The spring is easy to check but maybe even easier to just replace. The benefit of checking it is that if it's tired and too light, it would give confidence that it was the issue. Cheap and easy either way. I've slacked lately with so little time but I try to simply replace them every other year in all of my br rifles. Been down the path of trying to diagnose it not shooting right and it's just not worth it so a fp spring is now a maintenance item to me. Preventative maintenance. Really nothing more nor less. Still betting yours needs bushed but this eliminates one thing...easily. Ignition is so critical and going bang does not mean it has proper ignition. In most cases, I go back with the original spring as opposed to extra power versions, etcDropped gun off at Gunsmiths shop for evaluation. He is going to talk to Kelby's & atleast replace the bolt spring.
Thank you for everyones input.