Most reamer makers also produce headspace guages, speak with the company that produced the reamer. I've not seen one around here but Josh may have one. He's usually on the forefront of the new wave.. If you can't find one I'll call and see if he's got one available. Where, if I may be so bold, did you happen upon the reamer? Who made it? what rifle configuration are you goin g to build? Long barrel, short? Keep us informed if you get the chance!! We appreciate the new info!!