I think your 243 needs some work. Seriously. You should expect to see 1.5" groups out of a 243 with three different brands of ammo. Good news, is I usually see the same things with factory guns and fixing could be very easy. A nice bedding job, with a free floated barrel should do the trick. Your gunsmith might check the crown for straightness. Maybe, a quick no go headspace test.

As far as the 270, from previous expience, don't mess with it. Its a nice shooter, not a benchrest gun, and seems to be doing more than its spec'd to do.

What range do you shoot at? I used to shoot near pineville, WV when I lived in Mingo County.