When you wipe between shots, make sure your hammer is on half cock or you will plug the nipple hole with crud. You should be able to hear air being forced through the nipple as you push your ramrod down ensuring your nipple is clear.
Looks like they are starting to get hard to find too.
TOW has this to say: We are temporarily limiting purchase of this item to one twelve pack per order. We will manually edit your order if your order exceeds that amount.
If you are shooting a patched round ball you don't need to concern yourself with lead fowling. For a round ball .008-.012 deep grooves are good. If they are too deep, your patch might not seal well and let the gas escape past the ball and ruin your accuracy.