Slide not locking on empty mag.Thoughts?

[carlt]

Hey for some odd reason my MP9 slide did not lock after an empty mag. Any idea whats causing this?

 

[carlt]

Hey for some odd reason my MP9 slide did not lock after an empty mag. Any idea whats causing this?

 

[pberry]

My first thought would be mag follower not coming all the way up. You might clean the mag and see if that helps.
Phil

 

[CTPete]

Chances are you need to replace the mag spring.

 

[gmchenry]

Thumb making contact with the slide stop?

 

[Matt Murphy]

If it's not staying open on only certain mags, it's the followers. Mark the magazines and keep track of which ones it's happening with. S&W will probably send you a new magazine, don't know if they'll want the old one back or not.

 

[handgunner356]

Will it lock on a empty mag if you pull the slide back by hand? If it does then your mag is OK. Your load might not be hot enough to fully cycle the slide to engage it.

 

[ShelbyV8]

Low power ammo and limp wristing can cause the problem with poly pistols.

 

[carlt]

At the range I use Winchester 115 gr FMJ rounds, most agree that's typical for the range, so I'm a doubtful it that. When handling my firearm I do it with authority (very tight grip). Now I must admit I have to revisit my thumbs disengaging the slide. I really don't think that's it but I'll have to see.