I ran this wildcat cartridge through my internal balistics program. I took the 284 Win and necked it up to .375 and kept the standard shoulder. Here's what I came up with using a 14.5" barrel.

At 90% case capacity using IMR 3031 and a 260gr bullet, it should yield 1830 FPS at 40K cup.

At 100% case capacity using same powder and bullet, it should yield 2030 FPS at 49K cup.

Interesting. The MK-40 is a nice bolt gun, with a scope and break and in good shape this is a bargain for someone.

Wichita has a picture of the MK 40 on their website.