In our experience with RN45 feed problems it almost always has to do with the small piston on the side of the nose that moves the feed paw. Make sure all the parts and o-rings are in the cylinder properly and that the feed paw moves in its track freely. If you bought a rebuild kit it should show you how it goes together properly, if not go to www.ereplacementparts.com or http://servicenet.bostitch.com and search for your model number for a breakdown of your nailer and make sure the feed cylinder is assembled properly.