Specifically the bolt lock spring that is under the bolt stop when the gun is empty. Would not lock the slide back so I pulled the stop. The spring was so strong that it would not allow the stop to pop up to lock the bolt. The clip spring is plenty strong and is not the problem. I clipped a few coils off until it would catch OK but would not ride up if the gun was turned upside down. Exactly how long should the spring be? I doubt that this gun was ever used after arsenal refinishing and I paid peanuts for it. It's working fine now or so it seems but I would prefer the correct length spring.