Not a muzzleloader comment, but I do use the XTP in a custom made slug gun. It is a break open .410 shotgun that has had the barrel double wrapped and then rifled with and extremely fast twist rate. We use re-primmed AA .410 shotgun shells, 50.5 grains of IMR 3031 and top it with a .410 XTP bullet. Absolutley devastating on whitetails and I have never seen a failure. Shots from 10 yards out to 170 yards. It is legal in lower michigan (shotgun only) to use due to the plastic hulls classify it as a slug gun. I do not know the velocity of this gun, but I have never seen the bullet fail.
In the 30 yards the deer went, what was the bloodtrail? Any exit? How was the internal damage? Did you find the bullet?