TM Extended glock mags not locking back
 

So my extended mags seem to be to heavy for my TM G17. When I put the mag in, if I hold it up it will lock back, but even then the slide catch is just barely catching the slide.

My normal mags go in and my slide locks no problem....but with the extra weight of the extended ones it seems to pull it down and becomes useless.

Ive checked for wear on my mag catch and on the mags themselves but nothing is evident.

is there any fix for this?

What gun are you using? Is it a TM?

Yes, a G17

Check how far the followers come up on the side. Are they the same for both mags?

Another solution is that you can bend the slide catch down on the frame so that the mag followers press it up faster/more.

Would swapping it for a steel mag catch work better?

How old is the gun? The mag catch could be slightly worn, not enough to effect the seating of the lighter mags but noticed when using the heavier ones.
The comment about slightly bending the slide catch can solve the issue but it may not necessarily be THE solution. Altho if it's just the long mags you may as well do that until the issue presents itself with your regular mags as well.

the gun is maybe a few months old. The mag catch is steel and there is no wear evident at all. Everything looks normal and on the same level (followers ect).