Need help figuring out why my model 64 is having a FTF issue?

My model 64 has been flawless since the purchase of it a few years back. With around 4000 rounds through it now it's starting to have Fell to fire issue's. I've tried different brands of ammo without any luck and have given it a good cleaning a few time's here lately. My question is, could it be the firing pin and can you change to hammer & bolt spring on the bolt? I notice that it's connected to the bolt and when I've cleaned the rifle I haven't figure out how to remove the springs from the bolt.
Any help would be appreciated - Brad

Maybe either a worn out firing pin or the bolt spring isn't keeping the bolt all the way foward when it closes. The bolt retainer and springs are held in place by a splined pin that is pressed into the bolt.