The gauges I use are original military gauges except for one set of excellent headspace gauges that I kept from Graham at Arrowmark Tool and Gauge in Australia. I carried them as inventory here until he stopped producing them many years ago. You can easily make or have made a .310, .307 and .301. I'm told Forster has some custom made .074 No-Go headspace gauges available. Call them and ask for Scott. The .064 Go gauge is standard SAAMI also.