Looking at Springfield M1A's, Sig. 716, SCAR 17s, FN FAL and Ruger sr 762.
Out of those you have listed I'd pick the FAL. It's battle tested, accurate, ergonomics are good and parts and mags are common and are fairly affordable (not as affordable as the dirt cheap H&K G3 parts and mags, but okay). Buying good quality ammo is a goal we should all aspire to, but if the various panics have taught me anything it's that good quality ammo might not be around unless it's already stored in your closet.
Back to the rifles though.
• The assorted manufacturers of the various .308 AR-10's can't even get it together and come to some sort of agreement upon which mags to use, much less parts.
Besides the RRA LAR-8 that I used to own (bought it from my father-in-law to try out, used it for a few hogs, some target shooting and a mini torture test) the .308 AR's I've had the most contact with have been the DPMS and then the Armalite. My friends and family who've gone with the DPMS haven't had very good luck at all. The ones I've seen and shot if run dirty and used hard they'll start to stutter and they've occasionally broken (the firing pins, extractors and then their pins seem particularly prone towards breakage). Never had that issue with the FAL's, the M1A, the H&K/PTR's, the BM-59 or the .308 Garands I own or have owned.
The Armalites seem to be a mixed bag. Some are amazingly reliable and others not so much. Mags on the Armalite are overpriced though.
The shooters that seem to have had the most success are the ones who are testing it from their closet (meaning they aren't shooting them much) or who are using it for hunting. Going to the range or deer lease, shooting a few boxes prior to going out, shooting several hogs or a deer, cleaning it and then back into the closet it goes. That's how I used that LAR-8 for the most part.
I haven't tried or owned one of the LMT's, the La Rue's or the Noveske's .308 AR's. Maybe you have to go with something like that if you expect it to run well despite being rode hard and put up wet.
• The SCAR 17s are unreasonably expensive, same goes for their mags and parts. Seriously. $2500 to $3000 just buys you the rifle. It's barrel assembly (to change out the barrel) is $999 to $1279. Buying a lot of 4 SCAR 17 mags and you're looking at $164.99 (New FAL mags are $18-20 a pop, new in wrapper H&K surplus G3 mags are $3 a pop...no, that's not a typo, $3/three dollars per magazine). Forget all that. It's not really my way to bag on the purchases made by friends, so I just told my buddy that it was very nice but that I didn't feel that it was worth the money. For that amount of money he could have gotten an FAL and a Trijicon TA-11.
• The Sig 716 is nice, but with the FAL from DSA being several hundred dollars less in price there's not much point in getting one of those instead of an FAL.
• The Springfield M1A is the other alternative to the FAL and I liked mine, very accurate. The mags cost a bit more though. To me the ergonomics of the M1A aren't quite as good as with the FAL and scoping it made the package feel awkward. So out of the two I'd still go FAL, it's still a good rifle though.
• Don't know anything about the Ruger SR-762, so I can't say much about it. All the other .308 semi options that are out there I either own or have owned in the past (DSA and Imbel FAL's, H&K 91, JLD PTR-91, Springfield M1A, Beretta BM-59, RRA LAR-8, Tanker Garand) or at least shot a fair number of times (Sig 716 and the SCAR 17s). Can't say the same about the Ruger. They aren't that popular in Texas I guess, only ever seen one in a shop once.
So out of your list I'd definitely go with an FAL (DSA, my IMBEL while reliable had some vertical stringing) and if you were looking at the SCAR 17s and have the money I'd also get a TA-11 ACOG, 20+ mags, several thousand rds and a rifle class to go wring it out.