The Whitworth and MK X are FN action copies. I presently have an FN action Sako 375 and a MK X 375...had several Whitworths back when they were still marketed, and there is only a bit of difference, and it is in the quality of machining and finish work. The CZ 550 American I have in 416 Rigby and my former CZ 550 Safari are somewhat different from the Interarms guns and FN-Sako,

There is a difference in "feel", however. Blindfolded and wearing heavy gloves, I could pick out the FN-Sako with no problem. It is that much smoother and more "solid" feeling than the others. I never felt slighted owning any of these rifles, and would use any of them to hunt buffalo.