Back in the day when I shot an M-14 in service rifle competition I could get new173 gr M118 FMJ projectiles in bulk through DCM and they shot nearly as well as 168 gr BTHP MKs. They made great practice ammunition and my handloads with them were usually more accurate than issued M852 match ammuniiton using the sierra 168gr BTHP - but that was due to the custom nature of the load, not the bullet.
I tried M80 bullets and they were shootable but not capable of nearly the same level of accuracy as the 173 gr M118 or 168 gr Sierra.
WIth any FMJ round, the open base creates greater potential for inconsistency, and consistency of the base is vital for accuracy. And since the demise of the M-14 as a standard infantry rifle, the M80 round was primarily intended for use in machine guns where pin point accuracy is not required - or even desired as it is an area weapon where some dispersion can be desireable.