I recently posted about a month back that my P365 (April 2018 build date) striker broke. I sent it to Sig and they replaced the striker and sent it back. I had not shot the pistol for about 4 months prior to sending it off and thus my 10 round mags were sitting loaded for that amount of time. In the meantime I bought a new 12 rounder but did not load it. After receiving the pistol back, I loaded the 12 round mag up and shot what was sitting in the 10 rounders. Both 10 rounders failed to lock the slide back, but the new 12 rounder locked it back. I loaded up all 3 mags again and noticed the 10 rounder springs were noticeably weaker than the 12 rounder. Both 10 rounders again failed to lock back. I was shooting 147 grain Federal ammo, and I am left handed, so I doubt it was the ammo or my thumbs hitting the slide stop. All mags will lock back when hand cycling on an empty magazine. I checked Wolff and they do not make P365 mag springs yet. Does anyone know of a reputable company that makes P365 mag springs yet? I would like to try some +10% mag springs and see if that fixes the issue. I’m not a big fan of Checkmate magazines, so I don’t really want to send them back to Sig if I can fix the problem correctly myself.

http://LakeLinellc.com

They have both standard and +10%

quote:

I’m not a big fan of Checkmate magazines

IMHO the problem may be the follower, not the spring.

Theres not a ton of real estate on the gun so are you perhaps riding the slide with your thumb? I wonder if so, if that might slightly slow it to not get to lock back/not give the slide stop enough room to engage.

I know I rode the slide stop alot when I had a 365 when shooting righty. Shooting lefty thats interesting. I'd say maybe ensure your thumbs are not on the slide and shoot a bunch of 1 rd mags.

Insert an empty magazine and pull the slide to the rear, if it locks back, the failures are operator induced.