I have noticed the Lee data to be all over the board. Their "Ruger/Contender only" loads I haven't paid a lot of attention to even though I have a 454 I can shoot them out of. Lee also doesn't list brass, primer, or test gun so who knows what other factors there are in their data. I use it as a general guideline but don't trust it implicitly.
If you're loading for a strong gun, like a 454, Ruger, or Contender, the heavier loads may be safe but I'd check the Hodgdon data. The reason the Hornady manual doesn't list it is because the 250 gr XTP is for slow, light loads, like standard 45 colt. The 240 XTP Mag is thicker skinned for high velocity loads like 454 and hot-rodded 45 colt.
I've shot the 250 XTPs from my 454, in 454 brass, with a full load of AA #9 and had excellent accuracy. They'd probably disintigrate on impact with an animal however as they were going around 1700 FPS. A little faster than their designed speed of 750-1000 FPS at impact.
Hope that helps. Just out of curiosity, what gun will you be shooting these out of? You might want to put the brakes on H-110 entirely. It can be a tricky powder.