I am having an issue with my CETME's firing pin spring. The one I got with the rifle seems to be to light and doesn't hold the firing pin back creating a slam fire situation. I got a new spring and this spring is much heavier. When you shoot the rifle the bolt stays back. Got the replacement spring from HK Parts. Replacement Spring is a lot heavier than the one that was in the gun. Put the old spring back in and the gun cycles but doesn't hold the firing pin back and then creates the slam fire. The new spring will not let the bolt cock and bolt stays back. Bolt hangs back and if you clear the weapon and hit the butstock on the ground. The bolt releases and cycles forward. Do they make different weight springs? Any thoughts would be appreciated.