HK G3, 91, PTR, CETME Extra Power Hammer Spring.New HK German extra power hammer spring For All.308/.223 Semi & Full Auto Trigger Packs.This is a must have spare replacement part for your HK firearm parts bin. The heavy hammer spring is the best solution for light primer hits, an unusually high cyclic rate, etc. This is the strongest hammer spring available for the HK 90 series of firearms.Each heavy hammer spring is the factory correct 33 lb. weight for positive detonation of even the hardest military primers commonly found in surplus ammunition. Each spring is brand new, never installed or issued. These are the last units available as they are no longer made in Germany.Fits all HK 90 series firearms, custom builds and clones.