Call T-Bird ammo and ask them about the 5070 and what they reccomend. I've never used it but 250 grs. sounds like an extremely hot round and I would be worried about using/shooting it.
Most guys run about about 215-220 grs. of powder when reloading and get very good results. Some guys do run loads that are hotter then this but they have worked up to that load. Hot rounds will shorten the life of the brass, they will beat you up shooting them and more then likely will burn the throat out of your barrel faster also.
Some of the companies currently making powder will have load info on the jugs, these are suggested loads and it's always advisable to do your own load work. Just remember to look for pressure signs when doing load work, flattened primers, hard extraction, case head failure are some of the things to look for.