Well my most immediate question is "can you get the dang moonclips for it!?". Does it come with any? Are they a fairly common pattern? Ruger's 9mm Security/Service sixes used moonclips, which are still available. In 38/357, those guns took the same speedloaders as S&W K-frames like that 19, so in theory the cylinder bore layout should be the same between the two families in 9mm.
You need to find an Internet vendor/maker of moonclips and ask them for advice. When S&W did a 9mm K-frame they didn't use moon clips, they used a very funky extractor instead. So this is VERY custom stuff you're dealing with. If you can't find a fast source for a lifetime supply of clips (20, minimum, in my opinion and I can make a case for 50!) you need to pass.
Assuming you can find the clips, it sounds like big fun! Most of those PPC barrels were optimized for 38spl 148 grain target wadcutters (twist rate, in particular) but usually shoot something like the Winchester 158+P lead hollowpoints (LSWC-HP) just fine.
But this is a 9mm version...hrm. Danged if I know how it'll shoot! Probably at least "OK" if that's a barrel meant for the 38 target lead fodder, maybe a lot better if it was really sized right for 9mm and has a twist rate set up for jacketed. That's the question here: did the gunsmith match the barrel type for the new caliber?
One thought: take a lead round-nose 38spl or 357 bullet (in the shell or out) and jam it gently into the muzzle enough to leave a mark in the lead. Now do the same with the same round in a "known 9mm gun", a good semi-auto with conventional rifling (not a Glock). Should be fairly easy to confirm if the dimensions in the barrel are roughly the same. Really slugging it would be best but...dunno if the shop would like that. You can also look down each barrel with a light behind 'em, and do a rough comparison of the twist rate by eye (holding 'em up at the same time).
Right, lets say you get it, and it turns out to be a tackdriver plus reloads faster'n greased poop due to the moonclips. Cool! It won't cost that much for a gunsmith to chop it to 4" and dovetail on a good Tritium front sight! Ashley's catalog has everything you need. You'd end up with a really bitchin' carry gun. 9mm revolver ballistics are often shockingly good, only a small step down from 357. They perform well in 2" barrels...in a 4" or esp. 6" they'll be wonderful.
Heck, you could even get the smith to slabside that big round barrel and cut the weight. Should add about $50 to the project's cost. The barrel chop, recrown and front sight all told, maybe $200. Would it be worth it? If the gun shoots well, has a slick trigger and reloads fast, hell yes! I'd put $500 - $550 into the whole project and end up with a cool old retired racehorse set up for the street in a heartbeat.
