Re: How to make a dummy round for gunsmith?
Yes. But before you dump it on him do a bit of measuring yourself. You may find your idea requires a 'special' reamer and not just a throating reamer to lengthen the throat. Go to the SAAMI web site for chamber and cartidge drawings and dimentions. A dial caliper is enough tool for your measuring.
"Shoots real good!": definition; it didn't blow-up in my face.