One of the original loads was a 270 grain bullet - the lightest.

If you are talking about a double rifle your bullet weight will need to correspond to the bullet weight for which the rifle was originally regulated. Otherwise, it's going to cross or spread.

In a single shot rifle you can get away with various bullet weights, but you want to find a load that shoots to the sights.

To answer your question: No I haven't tried a 250 grain bullet in any of my various .450BPE rifles.

I can say I am having good results generally from the RCBS 45-300 FN GC bullet. Although it is labeled 300 it casts about 325 to 330 grains. It's a really fine bullet from a current commercial mould that's readily available. Just a suggestion.
Here's a typical target from my single shot Henry:



Curl