Your specific load doesn't show up on Hodgdon's online loading data, especially at the very low pressure you've reported for this type of load. The closest one (primers are different) listed is:
2 3/4"REMINGTON STS, NITRO 27,OR GUN CLUB PLASTIC SHELLS, Lead Shot, 12-ga, 1 1/8 oz., 23.5 gr PB, Win. 209, WAA12, 10,200 PSI, 1250 fps.
Your load is already 1 gr of powder over this load, which is already crowding the maximum pressure for 12-ga. If it were me, I'd not substiture anything else... in fact, I'd not use your load at all.
