Thanks for the responses. As to why I want one, I have 2 44 magnums and just want try a 500.
That is a very good reason to get one, or two or more. Same reason I did. Just be very meticulous before you actually make the exchange. These guns are notorious for being handled (mishandled) a bunch prior to finding first owner.
Do the standard revolver ops checks, and inspect for signs of bubbasmithing, forcing cone, gap, etc. I fell victim of this with my PC3.5". At home after further inspection I find it had 0.011" gap, hammer slop, buggered up tension screw head, then after removing panel I find all the screws and surfaces were corroded, the yoke screw was eaten up so bad it broke when backed out, furthermore it was 3+ years old (must've been stored in box for a good time. That was my 2nd ever new gun purchase, have learned my lesson. It is at S&W now, but surprisingly, with all of its issues it has, it shoots much better than, and produces equivalent velocities to the 4" which was just 4 wks old at purchase. Furthermore has a 0.0045 gap and even less end play. Also, I'm not certain if it is just my case but the cylinder chambers are more closely matched with the PC. It's as if the PC designs are engineered better, but the staff, perhaps at one point, needed to be caught up to speed.
Nevertheless, I would recommend the 3.5" over the 4" any day depending on your needs (beautiful fire rings that hit a target at over 15 yards). It might be much uglier, and even though the comp on the 4" looks sporty, it is really useless and tedious, and I often forget to swap it out (then I am left with a need of a new front sight).