Not MEANINGLESS but they MAY not mean as much as we think.
1. With MOST manufacturers(or really just who markets the projectile)the BC is inflated. Therefore, two different bullet BCs, may not vary as much as we are lead to believe. Bullets with higher prices almost always have a higher advertised BC. This is the case of the 300gr .452 XTP vs. the 300gr SST. Not as much difference as they would like us to believe.
2. BCs may be calculated at slower velocities. Slower velocities yield higher BCs, ATBE.
While it is true that BC's can mean what you want-- they are not automatically inflated THAT much. When you buy a loose Hornady 300 gr. XTP or a 300 gr. Barnes Original, just how is the dumb old bullet to know that it might be shot out of a Savage at 2100 - 2300 fps? Only Sierra gives you the numbers to begin to correct for a bullets actual use-- but they don't directly participate in the muzzleloading market.
A Winchester 260 Platinum Tip 260 grain has a stated BC of .200. That BC is exact-- as exact as can be under the conditions tested. However, when Olin developed that bullet, they shot it with 90 grains of Pyrodex RS in several muzzleloaders, what they felt was a common load at that time.
It was shot on-site on their own Doppler radar range, and the published static BC of .200 is a 200 yard average. No deception or inflation at all-- that is what it did, with radar printouts to prove it. It won't do that with three pellets, but they do not claim that it does or ever has. Can we fault Olin?
The Barnes MZ-Expander has been on the market some ten years; I don't know exactly when it was introduced. 100 grains of loose blackpowder FFg or Pyrodex RS was the max. load in many guns, why would it be tested with more? Triple 7 was introduced at the 2002 Shot Show, and the 2002 seasons was when it was first used. To this day, Thompson and several other manufacturers only allow 100 gr. T7 FFg as a max load. Yet, many people are going quite a bit hotter than that.
Can a muzzleloading bullet manufacturer be expected to develop a static BC with a load not allowed by the majority of muzzleloading manufacturers? It makes no sense to do so, when the higher the velocity, the lower the BC, and the load is not generally allowed.
A Buffalo 375 SSB has a stated BC of .296. Ron Dahlitz paid to have that BC independently developed from 150 gr. Pyrodex select fired from a Remington 700ML-- 100 yard chrono-to chrono. Can we ask for more?
There are a few that are intentionally designed to mislead. PR Bullets prints a .371 BC for a .44 / 300 gr. Dead Center fired with 110 gr. T 7. It is impossible, ridiculous, and smarmy.
Nevertheless, for those who really want to know what flies from the best of two bullets in their gun does not have
that daunting of a task ahead of them. Sight in at 3" high at 100, then see where they group at 200. Knowing where your bullet is hitting at range is a big part of what it is all about, anyway.
A standard Remington .45-70 cartridge load with a 300 grain bullet is 1810 fps muzzle velocity. There is no reason to believe that a ".45-70" bullet, as in the .458 Barnes Originals, have BC's developed with anything much faster than that 1810 fps-- I can tell you they positively were not recorded from 2350 fps loads out of a 10ML-II. Adding over 500 fps to that bullet will lower its static BC number, but that is hardly condemnation of its stated STATIC BC-- it says "45-70" on every box of loose bullets.
