My 40 and 9 STI 2011 are both locking back with a 45 cal slide stop.

[lucas]

My question is, can a 9/40 slide stop work the same with a 45 STI 2011?

[ltdmstr]

If it locks back with a 45 slide stop, it will almost certainly lock back with a 9/40 slide stop, since the part that sticks into the frame to catch the follower is larger on the 9/40 version. You're going to have to modify it if you don't want it to lock back.

[jrguar]

First step is to determine what is causing it to happen. Are you bullets bumping the slide stop ? (If so you can generally polish that back to prevent it...Are you manually bumping it ? Do you have a detent in it ?

[kamikaze1a]

If you remove your slide, re-install the slide stop and then insert a loaded, partially load or empty mag you can better see how your slide stop is interacting with the follower or rounds loaded in your mag and then modify the slide stop as needed...

[lucas]

Thanks everyone, I'm making progress.

[ltdmstr]

Btw, if you put some layout fluid on the slide stop that will show exactly where the bullet is contacting it.