I've carried my 13 (4" barrel K frame) in a vertical shoulder holster with the "spring type" retention", usually in cooler weather where I can employ a zip up hoodie or leather jacket, zipped about 1/3rd up, from time to time. It IS more suitable for use if your driving/seated, and is one of the few ways to carry a K frame actually concealed. Otherwise, if you can't practically open/hip carry, I would use an iwb holster with a compact or sub-compact. Fortunately, a lot of my Glock 30s holsters are quite handy at carrying a 639, too, so I keep those as a viable option. Older shoulder holsters that were designed for the S&W 15 would work, too, as a 4" K frame holster, but again, the need for a jacket is a factor.
I have what is also called a "tanker holster" for my 1911, which is the type I believe the OP was asking about,, but, due to a strap coming around the front and the holster being more towards 10:30 on your torso, these also would require a partially zipped jacket to conceal.....These were designed more to keep a sidearm from catching on hatches, etc. for tank and air crewmen, and in the case of the 1911, SOP was to carry it hammer down on an empty chamber in these holsters, rather than "hammer back, safety on, bullet in chamber". The idea was that it was for TRANSPORTING a sidearm, rather than concealing...If a pilot or tanker got in a situation where they actually had to USE their sidearm, (instead of the machine gun, for a tanker at least) they would already be out of vehicle, with their pistol drawn and a round chambered, not in a "quick draw" situation....
