well there were several reasons...and i dont remember the exact numbers...but the 6x47 and the 6XC were a little under powered...and not that its a huge difference but i like having the extra horse power there if i decide to use it...ive also read that a lotta ppl have had accuracy issues with the 6x47 and i dont know how true that really is but it was enough to sway my decision just a little.
ultimately it boiled down to the price of brass...6CM brass is 68c the xc and 47 are about a $1+ or - a little...as far as the load im shooting goes yeah i could run it up another 100fps or so with the 115s and i could shoot the 105g class at around 3200 or so but why? 3120 would be 100fps faster than my speed now with the 115s and only gains me 1moa or 10" at 1000yds...the cost of that 10" is brass,barrel life,recoil and the biggest down side would be inconsistent accuracy.

at 3020fps my 850yd cold bore shot is about 90%...ive shot this load from 95-100degs down to 38-40degs and my drops dont change enough to even make an adjustment out to 1000yds and seating depth dont seem to matter either...from .020 to .038 off the lands it shoots the same.