I have a Sportsman 300 and absolutely love it. I run it on everything from a 6.5 Grendel pistol to a .300 WM. Very little POI shift and light weight. Yes it's aluminum, but it's still pretty tough. I have no experience with any of the Rugged cans except the .45 Obsidian. It's my favorite pistol...
I'm running a Griffin Arm. Sportsman 300 which is right at 8" on my 26" .300 WM. Maybe not ideal but very doable. To me the weight on the nose would be more of a concern that the extra length. Your mileage may vary.
I'm a huge fan of the Grendel in both the AR platform and a bolt gun. I agree that mag length max is a good place to start. I've had by far the best luck with ASC magazines. Both my rifle and pistol like bullets seated to mag max which for me is 2.28" Good luck.
+1 for the 6.5 Grendel. I've had great success with this cartridge on hogs and deer here in South Arkansas. I'd suggest an AR platform because you may see one pig, or you may see 20 at a time. Soft recoil and fast follow ups are a couple things I love about the Grendel. All the calibers you...