The 640 Pro will load with Loose Rounds, Speed Strips, Speed Loaders, as well as Moon Clips.
The .025 Thick TK Moon clips do not seem to be terribly fragile.
TK is carrying a new Product, a California Competition Works Moon Clip Carrier made for J Frame 5 shot Moon Clips. They are a little pricey at $20 a pop, but will last a lifetime. I picked up 2 with my 10 PK of Moon Clips.
Welcome to TK Custom.com & Moonclips.com
A note on Ammunition and the Moon Clip 38 Special. All 38 Special Brass is not made exactly the same. Winchester will not work in .025 Moon Clips. The under cut is too narrow fo fit in a .025 thick moon clip.
Speer, Hornady, and Mag Tech will all work fine. Not sure about other brands of ammo.
The ability to reload with moon clips really makes the J Frame a much better carry option. Especially when the moon clip reloads are in the Moon Clip Carriers mentioned above for lightning fast access to your spare ammunition.
The 640 Pro comes with very good sights for a Carry Revolver also. I do not see any bad points for a Belt Carried small Revolver, other than the price being a little salty. For pocket carry it is a little too heavy in my opinion.
Bob