Get the specs on your recoil system up here first. Internal length of the receiver extension - internal length, the depth of the tube - buffer length (and weight, if known), and the spring dimensions (relaxed length, coil count, wire diameter if possible).
Gotta start there.
Double feeds. Just a word on those. They are commonly misdiagnosed. If you have a true double feed (two live rounds trying to enter the chamber at the same time), it is ALWAYS mag related. Always.