Do you mean the Mossberg muzzle loader barrel for a 12gauge shotgun?
Probably knock you over quite quickly. If kept on target, i'd do a little something... By little something I mean total destruction.
On a side note, I have found my new gun...
http://www.youtube.com/watch?v=CvncpT4EVzQ
On another side note, my daily driver dream...
http://ropkeyarmormuseum.com/video/M4A3E8_FieldRun_Large.wmv
The Easy Eight baby! Nothing like 1100 cubes of pure ford muscle, backed with a 76mm main gun, 2 .30 1919's and Ma Deuce on the turret.
Man I wish I had the money. Someday i'll be collecting those kinds of guns...