Not sure of your intended roll for either a M-14 or some form of Stoner type 7.62, so reliable can mean a lot of things. Some of the most reliable firearms ever built, within the minds of some, are designated "queens" that reside in a near permanent resting place inside the owner's safe. The only hard use these firearms see, are played out in the mind of said owner.
I'll carry a truck load of love for the M14 to my grave, and they continue to this day to find a way onto the battlefield in some limited capacity and roll as a designated marksman rifle. It is long gone, however, and has been greatly surpassed, within the capacity and roll as a combat service rifle.
The later improvements made by Stoner on his platform, and the subsequent variations of such a semi-auto 7.62 in the numerous packages, have nearly overtaken not only the roll of sniper packages, but are now taking over the roll of designated marksman rifle with more compact and lighter close quarter packages of the same platform. I believe H&K just won a contract for such a package of their platform to be used in such a roll to support the M110 sniper. So in that context, the old M14 is ancient stuff that sees limited use in various unique packages made up from mothballed rifles.
If looking for a reliable combat service rifle, you will likely never see a newer variation of a Stoner 7.62, as it would be too heavy. For the same token, that is why the M14 is no longer considered a good choice as a reliable combat service rifle, it is too darn heavy, in both rifle and in ammunition. The M16 platform, with all of its improvements, is a better choice for that roll. And as far as the later improvements made by Stoner for his 7.62 platform, these improvements were carried over by KAC to the M16 platform, to address all the common malfunctions identified by the military, and these Stoner rifle improvements have either greatly reduced or completely eliminated every identified problem on the list. So this very latest E-3 Mod2 package has taken the M16 platform, with all its differing packages, to a level of performance far exceeding levels of the past. You cannot reach such a level of combat service rifle performance with an M14, in any package.
So with all that said, if you have money burning a hole in your pocket, get any darn thing you please. If it is a safe queen, it will last a very long time. If you get a solid rack grade civilian version of the M14, or any civilian copy of a designated marksman package, they are a lot of fun and are rather cool to have. But, the "AR type" 7.62 is the direction of the military within the capacity and roll it is used, with the M14 being left behind in the dust. The newer platforms are by design modular, having greater versatility, and their reliability have been greatly improved. But, nether of those 7.62 platforms can compete with the current wave of lighter modular rifles, when used in the capacity and roll as a combat service rifle.
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