There are several ris units out there that will fit a large battery and a few that won't (jg ris will NOT fit any battery except a tiny lipo)
They all fit on the same. Just slip on the tabs and put the pin in.
Try to get a metal ris instead of the plastic as the rails can be pulled off the plastic. Not easily, but it can happen.
Your silencer adaptor is 14mm counterclockwise so the majority of silencers will go on without a problem. Stick with a short one.
Grand Poobah of T.W.A.T.