What shot size?
Keith - depending on what shot size, there are plenty of cheap ammo sources. My range only allows #9 shot (for now), but Can Tire, and Wally Mart usually have the 71/2 and 81/2 shots in 12 Ga. Skeet for about $20 for 100 rounds.
The ones I have tried are Federal and Winchester, and they cycle my semi ok, and no prob. with the pumps.
best
Dr. O