I'd not buy a 44mag unless it's a new one as MSP recommended, one with a barrel made by Marlin in 2007, a frame serial number prefix of NX or HX and matching last 3 digits on the left side of the barrel underlug, if it's older, don't buy it. Unfortunately, I'm not sure when Marlin started making the barrels last year, or if it was earlier, so there's no positive way to know unless you get an accessory barrel fitted to the 500 or 30-30 frame after you buy it, any accessory barrel will be current production and those are the good ones, older 44mag barrel had oversize bores and were almost impossible to get to shoot good without going to oversize cast bullets.
Concerning the 500 Handi, I'd ask to remove the forend and make sure it locks up tight with no wiggle, they're known for shooting loose, H&R will replace any barrel that does, but you should know what you're getting into up front. Speaking of that, their recoil with factory ammo is not user friendly and they get sold a lot in our classifieds due to that and the expensive ammo. If you handload, you can load it any way you want from 350-440gr cast bullet loads with Unque or Trail Boss, to hot loads with 700gr cast bullets and Lil'gun at 1400+fps. But if it's a big bore you want, the 45-70 is the one to have, but that's a topic for another discussion.
Tim
http://www.gboreloaded.com/forums/index.php/topic,26264.msg503417.html#msg503417
