I always tried to "build in a discount" for ammo sales... that is, you have a 20rd price / a 100rd price / and then a price for a full tin/case whatever.
So on your Bulgarian 54R you have signs posted:
$5/20rds call this a "sampler" (25cents/rd)
$21/100rds call this a "shooter" (21cents/rd)
$45/300rd tin call this a "blaster special" (15cents/rd)
You get the idea.....brings in the buyers who balk at your 20rd price. If I see a guy with a crap load of ammo and only a price per box...I think he wants that price for all of it!
Sure guys will want a "deal" on two tins so don't put the one tin price too low!