Years ago, I had a friend that had a 240 Weatherby reamer ground by JGS with zero freebore, non turn neck and ran in a #5 contour, Shilen Match SS barrel,26". I was with him at his first range outing, I re-loaded, he shot.
The rifle was shooting bug holes within 12 shots, 85g Sierra BTHP very, very fast, tiny groups. Then we tried the 80g Sierra Single shot pistol bullets, same thing, very fast, tiny group, 3800 fps. Next, 75g Sierra HP...almost 4000 fps at the accuracy node, buy now, those 12 cases were trying to give the primer pockets.
A few years later, I built a 6 Rem AI with zero freebore, no turn neck, duplicated the velocity and accuracy, and have had several since then.
80g Sierra single shot pistol bullets or the 80g Blitz BT shot at 3800 fps are not Rock Chucks shots you want to post on You Tube, they will ban you!
If I were to buy a new Vanguard in 240, I would make sure there is enough shank on the barrel to set it back when it is brand new with a zero freebore reamer, then rake havoc on varmints, deer, and hogs.
6AI
240 Weatherby
both with zero freebore
12T
26"
70g at 4000-12T-26"
" 4100-one 14T I had-26"
80g at 3800 with R#19
" " Superperformance
Ever seen chucks fly out of the scope so fast that if you blinked at the gun shot, they just disappeared?
How about watching a chuck fly straight up, then come down in two pieces with a gut string attached?
Half grown chucks look like they have been shot out of a cannon!
Also, how about two chucks side by side, put some English on one, knock the other off the rock with him knocked coo coo!
6 AI with Win 760 has pretty good barrel life, not so much with N550.
I don't know about the 240 Weatherby with all that freebore, but a custom chamber with zero freebore is a wicked mamma jamma that will give you some memories that will last a life time....make some memories.