on second thoughts it could just be the front rammer oring, you need an oring kit either way mate so get that ordered and post up when you have it.
Turning the lpr pressure off will diagnose it down to two of four possible orings, turn the low pressure reg (the little one sticking out of the front) down untill the little gauge on the side reads naught, if the leak stops then you know its either the front rammer oring or the valve spool oring, and if it persists then you know its the valve seal (cup seal) or the forward rammer sleeve oring.