296 should be a good choice for building fire breathing loads.
A word of caution, Follow your load data! 296 (& H110) have some specific requirements that can't be ignored. The problem with pushing limits is that you can exceed them easily with disastrous consequences. Working at or near maximum loads requires lots of attention to detail. Take your time and work up carefully. Watch for pressure signs.
A powder that's not quite as slow is Alliant 2400, I like it a lot in .357. I've not used it for .44 mag, but i suspect that it will perform quite nicely for your needs. It's more tolerant of lower power loads than 296 (H110.) I've not used them but I recall that Hodgden & IMR 4227 are another option for playing at the high end. Near is I can tell the VV N110 should perform in a similar manner to 2400. All of these will provide a very nice fireball