I was looking at some lightweight hunting rifles yesterday and have seen the Christensen Arms rifles at my local Sportsman's Warehouse a couple times. I was checking out their website and noticed that the 450 Bushmaster was listed as an option for the Ridgeline series and a couple of the others. I have never used one of their rifles, but it looked interesting. This model is a carbon wrapped barrel. I definitely like seeing more manufacturers offering a 450!
https://christensenarms.com/ridgeline/