Hi, and welcome to the Forum, Kid!
Do you load for the .44 Mag already? If so, a lot of what I say may be old knowledge to you, so please excuse repetition!
The load already mentioned, 10.0 gr Unique pushing a 240 gr SWC cast bullet, may not be quite as popular and universally suggested as 2.8 gr Bullseye under a 148 gr WC in the .38 Spl, but that's quite possibly only because the .38 Spl's been in use twice as long as the .44 Mag and then some!
Looking thru my records, I've used "that load" with 9.5 and 10.0 gr in my 7.5" Redhawk and both work quite well, with the advantage rclark added that you can shoot it comfortably all day. With a 240 gr copper plated FP bullet, I've used 8.0 to 9.7 gr Unique and 6.5 gr of Universal. All three worked ok in initial can-killing tests. FWIW, plated bullets can be touchy--they worked best with the lightest loads when we tried 'em. And, you may find Unique to be pretty scarce on the market, so Universal is a good choice to use in its place (check the books.) In fact, many former Unique users have made the switch permanently!
I don't shoot a lot of flame throwers thru my RH, but 296 under a gas checked 240 gr SWC cast bullet puts on a good fireworks show from a 7.5" bbl when I do, so with the 5.5" it might be a bit much. Former advice with 296 from Winchester was to never reduce it, while former advice from Hodgdon with H-110 was to not reduce it more than 3%. At that time, since recipes weren't the same, I would have bet they were really close, but not the same powder. When Hodgdon took over distribution of 296 in addition to their own H-110, a couple of things changed: new recipes from Hodgdon are identical between the two, suggesting the guys who say they are identical TODAY are correct, and both powders can now be reduced up to 5% according to some data. I've used, and suggest using, a reduced load with 296 in places where the book oks it.
If you choose gramps' load of 2400, you're almost dead on to the load a buddy shot silhouettes with for several years, using an 8 3/8" 629. He likes the #429421 Keith bullet which comes out a tiny bit heavier (~250gr?) I think a 200 meter ram weighs about 75 lbs, and they'd go over easily with most hits. His advice on 2400 echoes gramps' comment, not only is each gun its own entity, but 2400 has a rather narrow window where it works best in many of them. In my buddy's case, it was a half grain wide, about a grain below book max. So a little testing may be in order with 2400. Don't give up on it just cuz the first loads aren't great--work up and down in tiny increments and you'll probably find a nice sweet spot in your gun.
Watch your primers, too: both 296 and H-110 need magnum primers (Winchester's WLP is a two-fer: it's ok'd for standard AND magnum loads) AND a firm to heavy crimp is required for best ignition. Unique, and Universal work nicely with standard primers and a light to moderate crimp. 2400 can use standard primers in a lot of loads, too, with a firm crimp suggested.
And, as always, be sure to check anything you read here against published sources! (Typos have happened.) Sixhot's advice to use several books as cross reference is very good practice, as well.
Rick C