Mike's DT 10mm run much shorter than 1.260. They are consistently between 1.243 to 1.253.
Tried more crimp earlier and had more problems, but not as much as you're suggesting - may be worth a try. My Glocks/Wilson are running fine with 1.245 OAL and a .422 taper crimp. I'll keep experimenting.... Beginning to think its the Wessons.... in 10mm....
Navy Corpsman, 1971-1975; NRA Patron Life Member; The 10mm "...more energy at 100 yards than a .45 ACP at the muzzle." - Massad Ayoob quoting Col. Jeff Cooper