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.400 Colt Magnum “Experimental”, FMJ, One Cartridge not a Box!


Please see below for more information.

Please click on the picture for more detail.


One Cartridge , not a box! Box in the picture is for reference only, from the 1960s Colt factory empty primed brass cases from which the cartridges were loaded.

One “Live” Cartridge, not a Box: 400 Colt Magnum experimental cartridge loaded the a FMJ (Full Metal Jacketed) bullet. Loaded in 2022 by a licensed F.F.L. ammunition manufacturer exclusively for “A Call to Arms, LLC” using “then new, Colt Factory Brass, Primed Cases with a “W-W 400” Head-Stamp produced  by Winchester in 1960s. Loaded with  a 200 grain FMJ (Full Metal Jacket ) projectile and 7 grains of  IMR Trail Boss Gun Powder.

For the “Jacketed Hollow Point” version please see below in related items.

History of the 400 Colt Magnum Experimental cartridge:

The (experimental / prototype) .400 Colt Magnum experimental cartridge of the mid-1960’s is known as the cartridge that was never was, or that is : not offered for sale to the general public.It was designed by Bob Roy, a Colt Engineer, and it was inspired by the .41 Colt Special idea, that Colt experimented with, but also never adopted in the early 1930’s.Bob Roy restored the concept of a larger, more powerful cartridge for the Colt, medium frame, “Official Police” revolver and worked on developing this cartridge, first with modified .30-30 cases.Once the load was perfected, a small lot of “W-W 400” head-stamped cases were procured by Colt from Winchester and loaded at the Colt factory for testing as the revolver neared production status.Unfortunately, as Colt management was about to announce production of the revolvers in the new 400 Colt Magnum caliber, Smith & Wesson announced their new .41 S&W Magnum cartridge and revolver, and Colt decided to discontinue the project.  Thus, this cartridge was never offered to the general public by Colt or Winchester.  These “LIVE” cartridges for sale here were custom loaded in 2022 by a licensed FFL ammunition manufacturer exclusively for “A Call to Arms, LLC” using 1960s (then new) unfired, primed cases, which were purchased from a collector by “A Call to Arms, LLC”. No loaded cartridges were available to the general public, although a few collectors/dealers “allegedly” received a few cartridges from a (then) Colt employee; however, to my knowledge, no proof of that fact is available, so please judge for yourself.

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