I think your issue with the 6.5 Creedmore is not performance, but actually size/weight of the bullet. I've got two and one last year I shot about a 300# whitetail/muley cross—it went straight up, flipped onto it's back and dropped dead. Great performance at 200 yards. But—I'd go for 300 win mag—larger case, more availability of off the shelf ammo/bullet weights. I've taken mine all over, from Canada to Spain and three times to South Africa. Nothing like knowing your rifle and how it shoots and being able to select bullet weights from 150 gr to 200 grains and NOT move the scope. Have taken everything from
steenbuck to red stag, ibex, axis to kudu at ranges to 450+ yards.