In the late 1960`s Colt produced an experimental handgun round they called the .400 Colt Magnum. It was perfected by a Colt engineer named Bob Roy who was most likely inspired by the .41 Colt
Special of the early 1930`s but was never adopted. Mr. Roy started working on a larger more powerful round for the medium frame Colt revolvers such as the Official Police/Python size revolvers and began development using a modified 30-30 case. Once the load was perfected a small lot of "W-W 400" headstamped cases were procured from Winchester and loaded at Colt as the gun neared production status. Just before Colt management was to give the green light to announcing and producing guns in the new caliber Smith & Wesson announced their S&W .41 Magnum round and revolver, and that killed it for Colt. One can only imagine what would have happened if Colt introduced their .400 before S&W did their .41 ( Colt Single Action/New Frontier- Python- Trooper). Since I have only one round I could not pull the bullet to get some true measurements of the bullet and powder charge but I did measure about 1/8" below the case mouth of the 400 Colt and a 210gr JSP .41 mag cartridge. The Colt was .420" wide while the S&W was .430" wide while the 400 weighed 293grs. and the 41 weighed 335grs.. The top photo shows the "W-W 400" headstamp while the middle photo shows the .400 Colt alongside a .41 Mag. The bottom photo shows the .400 Colt on the left of a .41 Mag cartridge..