If you knew your weapon and the various sights settings, getting solid hits at 5-600 meters was routine on "man-sized targets".
As far as weight goes, I am medium height, medium build and I sort of grew into the the rifle. I had a buddy who was with the 82nd Airborne in Vietnam and he told me that "the M16 was the right rifle for Vietnam because it was light, handy and they could carry much more ammo -and the M4 was too heavy". I told him that "I wish you had told me - I would have sent a big, strong Marine to hold your rifle up for you". He wasn't amused.
When our battalion converted to the M16 in March 1967, I held on to my '14 and watched the disaster with the M16 happen around me - guys dead by their torn-down M16s. My Company commander asked me why I still carried an M14 and I told him that "I'm in artillery and we don't have the M16 yet" so he told me to "get one as soon as they do". Then when I'd go back to my parent battery for my mail, they say "Chainmail - your M16 is in the armory" and I'd tell them "the grunts want me to keep my M14".
I kept that rifle the whole 17 months I was in Vietnam and I'm alive because I had it.
When I was commissioned a lieutenant in '73 I was volunteered for the Rifle and Pistol Team and won some matches and some shooting competitions up till I made Major and I had to choose between being a full-time competitor of move on in may artillery career. I chose artillery.
I still have an "M1A" (Devine Texas) and it still feels right in my hands.
That's because it's almost the same gun. Most of the parts will interchange. Springfield claims their standard M1a's will shoot either 7.62x51 or .308win. All standard rifles and National Match rifles out of the box that I ever shot liked the 7.62x51 better. They shot M80 OK but M118LR shot the best. You can still get that ammo online if you look. Hang on to that rifle. The way things are going, you may need it. The gun-grabbers will be looking for all those "mean-looking" AR10 and AR15 rifles first. They never give those wooden stock M14 or M1a guns a second look. That will be their mistake. Mine's in the safe with a stack of magazines ready to go. Happy trails, buddy.