I want to preface this by stating I am not an expert rifleman or gunsmith or such, only that in my experience my own Remington 7400 has been an outstandingly good little autoloader in that it is reliable AND accurate.
I've written about it many times, mostly to tell that story about it.
If you like or want one of these 7400's, I'd say go for it.
Mine has over 300 rounds through it without ever jamming. I've shot 180's and 220's through it and both were accurate, with the 220's printing a couple/three inches higher.
I've been told the gun would last a bit longer if I switched to 150's. Maybe, maybe not. I'll continue to use the 180's I've got, and may try the 150's just for fun.
The gun has seen two configurations so far, with the third still in progress because I have not doted on the gun much lately.
I was playing around with parts and came up with what you see there. FUN GUN.
It's going back to being the hunting rifle it's intended to be, though.
I'm digging up a picture of the target my buddy shot at 100-yds. with the 220's. THAT is pretty accurate for a .30-06 carbine autoloader with the 18.5" bbl.
All that said, the BAR is a different rifle and in a catagory unto itself.
I've got one of those, too, in 7mm Rem.Mag.
Yes, it IS accurate; more so than the 7400, but, it's got the B.O.S.S. feature. Big plus for tuning the accuracy.
I don't know what your grampa wants the gun for, but either one would suffice for hunting.
I think the BAR is preferable for having a 'nice' gun. It's just SMOOTH!
A BAR Stalker in .308 or .30-06 would be excellent. The '06 is available with the BOSS.
If you can live with the 4+1 capacity, it'd be a superb choice.