The mag not locking back: do you shoot with a high thumbs grip? It is possible that you are inadvertently tripping the slide release. I believe others have reported this happens with their P239's, but not their other SIGs. Must be something in the design of the mag release, or the grip.
I don't have that issue, but I don't ride my thumbs high.
My P239 needs no more cleaning than any other pistol I've owned, so unless yours is VERY dirty I don't think that's it. I do clean after every range session, but I'm not a perfectionist.
I do, however, clean under the
extractor lip every time I clean my guns; for me, that means taking a patch wet with Hoppe's, doubling it over, and using a straightened paperclip to push it under the claw. Just a habit I garnered from a picky 1911.
In other news... The Nill grips are
superb on the P239. I am so happy I waited to find a pair. They fit my hand beautifully, and make the grip fill the hand a little better. The balance of the gun feels so much better with the Nill's. I shoot a little better with them. My only reservation with them is they feel a little dry... Do they need regular oiling? I'll let everyone know how they hold up to a summer of carrying.
P228 and Action Package: I'm not thrilled. The trigger is nice, but how much nicer than before I spent the $150? Not much. Maybe a tad smoother in DA, but it was never rough to start with. Honestly it just feels like the trigger group was cleaned and lubed... Not real appreciable change in action. I'm pretty disappointed, to tell you the truth.
That said, the P228 is a wonder. I am so glad I grabbed that gun. 1993 W German vintage, tight as a duck's butt (unlike my P239!) and a natural shooter. I really like that gun, and it deserves some Nill's, too. I like the nitron'd slide, although I can see some gloss differential when holding it in the light. I hope that's not a thin application, just a remnant of SIG's stripping of the slide (it was blued, of course). I know some aren't hot on nitron, but I like the way it looks, and the price was right since the gun was already back at SIG getting the SSP.
SSP: well worth it. SIG did a great job detail stripping, and of course the new nites are great. A sweet deal, even at the new price of $129. I do wish they would have put in new magazine springs, but I guess I could buy those on my own