Norma uses/used a simular type you can look there too, I will see if I have any laying around when I'm back at the house tonight.
Belive I read somewhere they are also a good fire starter
My first was with a 410 slug, a doe, dont recall muley or whitetail. Out of my dads old Savage Model 24 22lr over 410, and i still have that gun I carry it for grouse once or twice a year.
For the 2 options I would choose the 6.5 and i would load it with the 143 Norma bondstrike when using for a backup and ELDX for working through the new caliber nuances and hunting local. And if you're looking for a challenge try the ABLR.