J-frame holsters will work if they have a retention strap. The Undercover is slightly smaller than a J-frame. J-frame holsters that use friction to retain the gun will also work as long as the friction device can be adjusted like many high-end leather holsters or kydex types.
I have never used speedloaders so I can't say for certain. But comparing my older Undercover with my S&W 642-2 the chamber to adjacent chamber distance is very close between the two guns. J-frame speedloaders might work.
I have always shot standard pressure 38s in mine for the most part, maybe 4000-5000 rounds, along with a few hundred +Ps. The Undercover is still as tight as when it was new. Oddly enough it locks up better than any of my Smiths or Rugers have over the years. Go figure...cheap gun, perfect lockup.
I am wondering if the MKS takeover has improved assembly line quality control on current Charter production. If so, I would consider a new 44 Sp Bulldog.
