I have been playing with this idea for about 7 years and finally got a "round tuit" and took the plunge. I made a switch barrel for my circa 1915 model 1899 takedown chambered in 264 LBC, better known as 6.5 grendel. It was at the limits of my talents, but I am proud to say that it came out great. I had to learn to turn square threads, grind my own single point cutter, buy a t-slot cutter for the extractor notch and top notch for the bolt. Then the barrel contour had to be turned to match the takedown forestock. It was quite the learnig experience with lots of pucker factor and gnashing of teeth.
I have just stared cast bullet work and she shows promise even with the 1 in 8" twist. 14 gr of sr4759 under a noe 125 gr bullet gave 1.670" 3 shot group and 1965 fps. I was surprised at the high velocity and will be going out soon with 12 - 13.5 gr. Off to a good start.