I have owned 4 Interarms Mark Xs in 7x57 and all of them were throated for 175 grain bullets and had 8.9"(?) ROT barrels. I have shot a variety of 140 to 175 grain bullets from them with good results. My only remaining Interarms Mark X in 7x57 is a rifle that I bought from member Weagle back in 2004 and subsequently trimmed the barrel back to fit a mannlicher stock. It is a consistent 2 MOA rifle, possibly due to the mannlicher stock's additional pressure points.
Just a heads up on a characteristic of some Interarms Mark Xs that I find annoying. If the rifle that you're looking at has the 'butterknife" style bolt handle, you need to be aware that the way the bolt handle is attached to the body of the bolt gives it a high lift, so you have to use higher mounts to allow that the ocular lens clear the bolt handle when you cycle the action.
Jeff
