I've heard of an AR10 or two that has come from Armalite with a buggered up bore, one of the owners of these barrels who suspected as much had slugged his barrel to see what the bullet looks like after exiting the barrel. What he saw suggested that the bore was out of concentricity and that the bore was not parrallel from bore to muzzle, this was pretty long ago though so if they are having problems it's not a new thing not that that should ease your mind.
My AR10 performs pretty well so I guess I lucked out. To be fair though I do think I've got a pretty short throat on my AR10, I don't mind it so much for handloading because I'm able to obtain good accuracy with all my bullets seated to magazine length but with factory ammo some of it has it's bullet seated out further than what the gun likes for the sake of accuracy. Most all of my loads fired through it are handloads though so it hardly bothers me.
An AR10 is still a good deal though in my mind even if you buy an AR10 A4 or an Eagle Arms AR10 and yank the barrel to have somebody like George Gardner put a new one on there for you if the original barrel is a turd. Knights Manufacturing SR25s aren't as great a deal in my opinion and people have had issues with Knight's customer service, even an AR10 A4 that has to have it's barrel replaced with a better tube is likely to end up being a better deal than an SR25 by the time it's all said and done. But that really is just my opinion.
