I picked up one of the Ruger American Ranch rifles, chambered in 300 Blackout. So far I have found it reasonably accurate, and the cartridge easy to load for.

It is a fairly light little carbine, but I haven't put it on a scale yet. Not sure if it would make your 6 pound weight limit.

Good luck in whatever you decide to do.

"The number one problem with America is, a whole lot of people need shot, and nobody is shooting them."
-Master Chief Hershel Davis