BSA R10 owners

I am curious what pellet shoots best out of your gun.. I know, I know all guns are different..
But instead of buying tins of all brands of pellets... I thought I would ask the 
people here and go from there...

I am trying to find the most accurate pellet for this R10..
So far I have had the best luck with JSB 18.3 

I can not help but feel there is something else that just might be a little 
more accurate.... Actually I went to size pellets last night
and was surprised to find that the JSBs that I am using are marked 5.5mm
and they mostly are .5.47 or smaller... So maybe just maybe ...there is something better...

MOD EDIT: MOVED TO PCP FORUM