Are you having weak blowback?
Are you having low fps?
This is a very common problem among glock users who have a poor seal between the gas route and the air nozzle regardless if they have upgraded to the Nineball gas route for their magazines. A lot of individuals shim or increase the height of their gas route using various methods for all their mags. Instead of modding all my mags, I decided to mod my air nozzles instead.
I simply used cyanoacrylic glue (ie. super glue) and accelerator to cure the glue instantly. Surrounding the opening of the air nozzle is a small rectangular recess that conforms with the shape of the gas route. I simply filled the recess with cyanoacrylic glue to build up the height and cured it instantly using the accelerator. Simply use the 400-800 grit sandpaper and sand it down to create a smoother surface at the desired height. Make sure that it is not too high though or else it will impede cycling. (For WE M4/416/SCAR/PDW users, you can perform this mod too if you experience poor seal). If you still experience poor blow back and low fps, try using a larger piston head O-ring (the WE piston lids are slightly larger in diameter and can form a better seal with TM style air nozzles).
After performing this mod with two of my glocks, I gained 10-15fps, my slide locks back more consistently, and my blowback was much stronger! The good thing about this mod is that it is modular- you can sand down the glue as much as you want to the desired height, or you can simply use an exacto knife to pry it off completely. Here are some pictures:
Here is a sneak peak of my duracoated (slide only) FDE TM G17 with custom stippling by me
