Most civilian production 308 rounds have failure to feed issues, looks like the bolt isn't moving far enough back to cleanly eject, 3-4 per magazine.
Those are two different issues,
some questions...
1) what is "most civilian ammo"?? Meaning, what brands/loads have you tried?
2) What is "cleanly eject"?? Cases are extracted but not ejected?? Does the rifle jam with a fired case in the action? Something else???
To be clear, extraction / ejection problems can result in feeding problems, but you can't have a "feeding problem" until you have finished the ejection cycle without issues.
3) specifically, what is your "M14style" semi auto rifle?? Make/model...?
If you are over gassing your rifle, the bolt may move faster than designed. That, in turn, can lead to a number of problems,
It is extremely difficult to "overgas" an M14/M1A. Unlike the direct impingement system of an AR, and even unlike the GI piston system of an M1 Garand, the M14 piston system is "self regulating". What this means is, essentially, that when the piston starts to move, additional gas pressure from the barrel is cut off, and dumped outside.
Based on what you've told us, I'd agree the most likely thing is short stroking. Clean the gas system, reassemble properly, and don't oil it. That's a first step, and may be all that is needed.
IF you don't have the manual for your rifle, get one. Clean and properly lube the rifle and try again, If you still have a problem, pay close attention to exactly what is happening, and when. Come back with that info and we can try to help figure it out.