WB
It seems Winchester was involved...
Saturday, July 26, 2025, 09:11

The .400 Colt simply used the 180 gr. .38-40 Win. JSP they were already producing. A true 10mm Magnum, almost identical to the .401 Heters. I trim my Herters to 1.27" while many .41 Remington brass typically run .131"+. Just a few thousandths and the only difference is my PowerMag needs the trimmed brass.

I think the Colt .400 was in the late 1960's or 70's. The Trooper MKIII would have been a more marketable platform, IMO. But Colt was having financial issues even then. Farming out some production and marketing Sauer and Astra re-badged guns.