Hi
which is the heaviest pointed bullet that can be stabilised by 1/12 inch rifling twist? i mean modern bullets like accubond or hornady interbond or barnes stx?
regards
yes

180gr

I built a 30 mag rifle with a 12 twist for shooting 180 grain Interbonds. I determined that the 12 twist is ideal for this weight range; plenty of room on both sides, although favoring the lighter.

To verify, I shot a bunch of 200 grain Sierra MK's out of my 12 twist 308 target rifle (which has digested many 190 grain MK's out to 1K yards). The 200's shot EXCELLANT.

My 1-12 30-06 loves the 150 Ballistic tips for accuracy, but I don't recall ever seeing a keyhole/stabilization issue with any bullet up to the 220gr RN (they didn't group from that rifle, but that's another issue)