I own two Kel-Tec P-40's and am quite impressed with them. If you have one that you've given up on, try a few of these suggestions.
1) Don't use 180 grain ammo. My best ammo choices are 135 grain Hydrashok, 135 grain Cor Bon, and 155 grain Gold Dot. The Hydrashoks are the easiest to shoot, and feel very similar to shooting a 9mm P-11 with Win Value ammo. I'm now using the Cor Bons for carry and 165 grain Win Value for practice.
2) Check your mags. There are two editions of the P-40 mags. The older one has a mag release slot on both sides. The newer ones only have one mag release slot on the right side. You want the newer one. Return it to Kel-Tec for an exchange if you have the older one because the mag lip cutouts are different.
3) Don't buy the +1 finger rest extension. The appeal of having 10 rounds is not worth the aggravation of having the first round jam low into the feed ramp. It will cause dangerous bullet setback. If you want a finger rest buy the one made for the P-11. You won't get the extra round, but you will still have a functioning mag. The +1 extension was not designed large enough to fit the extra round properly. When the first round strips off it will be pushed out of the mag at a downward angle. This will cause it to impact hard on the feed ramp, or even miss the feed ramp low, hitting the frame. If your +1 extension works I'm happy for you. I have three that are useless.
4) There is another common mag problem. The last two rounds will quite often feed so that they wind up sticking straight up, jamming between the slide and the barrel. The problem here is the follower and the way it rests on the mag spring as it comes from the factory. In an attempt to cure the low first round feeding problem the mags ship with half of the top mag spring coil bent upward at a 45 degree angle. You will see it immediately when you take out the spring. Flattening out this angle will in most cases stop the last two rounds from coming out straight up. A better solution is to buy Wolff replacement mag springs. They do not have this upward bend, and the extra power will help you get more reliable feeding. BTW, I have never had a malfunction using P-11 mags in the P-40. You only get 8 round capacity, but the follower in the P-11 has those long legs (to make it 10 round capacity instead of 12) attached to it that assures you that the round will always strip off at a perfect angle. I've tested them with several hundred rounds.
5) Polish the feed ramp. Some older Kel-Tec barrels have very rough machining marks on them, sort of like a washboard when you look at them closely. Some 600 grit sandpaper will polish out the rough spots.
6) Use some type of grip sleeve like the Hogue Handall Jr., which I have on both of mine. A good grip is essential to proper functioning. The finger rest extension also helps.
I have both of my P-40's working perfectly now, and they are both extremely accurate for me out to 21 feet, which is fine for self defense. The last time I checked, Kel-Tec still has some .357 SIG barrels for about $129.00. The Kel-Tec hard chrome slide exchange is still available for $20.00. I exchanged both of my slides for hard chrome. I also have the ungrooved trigger shoes installed.
Here's a pic from when I still had the +1 finger extension. I'm using the P-11 finger rest now.
Best regards, Keys
1) Don't use 180 grain ammo. My best ammo choices are 135 grain Hydrashok, 135 grain Cor Bon, and 155 grain Gold Dot. The Hydrashoks are the easiest to shoot, and feel very similar to shooting a 9mm P-11 with Win Value ammo. I'm now using the Cor Bons for carry and 165 grain Win Value for practice.
2) Check your mags. There are two editions of the P-40 mags. The older one has a mag release slot on both sides. The newer ones only have one mag release slot on the right side. You want the newer one. Return it to Kel-Tec for an exchange if you have the older one because the mag lip cutouts are different.
3) Don't buy the +1 finger rest extension. The appeal of having 10 rounds is not worth the aggravation of having the first round jam low into the feed ramp. It will cause dangerous bullet setback. If you want a finger rest buy the one made for the P-11. You won't get the extra round, but you will still have a functioning mag. The +1 extension was not designed large enough to fit the extra round properly. When the first round strips off it will be pushed out of the mag at a downward angle. This will cause it to impact hard on the feed ramp, or even miss the feed ramp low, hitting the frame. If your +1 extension works I'm happy for you. I have three that are useless.
4) There is another common mag problem. The last two rounds will quite often feed so that they wind up sticking straight up, jamming between the slide and the barrel. The problem here is the follower and the way it rests on the mag spring as it comes from the factory. In an attempt to cure the low first round feeding problem the mags ship with half of the top mag spring coil bent upward at a 45 degree angle. You will see it immediately when you take out the spring. Flattening out this angle will in most cases stop the last two rounds from coming out straight up. A better solution is to buy Wolff replacement mag springs. They do not have this upward bend, and the extra power will help you get more reliable feeding. BTW, I have never had a malfunction using P-11 mags in the P-40. You only get 8 round capacity, but the follower in the P-11 has those long legs (to make it 10 round capacity instead of 12) attached to it that assures you that the round will always strip off at a perfect angle. I've tested them with several hundred rounds.
5) Polish the feed ramp. Some older Kel-Tec barrels have very rough machining marks on them, sort of like a washboard when you look at them closely. Some 600 grit sandpaper will polish out the rough spots.
6) Use some type of grip sleeve like the Hogue Handall Jr., which I have on both of mine. A good grip is essential to proper functioning. The finger rest extension also helps.
I have both of my P-40's working perfectly now, and they are both extremely accurate for me out to 21 feet, which is fine for self defense. The last time I checked, Kel-Tec still has some .357 SIG barrels for about $129.00. The Kel-Tec hard chrome slide exchange is still available for $20.00. I exchanged both of my slides for hard chrome. I also have the ungrooved trigger shoes installed.
Here's a pic from when I still had the +1 finger extension. I'm using the P-11 finger rest now.
Best regards, Keys
). I have proven the reliability of my Kel-Tecs through extensive range testing. 
