Thor's Hammer!!
Haven't got a Handi 44 Mag, but do have a M94 Win 44 mag - they work great in Winny. Don't know if I believe the chrono but I got 1500 fps out of it with much lighter loads of 2400 powder than most books have for max load with a 300gr jacketed. If the chrono was right, it was about 200-250fps faster than what it should have been with jacketed.
That bullet worked pretty good in my Handi 444, but the accuracy wasn't as good as a custon 290gr WFN mold I got. The crimp groove was too far back from the nose with the 310gr in my 444. Of course, I still loaded them, but crimped on the outside. Just didn't have the accuracy in it.
But, I couldn't hardly get the M94 away from my buddy. He calls my 444 "the Thumper", & the M94 "Thumper Jr". The sun was behind us & we could see the slugs flying through the air - looked wicked when you'd see them bolt through the air & slam into a rock. Tough choice on which to carry in the woods this year.