I have always thought MTU stood for the USMC's Marksmanship Training Unit. I believe this is the contour of their M40A3 Sniper rifle, but I am happy to be corrected.
I have 0 (zero) experience with the 6.5X47, but I think your velocities are somewhat low, especially for a 26 inch barrel. I am not familar with IMR 8208 XBR, but perhaps a slower burning powder may produce better velocities without the pressure signs you are seeing.
