Those barrels are made by MGM using a Brux barrel. They are excellent barrels. If you want a cheaper barrel that is very similar go to Haus of Arms. They have one for $480 but its not rated for smokeless. They are light years better than a factory T/C barrel. Bullberry offers one in 50cal. MGM does not. Its also about $660 though. They use Douglas blanks which i love although Brux is a better barrel. https://www.bullberry.com/black-powder-barrels

The really nice thing about the ASG barrel is you can change to LRMP later if you want and of course it is rated for smokeless. However the one that is $680 is also a full bull. In other words i think its 1" the whole length. The one for $880 is 1" for 9" and finishes at .8" Bullets will need to be sized to about .450 to shoot in any of the Brux 45s. So you will need a sizing die. Shooting soft lead conicals you can get by with a cheap Lee .451 or .452 sizing die. So add another $160 for an adjustable die if you want to shoot jacketed bullets sabotless.