Looks to me you have the wrong strategy altogether to create this.
I thought originally you were talking about a hand grip, like the gnurled one you might find on an old Thompson submachine gun. But you're having trouble with the
trigger.
Eliminate that whole area. Your trigger guard is nothing but a hollow tube (or cylinder) turned perpendicular to the cylinders you're using for the gun barrels, and there's a thin metal flange in it for the actual trigger itself. Any other object or part of the gun body that these protrude from can be made from a box, most likely, or a poly shape of their own.
