The only real value of boat-tails is when the bullet goes trans-sonic / subsonic. From that point on, the boat-tail exhibits less “drag”’ than a flat-based bullet

Whilst still supersonic, the “tail” of any jacketed (or lathe-turned) bullet has almost zero drag effect.

What is affected is gyroscopic stability and the effect of that on “precession” and thus, on group size. The more concentrically the jacket is drawn, the more concentrically the core is inserted and the more concentrically the jacket is formed over the core, the smaller the precession “wobbles” will be for a given barrel / load combination.

The additional step(s) used to form the boat-tail introduce minute alterations to the mechanical concentricity of the bullet. Thus, boat-tails have a well-founded reputation for greater precession at the muzzle and for “settling-down” further down-range than flat-based bullets. Somewhere on the intertubes are some words of wisdom on this topic from some bloke called Gale McMillan.

Shot from a “super-magnum”, the bullet may well still be supersonic at 1000 yards and thus not in the “wobbly” trans /sub-sonic region; boat-tailed or not.

Also, as a bullet exits the muzzle, the many tons per square inch gas pressure behind it exits with considerable violence. Everybody seems to be aware of the importance of precisely-cut muzzle crowns, but the effect of the escaping muzzle blast endures for several nano-seconds longer on a boat-tail than on a flat base.

All that notwithstanding: DAMN FINE SHOOTING!!

A number of guys have tried to build “better” sleeved guns using different oils as filler and playing with he tension of the barrel within the sleeve. Hasn’t worked.

There has also been a big battle over FB versus BT supporters for long range. That has been popcorn worthy at times.

Where we end up is at a point where conditions, the shooter, and the equipment all come toggery for one brief moment of perfection. And that moment becomes history.

This deserves an expanded story with much more detail.