Got a fancy framing hammer for my birthday - is it normal for it to feel this heavy?

Your buddy is on the right track. A framing hammer feels heavier for a couple reasons even when the number on the label says otherwise. It's ussually a 20 to 22 ounce head versus the 16 you're used to, and the handle is longer, so all that weight sits farther out from your hand. That swing weight is what your elbow is feeling, not just the ounces. Titanium lets makers throw more head weight on without the thing getting ridiculous, so a lot of these end up swinging heavier than a steel hammer of the same listed weight. You're not doing anything wrong, you're just holding a diferent animal.

That swing weight explanation matches what happened to me when I made the jump. First week with my framing hammer my forearm was toast, then my grip loosened up and I stopped trying to muscle it and it clicked. Give it a few jobs before deciding anything. And yeah, keep the lighter one for trim and small stuff. I keep my old 16 in the bag for hinge screws, stop blocks, anything fussy. Not wasteful at all, most framers I know have at least two hammers on the truck, some three.

Gotta push back on the 'you're not doing anything wrong' part though. An aching elbow is your body telling you something, and in my case it was the wrist snap. I used to fling my old 16oz hammer with my wrist, and when I got a framing hammer I kept doing the same thing. Big mistake. That head is way too heavy to be whipping around like that. Once I locked my wrist and swung from the shoulder, letting the head just fall, the ache cleared up inside a week. So he is doing something wrong, it's just an easy fix.