40 S&W ammo that was jamming, found not having taken a good angle to go up the ramp (to the chamber), was the flat nose FMJ, Speer Gold Dot HP, and Federal Hydra-Shock HP. It hits the ramp and stops.

Those are all the observations and possible hints I can think of. Troubleshooting ideas or general advice is welcome.

[at_liberty]

Re the well used PM40 that was not loading from longer T40 mags, I received the new mag springs, followers, and recoil spring assembly today. I installed everything and it didn't make any difference. I can get the round to feed if I wiggle the protruding end of the mag around a bit. I concluded that the longer mag goes in a bit farther. On the 5 round mag, it goes flush before being inserted too far. On the extended grip 6 round mag, the grip extension stops the mag from going in too far. On the 7 round mag, if I ram it too much, it goes in just a grunt too far. I think that might mean there is wear on the polymer mag release, if that is what is really controlling the amount of insertion. I was not satisfied with the way it was dropping mags anyway. With a good LED light in the mag well I can see that the mag release looks pretty good, better than I expected.

I don't know how to disassemble the frame enough to install a new mag release. What should I do?

A side note, the recoil spring assembly had a larger diameter base disc than the original. I did specify "old style" slide. The polymer frame has a molded pocket big enough to accept the larger diameter, but it took some fiddling to get the gun to go back together. The disc did not want to go into that pocket in the frame.

I will be shooting it later today to prove it all out.

[at_liberty]

Did some range tests last night and got some help from one of the experts, who also test fired the gun. Turns out that he had zero problems with either mag (std 5 or the T40's 7 round) using smooth nose ammo. I was always testing my carry mags with hollow points loaded. He suggested I try various defensive ammo to see what the gun likes. I actually have some Hornady, which I haven't tried yet.

He suggested further polishing of the ramp and chamber too, using the bullet shaped Dremel polisher attachment. I think the implication there was that it might make the gun less temperamental about which ammo I used.

His verdict was that the gun works while the new recoil springs need some break in. He was able to lock the slide without an empty clip but I couldn't do it.

[at_liberty]

I put the original recoil spring assembly back in and now I can lock the slide with no mag. After getting over a hundred dollars worth of parts I ended up using only the mag springs. Everything I got was marked as 9mm parts, supposedly interchangeable, I guess, but none of it worked entirely. Nothing was the actual part number I ordered. I counted coils on the springs, and they are not the same. Using a new spring might require some break in, but I need to be able to lock the slide open. I couldn't even force it but I watched a bigger, stronger man do it. Of course the old spring feels like butter, and everything is easy to operate. As long as the slide closes okay when chambering a round, I am not swapping out anything.

[wyntrout]

It's easier to lock the slide back if you bring both hands close to your chest and even anchor one there while pushing together with both hands. For me, I anchor my right hand with the wrist on my chest, thumb ready to push the slide lock into place while gripping the slide from the top with my thumb along the slide over the serrations and pushing it to the rear until I can thumb up the lock with my gun hand. I can get more strength in pushing both hands together that way.
Wynn

[jocko]

LIBERTY: Alittle tip for reinstalling those magazine springs be they the factory or the 5% more strength ones. push the springi n as far as you can with your finger and then slide a nail through that last hole in the side of the magazine. It will hold that spring in place and then you can easily install the mag inner plate and bottom floor plate.

Your recoil assembly that they sent you is perfectly ok today. Kahr a few eyars back went fromt he 3/8" flat end peace on the recoil assembly to the now 1/2" size. Why I cannot tell you but I know it effects nothing and u are better off with the 1/2" size or they would not have made that change.

I personally have no issues that my magazines don't fall free out of my pM9. I don't carry a spare anyhow and I don't worry about accidentely hitting that mag button and having that magazine fly out all over the place either. You can get very fast in changing magazines either way.

If the magazine release button is working ok, don't mess with it, I don't think that will help your free flying magazines anyhow.

Some one on this forum posted a super nice photo/essay of how to change the magazine release. I do not remember who it was, maybe they will read this and put it up again. We asked for it to be a sticky, for it was just that good but it never made it that far. It is a no brainer to change that mag release but IMO, if it ain't broke, don't fix it.

sounds like your getting the quirks out of the gun to. A wise move IMO to let another qualifed person shoot your gun. When they can do it properly and you can't it tend sto show that it is not gun related..

[at_liberty]

I think the verdict is in here after a range visit today. If I dump the Federal HydraShock and Speer Gold Dots that run fine in the T40 and load all Hornady 180 gr XTP in both the PM40 and T40, the PM40 will take the ammo from the T40 mags just fine. The Hornady bullet nose is smoother, meant to run better in guns made to favor round ball ammo. The hollow point opening is smaller.

Recall that the goal was to be able to use the T40 belt mag as a possible reload for the PM40 fanny pack gun (sitting in the car). Used in the PM40, I was having consistent FTF off the 7 round mags, which have new +5% springs.

Now I have to load it favoring the PM40, which is cool. The Hornady ammo is awesome anyway, and I get to shoot up some premium, rock 'em-sock 'em defensive ammo in my T40. I have about 36 rounds (of Speer and Federal). This older stuff is supersonic, so the experience is different than 180 gr practice rounds with conservative loads. Maybe I'll try it at greater range, say 15 yards. I will use ear plugs inside my headset. I do that consistently now, so my ears don't ring as much when I get home. Inevitably, some guy will be shooting some movie gun nearby, and the whole building shakes when it goes off.

[jlottmc]

Whats wrong with a cannon? All things considered I think you'll be quite happy with the Hornady ammo. That's one of the things about auto's, sometimes you have to find the right ammo.