The Ballistics Coefficient of a projectile is a function of the Sectional Density and the Form Factor (drag).... BC = SD / FF to be exact.... If you look at a typical bullet, say the G1 Drag Model, for example, by definition it has an SD of 1.000 and a FF of 1.000, so the BC is 1.000.... The FF for a sphere (roundball) for example, is 1.55, so if you had a sphere with an SD of 1.000, it would only have a BC of 1.000 / 1.55 = 0.645.... Pellets, like a sphere, have more drag, and hence a higher FF (which is a measure of the drag) compared to a bullet.... In fact, they are pretty close to the drag of that sphere, for a round-nose pellet like a JSB Exact, even worse for a wadcutter, they might have a FF of 2.0 or even more....

In your question, you specified that the bore and weight are the same, so they have the same SD.... The SD is the weight (in lbs.) divided by the caliber^2.... For a 25.4 gr JSB King, .25 cal the SD is (25.4 / 7000) / 0.25^2 = 0.058.... If the FF is 1.5, the BC would be 0.058 / 1.5 = 0.039, which is pretty close, so that was a good guess for the FF.... If you had a bullet the same weight, but less drag and a FF of 1.0.... the BC would be 0.058 / 1 = 0.058.... That higher BC is an indication that it will lose velocity less quickly as it goes downrange, and that it will also be less affected by the wind.... so the bullet will have a flatter trajectory, higher retained FPE, and less wind drift than the pellet.... all because its shape has less drag....

Bob