Thanks for the responses.
H&R never responded to the email I sent them, so I'm thinking I might have to give them a call. I don't work tomorrow, so if I remember, I can try asking them then. If they feel the Survivor will take heavier loads, that'll definitely open up some flexibility for me... but if I can get ahold of more 200 grain XTPs, I've decided I actually quite like what they do with 9 grains of Unique behind them. There's definitely some arc to their flight, but I found that load to be very consistent in my gun. I haven't tried punching paper with it, but several dead gophers can testify to the effectiveness of that load
Now, the 45 aside, if you have two bullets of similar construction and weight, is it true that you can generally apply the data from the heavier bullet to the lighter bullet in a bind? Or is that an incorrect and unsafe principle?
Also, thank you Lone Star for the opinion on 2400. I really didn't like how it performed behind some 300 grain bullets I had... although that was only one load so some tweaking might have helped. All the same... I have it, and I hate wasting money - so I'm planning to use up this container of it anyway... if I don't find a load in it I like, I might stick to Unique for the 45.