Is there a way to make the glock abit heavier like some sort of putty or sealant to add abit of weight to it?
Pull it apart and glue in sponge bits of metal, or use epoxy etc
Use fishing sinkers in any spare space there is.
Have a look at this post by @Sam_D
The stick on wheel weights are best… cut them singular or fit them in strips… wherever there is room inside for them
I bought a roll of these and stick them inside blasters… and make my RC excavators and other stuff heavier as counterweights… they fit in anywhere