If I read the law correctly no calibers (factory loaded) became legal that would significantly out perform a 12ga or 20ga sabot slug rifle save for 45/70 and certainly not a smokeless capable ML.
I personally do not see the law having much if any affect on anything other than rifle and ammo sales.
Not like they legalized cartridges like the 308 Win or 30/06.
The 450 Bushmaster factory ammo has MAYBE 50 yards more effective range than sabot slug ammo.
350 Legend again if the paper ballistics of factory ammo are correct has no more of a effective range than a shotgun sabot ammo.
Only caliber that is now legal, again if I read the law correctly, that has the potential to out perform shotgun sabot ammo would be the straight walled 45/70 and using factory loaded ammo for all practical purposes in the hands of the average shooter using a plane Jane non tactical scope its at best a 250 yard deer cartridge. Can it reach out to 300 yards? yes, but only if the shooter has the practiced capacity and optics and can compensate with for the more than 24"of drop the 45/70 factory ammo with a 325 grain bullet (common 45/70 factory ammo loading) at 300 yards
As a reloaded I would if given a choice between a slug rifle and a rifle in 450BM, by a rifle in 450 Bushmaster as factory shotgun sabot ammo is over $5 a round now.
I must tell you on at least a half dozen occasions seen guys at my rifle club shooting Savage 220 20ga slug rifles' and I was mightily impressed with the 100 and 200 yard accuracies of that gun.
If I were to forced to buy a slug gun right now I wouldn't even consider anything else but a Savage 220.