hi Deano
the pellets that is best for it,is the one you get the tightest groups with at different ranges
in my AAS410K .177 i use AA field 4.52's,RWS super field's 4.52's.Falcon accuracy 4.52's.but i have stuck with RWS and only because of the amount of bad pellets i am getting to a tin at the moment from AA.
above is a small number of brand pellets that work well in the AA rifles,there are many others
H&N FTT
Accupel,
RWS super domes,
Bisley magnums,
H&N barracudda,
Webley Verminpel,
your best bet is to see if you could scrounge some test pellets from,the pellets swap