I own one of the early model 16 270 WSMs with the 1 in 11 twist barrels. I have shot 150 BST’s, 140 AB’s, 130 BST’s, and the Barnes 129 LRX a long bullet.

all the stability calculators, including Berger’s, predict that all the bullets would be barely marginal stable, right on the threshold of instability. Even the 130 is predicted to be marginally stable.

all of these bullets shoot great from 100 to 500 yds. The longer bullets shoot the best. The LRX is king.
never seen anything that looks like a keyhole

So

Dont let someone tell you you need a rifle with a fast twist to shoot long bullets. If your rifle shoots well chances are it’ll shoot long bullets too. (Within limits)

Gonna test even longer bullets soon. Some bergers. Wanna find the limits for this 11 twist

all this 1 in 7 1 in 8 stuff is just getting irritating, especially for hunting rifles that shoot 90% of shots within 400 yards