RH, My M1A has shot more than 2500 rounds over the years including National Infantry Trophy Matches (rattle battles) that got it hot enough to smoke. I built it per AMU instructions in 1982 with a cr-moly Douglas heavy barrel and a Bishop super fat stock. It has not been re-bedded and still will shoot sub 1 moa with M852 NM ammo. (I have to put a scope on it to prove it now). If I was building one now, I would use a Krieger heavy stainless barrel and the heaviest walnut stock that the rules will allow. (I believe the super fat stock is not allowed in competition anymore). I would bed it per the AMU manual, except with Steelbed. The secret of bedding life is not to take it in and out of the stock except for major cleaning, and to store it un-clamped. that will preserve the preload and not compress the bedded area under the receiver. A good one will shoot x-ring when first clamped back in, and will be back to sub moa in 2-5 rounds.
I'm not familiar with the JAE stock, but if it will maintain preload and not crush, it's a winner. If you want to shoot it in competition, check and be sure it complies with the rules.
I've never shot an AR-10, but I am familiar with Garands, AR's, FAL's, H&K 91's and Cetme's. I'll take the M1A every time. If it has good parts in it, it can be made to shoot. Period. Military snipers still use accurized M-14's for good reason. Accuracy, and firepower if you need it.
Build you a good one, you won't regret it. Tom
Texas State Rifle Association Life Member
NRA Endowment Life Member
A big fast bullet will beat a little fast bullet every time