Any smoothbore can be used with shot. The biggest issue is the limitations imposed by the unchoked barrel.
That Harper's Ferry is a .69 caliber and will use 14 gauge wads which you can order from Track of the Wolf.
One ounce of shot and about 60 grains of FFg would be a good starting load.
I use a couple of 1/8 inch thick over-powder cards between the powder and shot and then a thin overshot card over the shot with good results in my fowling pieces.
You can convert caliber into gauge by dividing the caliber into 1.67 inches and then cubing the answer.
Since it's actually a 14.17 gauge, 14 gauge wads will be a little on tight side of fitting the bore, which is a good thing.
Last edited by B.L.E.; February 3, 2013 at 08:42 AM.