Slide lock issues on 40 cal 2011

[Akkid17]

Thought I’d share my experience so hopefully the next person searching for this will be able to find it easier. 
I was having an issue with a 40 cal 2011 locking back early with mostly full mags. I was having the issue with several types of bullets (2 different JHP’s, coated RNFP, and FMJ)  and different overall lengths (from 1.135”-1.200”) as well as 4 different mags all with either brand new or relatively fresh springs (gen 1 and 2 STI, atlas and MBX mags, all of the STI mags were running grams spring and follower)

 

The gun would lock back randomly with varying amounts of ammo still in the mags and would do so with several different bullet and mag combinations. The culprit was the bullets shifting forward in the mag and the ogive of the bullet lifting the slide stop. 
 

To check this I pulled the slide off the frame and reinstalled the slide stop. Then tried a couple mags and bullets to see what was happening. In the pics you can see how close the bullets are to the slide stop and when I tapped them to the front of the mag and reinserted the mag the slide stop would lift. 
 

 

[Akkid17]

I found a couple of options to fix this:

1) Grinding down the slide stop so it would not longer be able to contact the bullets and potentially the portion of the follower that engages the slide stop. 
 

2) Drilling a recess/divot in the location that the frame detent interacts with the slide stop increasing the resistance required to activate it. 
 

I have tried option 1 before and it made it to where the bullets wouldn’t engage the slide too early but the followers wouldn’t engage it either. While this was the goal of the previous gun I wanted to keep the functionality on this pistol to see how it would work.

 

I wound up doing both and it seems to be working great, I removed a little more than needed but it will still lock back on an empty mag if the follower has the slide lock tab still in tact. Put around 350 rounds through it using various combinations and the only stoppages were due to nose dives on the short ammo in the gen 2 STI mags.  
 

If I were to try again I may see what just drilling a divot would do since it did dramatically increased the force required to activate the slide stop.