My AC-556 is officially a "project gun"

[SSBiggun]

I was shooting PMC 55's and had several double feeds and even live round' s ejected. I thought maybe magazine. it happened to 2 different factory Ruger 30's. the bolt would catch with the live round base above the bolt and the bullet nose part way in the chamber. I just replaced the operating spring with a new wolff spring? any thoughts.

 

[Motoquebrado]

I was having extraction/ejection and feed issues that turned out to be as a result of a worn extractor. Your issues sound a little similar, but not identical...check the extractor anyways maybe?

 

[Motoquebrado]

Also, if you have been using a Clyde SCAR stock and had issues getting a 30 round magazine out of the gun because the mag well was not properly cut out in the front of the Clyde stock, you may have broken the front magazine retainer pin which is also the rear spring guide(name)? This could be causing your magazines to not fully engage, causing fte/ftf issues. Once again, not sure, but things I've experienced.