Oh, OK, now I see the trigger forward of the handle...
Try this:
Create a set of vertices that represent the edge of your hole (from a disk)... move them in proper proximity to the outer surfaces of the object you want to place the hole in (one set on both sides)... then remove the outer surfaces of the solid handle object, and in Vertice mode, recreate that outer surface, also incorporating vertices of the hole...at some point, merge all three objects, (the original handle and the two hole shapes) into one object to cut down on annoying dialogue boxes.
This creates a much "cleaner" surface, reduces polys, too. It's simply much more time consuming than a boolean. But in many cases, it'll look a lot better.