Yes, the semi-autos get some sharp edges. Reaching in there is uncalled for guys. Go to any auto parts store and get a can of "Cyclo, Parts and Break Cleaner" It is under pressure and use it to blast out the receiver. It evaporates away but if you have an air compressor finish it off with that to speed it up. Yes, same stuff as "Gun Blast" but 1/2 the cost and the can is twice as big. No more cut fingers. I also use it to blast out the trigger plate assembly, bolt assembly and any where gunk can build up on a weapon. Good stuff. I use a case or so a month in my shop. Oh, don't get this stuff in your eyes as I can tell you it stings like hell.