[Atlas Sneezed]

Except the bullet weight tends not to drop much, so you end up with a longer bullet with a higher ballistic coefficient and better ballistics.

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You need a longer bullet to get the same sectional density. This requires faster rifling twist (new barrel), and reduces the powder capacity (lower max velocity at max chamber pressure) of the cartridge when you keep the same overall cartridge length.

If copper were as good or better, some shooters (competition, hunters) would already be using it. There is a reason why lead is used.

It’s the only metal over 10k kg/m^3 that isn’t radioactive, preciously expensive, or so hard it will destroy a rifle barrel.

[MileHi]

If copper were as good or better, some shooters (competition, hunters) would already be using it.

As the other poster noted, Barnes-X. Been around a while and, not some, quite a few shooters are using them.

I haven't and don't care to be forced to.