The other principal difference is that the M14 usually had a vertical Patridge front sight whereas the M15 usually had a Baughman Quick Draw serrated ramp. This is arguably a more consistent difference than the barrel configuration, as a number of oddball M15 barrel variations exist.
Yea, good point, I wasn't thinking about the sights. However, the sights IMO don't define these guns as much as the barrel type. The combat masterpieces, regardless of any "oddball" barrel, will have a taper barrel. IF you "special ordered" a taper barrel K38 8 3/8 in with a patridge front, its a model 15 due to the lightweight barrel. If you ordered a 4in K38 with ramp, with a heavy barrel, its a model 14. IMO the barrel is actually more definitive. If you look around, you will see target masterpiece (6 in) guns with ramp front sights. On the other hand, you will never see a model 14 with a taper barrel, and only a model 15 snub nose has a standard (heavy) barrel, any other original model 15 barrel should be tapered, even if its long. IMO, the model 15 snub, while not having a taper, is also not really a heavy barrel, because its a snub. The best way to explain this is that simply the sights were a byproduct of the barrel type, because ordinarily, when one wants a lightweight barrel, they also want it shorter than a target length of 6 (so 4in) and because they want it for carry, you get a ramp front sight. Because with the model 14, you want it a certain weight for competition, and because its designed to be a range piece, you get a heavy weight barrel. Because you plan to target shoot with the model 14, you get a patridge.
At least, that's how I see the differences. Its the same scenario for the model 25 vs the model 26.
It was Dayton Police Supply. These guns are very distinctive because they have the same basic type of barrel as a heavy-barrel M10-6, which has a rounded cross-section without the distinctive flat top rib of the normal M14 and M15 barrels.
You are correct about the rarity, however. This is one of those guns that's rarely encountered in the hands of a seller who doesn't know what he or she has.
Thanks for that. I could actually see many FFLs misidentifying such a gun, because you can't think its common knowledge to know there was such a limited run of 4in model 14s. There is one on gunbroker, no: 347864189