Just watched Monster Bucks XI and one of the guys was using his new wildcat caliber .400 Marlin in a Marlin lever gun. From what little was shown of the cartridge, I could guess it looks like maybe a .450 Marlin necked down to .40 caliber. Anybody heard of this, or have any info???

American Rifleman had an article on in back in 2002 (may have been the March issue). Essentially, it's a .450 Marlin necked to .40 caliber. Sort of a neat idea, and in terms of performance, it would be close to a .416 Barnes.

Lee Martin
www.singleactions.com

I saw that too and I wanted to know about it aswell. It looks like a neat caliber that i wouldnt mind learning more about.

It sounds identical to the .411 JDJ as chambered by SSK. His is based on the .444 Marlin case, as well. I wonder what the bullet diameter of the guy's rifle in the video was.

If I recall correctly from the article in American Rifleman, the bullet diameter was .408. The bullets used were for blackpowder muzzleloaders using a sabot...

The 400 marlin uses standard 40 cal. bullets. The 41 Marlin and 41/45-70 uses 410/411 bullets.

Yep, I remember the article also, the Author had necked down the .450 marlin to take .40 caliber muzzleloading bullets (not sure what the diameter was), because it was a new type that was tough enough for what he was using them for. He had a special measuring device taped to his lever gun reciever to keep track of the pressures created since it was his own design. Looked like a great idea. I would assume it is the same person in your movie.