Someone else was asking about buying one so I posted the pictures of one for sale in the THR thread listed below to save anyone some trouble looking them up.
It's a double barrel 12 gauge:
http://www.thehighroad.org/showthread.php?t=375709
The original for sale ad expires from view after a period of time even though it still exits in the data base through the URL link below:
http://www.huntingnet.com/forum/tm.aspx?m=2860929
Shooting a ML shotgun is pretty much like shooting any other modern shotgun or smoothbore muzzle loader. The extra steps required are to measure out the amount of shot and to insert the type of card or wad material of your choice under and over the payload.
Wadding can be as simple as newspaper, wax carton material, leather, thick fiber wads, thin wool wads, conventional modern plastic shotshell wads etc...
Patched round ball and/or buckshot can be fired out of one too.
I recently shot some pulled .22 long rifle bullets out of a smoothbore pistol to use like a short range scattergun.
Just about anything that can be rammed down a smooth bore can be fired out of it.
So they're very versatile and a lot of fun to shoot.