Guarder recoil spring question.
 

What does the guarder recoil spring do for the glock 18c? What is the difference between the guarder and stock recoil springs?

Improves blowback speed/"crispness".

snappier return to battery with heavier metal slides. The stock spring is a little limp.

sorry to revive this old topic but I don't want to get flamed at for a topic already started. Anyways, does the Guarder Glock Recoil Spring for the g17, 18c work on the g19? All guarder glock recoil springs should be the same right?

The spring guides for the G17 and G18 are longer than the one for the G19. Guarder also makes a version for the G19, which is the same as the G23.