I bought the (9mm) P11 when it first came out.
When the 40 S&W conversion came out I bought it.
Some bullet shapes would hit the slide lock and randomly lock the slide back.
I broke off the inside of the slide lock and the gun became 100% with the 40 conversion.
The slide doesn't lock back after the last round but can still be locked open manually.
I told Kel Tec what I did and they sent me a new slide lock (no charge) just in case I might want to change it out.
I use the original 9mm magazines and haven't had a single problem with them.
The 40 S&W seems hard on the aluminum receiver.
I called Kel Tec and asked them, When I shoot the gun enough that I feel the receiver isn't safe, will Kel Tec replace the receiver and how much will it cost me?
KT said, When I feel the receiver needs to be replaced, they will replace it and anything else that needs to be replaced and my cost will be Zero.
If I lost the P11 and 40 conversion, I'd be trying to buy one at the next gun show.