Slugs

[Geezer]

If you don't believe it do the math, try it in a Chairgun or test it IRL. .22 pellets are around 0.03-0.035 in BC while .224 bullets are in 0.110-0.140 range. .25 is around 0.035-0.040 against 0.140-0.190 with .257 bullets. Reading this thread might also help And yes, I've been competing bullet shooters with my .25 pellet gun at 100M BR and it is a very tough job to keep up.

At the risk of pretending to be ballisticboy, I must point out that BC changes with velocity.

But your general point is right. Waisted pellets were designed for smooth barrels at low velocities. Then rifled barrels made them more accurate. Amazingly so (indoor 10M match, for example) at close ranges. But they and their associated barrels were historically made for 10-25 metres, without much regard for either retained energy or longer range accuracy.

If airguns had never existed, we would probably now, in ineventing them, at 12ft-lbs, go for a bullet-shaped projectile in 4-5mm or so diameter, optimised (with associated rifling twist) for accuracy to 50M.

[GPConway]

At the risk of pretending to be ballisticboy, I must point out that BC changes with velocity.

I'm not pretending to be Ballisticboy either but if the Ballistic Coefficient is calculated to be changing at different velocities then you're calculating against the wrong/inappropriate Drag Curve ... or perhaps you're using a 'constant Cd' approximation.
Maybe you're thinking about the Drag Coefficient - which does indeed vary substantially with velocity.

George