Brent,
Wiht spitzer bullets in smokeless centerfires, bullet stability actually increases with distance.
Bullet instability occurs for two reasons:
1) Air pressure on the front end of the bullet overcomes the center of mass toward the rear of the bullet.
2) The bullet enters the transonic zone between about 1100-1300 fps, which introduces weird forces.
With spitzer bullets fired from smokeless cartridges, bullet stability actually increases until velocity drops enough for the bullet to enter the transonic zone. This is because air pressure on the sharp front end decreases rapidly (with velocity) but spin slows down at a much slower rate.
A .30 caliber 150-grain Ballistic Tip is not only not nearly long enough to be marginally stabilized in a 1-10 twist, but when started at 2800 fps it won't be anywhere near the transonic zone until close to 1000 yards. And even if the barrel is a replacement, I sincerely doubt it would have a 1-14 twist, since they're almost unknown in .30 caliber centerfires--and 1-14 would still be plenty to stabilize the 150 BT.
I copied the photo of the target and blew it up and three of the four bullet holes at 200 yards are perfectly round. The other hole shows a slight opening on the right side that looks like an irregular tear in the cardboard, rather than an oblong shape to the hole.
Yeah, there are reasons other than twist for bullets to be unstable as they leave the muzzle, but if a 150-grain Ballistic Tip from a .300 Savage is stable at 100 yards it will be stable at 200. The same applies to a worn crown. Crooked-seated bullets aren't unstable, they just leave the muzzle with their base at a slightly different angle than straight-seated bullets.
Which is why my money is on a forend bedding problem.
