vaslugger
Hey mike!
The Hornady .452/300 grain XTP Mag is a very good bullet as is the 44/300 but I am not sure it is billed as a XTP MAG. There have been some problems reported with the XTP Mag when they are shot a shorter ranges at deer. The copper on the bullet wraps over into the nose of the bullet and in some case at close range they do not always expand. The regular XTP is really, I think the better bullet to 130-140 yards.
I would also suggest that if you are going to buy them, instead of buying the packages of bullets and sabots, buy a box of the bullets in bulk, then get the sabots that will match your bore.
As a suggestion I would suggest you also look at the .452/300 grain Speer Gold Dot. It is a bonded bullet and will not come apart. It is effective from short ranges to 200 - the BC on the bullet is a pretty nice .233 as which is several points higher than the Hornady.