OK, here we go, take a deep breath and release, feel the thoughts of the 44 fading from your mind, along with the possible throat issues, accuracy questions, etc,etc.
Now. I bought a 500 for my son-in-law (now EX) that lived in Indiana, but he departed before the gun arrived. I was going to sell it, but there was no immediate takers, so I sent to midway for a $19 sizing tool, and the Lee 440gr FNGC mold, also $19, and a $28 set of Lee dies, I bought 100 rounds of brass for $55. So I have about 125$ in reloading stuff. The mold is very easy to use, my wheelweight+ metal comes out at 430 gr from the mold, needs very little sizing actually. I can tumble lube them for my "light load" or with a sizer die and stick lube. I do not use gas checks, they are not needed, and are expensive. I use 2 loads, one is 14.5gr of unique and a magnum large pistol primer, the other 21 gr of Blue Dot and a std lg rifle primer. The light load wil shoot 1.5 " groups @ 75 yards, the heavy load about 1.8 ". That is what I am using for deer this season. If your son can shoot the lightest field load for a 20ga, he will have no trouble with these. I deliberately reloaded the same case in testing and after about 20 rounds the only difference is some black around the casemouth. My reloading cost estimate for the round is approx 12 CENTS, not counting the dies/ mold investment. I expect them to eventually be so cheap to count, the first 500 have not even got them broken in yet.
The 500 is the easiest gun to cast for and load I have ever used. The brass is very durable, it is like shooting 38 wadcutters supersized, not loud, does not kick much. and will shoot through a 3/4 plywood and a foot of phone books @ 35 yards. It also makes people at the range raise their eyebrows so far their hats fall off. There is no way I would trade my 500 for a 44mag. If you want both, fine, but swapping the 500 away would be a big mistake. Give it a thorough try first, I guarantee you can sell it here in a couple of days if you dont like it. But you wont. You put a box of reloads down the range and you will never let it out of your sight.