How are these better than other 1oz slugs?
Not being snarky, serious question.
And at $2.60 per shell, it's a very pertinent question. The short answer is that they're not better than 1oz slugs in most scenarios. In fact, they're worse in all but a select few circumstances.
Two reasons I prefer them while in bear country:
1) Harder lead projectile vs standard foster slugs. It deforms less and doesn't fragment, which means it'll penetrate deeper thru bear fur, fat, muscle and bone.
2) External ballistics are better. It's a faster and heavier hunk 'o lead.
Brenneke Black Magic:
602 grains (1 3/8oz)
Muzzle Velocity 1,502 feet/s
3,014 ft/lb of energy at the muzzle
Federal Premium 1oz slug:
438 grains
Muzzle Velocity 1,300 feet/s
1,642 ft/lb of energy at the muzzle
The compromises (and there's always a compromise)
It's a lot more expensive per shell
It kicks like a mule
It's a 3" shell, so mag tube capacity is reduced.
Heavier/faster/harder slug means over penetration is a serious concern in urban scenarios.