It has been my experience in my 1967 336 Texan and an early 70s Glenfield 336, both with microgroove barrels, that Hornady 160s at 2400 fps are quite accurate. I have loaded a lot of these bullets over Leverevolution and have had excellent results.
The twist rate 1:10, unless you have a non-standard replacement barrel, so stabilizing those 160s is not a problem from that perspective.
There's either something wrong with the barrel, or the bullets. If there's nothing obviously wrong with the bullets (oddly different weights, visual deformity), it's the barrel. Have you checked velocity worth a chronograph?
Is the rifle new to you? Is this the first time trying the 160 FTX? Are you sure the barrel is lead free? Is the crown in perfect shape? Is the throat shot out? Can you see the rifling in the barrel? Can you see anything in the barrel that ought not be there?