D,

There are two common types of semi conversion. Hammer fired which uses a hammer as part of the trigger group to fire the gun. It has no striker or striker spring. The striker fired semi uses a striker placed behind the carrier. It has a separate spring and is fired directly from the original Bren fire control group.

I don't know which type Len Savage builds. I doubt you are missing a spring. A weak return spring could cause the problems you are experiencing in either type of build.

Joe