I realise the heavier bullets might not stabilise but I've been trying for sub loads as well. Even a tiny load of 2.2gr. Red Dot pushes the 40gr. out at 1,500fps, hence trying the heavier ones, see what happens.
I know the 40gr group pretty well with 7.5gr Lilgun at about 2,250fps so I plan to try the 50's and 55's with the same load then I have something to compare them to.