Failure to fire issue

[CrossedCannons]

check the cutout in the receiver for the firing pin too, may be "burred"?

[Bruce McAskill]

Have you checked the area of the receiver where the bolt locks up when it's forward. Where the back side of the lugs sits against the receiver. Is there any Duracoat in there? If so remove it. It maybe slowing the bolt down not allowing it to lock up properly. The other may be the recoil spring. Do you still have the original? If so replace the new Wolff spring with the original as some Wolff recoil springs are known to create problems. The so called Hi-speed ones are not very good.