I seen a pull off barrel that was chambered for the .50 BMG necked down to 6mm once. The guy said he was burning a ton of powder and was only able to get alittle over 4,500 fps. with it.
I`m in Alaska now, but when I get back home in Aug., maybe I`ll try necking some of my primed .22 rimfire cases down to .17 cal. Make my own .17 Mac11 ammo.
