Similar to above comments ...
I have some Daystate Lis which are supposedly Prems from a single Die. I also have some Prems that Amac kindly gave to me.
Both pellets similar in size ... which is enormous ... and you have to push hard to get them in the HW77.
They were very accurate in the 77 up to 30 to 35 yards but then the slightest wind seemed to blow them about and groups were poor at 40 and 45 yards compared to 8.4gr JSB/AA.
I've tried them in a BSA S10 barrel but only at short ranges ... 15 yards up the garden. This S10 barrel doesn't like anything other than 10.6gr Bis Mags normally but it did keep putting 5 pellets of Prems 7.9gr through the very same 0.177 hole at 15 yards ... but that's only 15 yards. Not tried it at longer ranges yet. When I push a 4.52 JB/AA pellet through the BSA barrel they basically fall through ( I suppose the thin tails will open up under pressure ) but these larger Prems seem to push through tighter so maybe they will suit this barrel. Won't know until I've tried them at range.