Yup, the softer Federal primers will slamfire , especially if you DO NOT load it from the magazine. :roll:
Use your magazine to load the Federal rounds or ANY cartridges into your M14 / M1A chamber. If you are at a range , benchresting your rifle, I like to load the nose of the bullet almost on the edge of the chamber ready for the trip forward. :mrgreen: Then Ill ensure the base of the cartridge under the right lip of the magazine. :roll: Then yank or slap that op rod handle rearwards and let the op rod fly forward. 8)
Enjoy the M14 "music". It's my favourite sound. :wink:
Hope this helps you avoid slamfires.
Barney