Brent, I do believe its Metford, the barrel is marked Metford on top, I wouldn't know the twist or how to measure it, the rifling barely shows on a chamber that goes 3 inches into the barrel, they are defiantly there but not very pronounced. The original bullets for the were if I remember right were 360 grn hollow point, 540 grn for express load? and 570 for match, this is all I have found so far, so I thought I would start there.