The best I can find is with a Rem hull, Rem primer, 14grs of Unique, 3/4oz, a Duster 2834 wad at 1200fps/9600psi. Duster wads seem to have a bit more pressure than Claybusters. But if you're going with 2 1/2" shells you may need to go with fiber wads which would lower pressure. I don't think there's an aftermarket for 2 1/2 28ga wads. Good luck but if were me I'd just order some 28ga fiber wads from www circlefly.com