I was shooting with a bloke last year who had an M14...and I mean an M14 NM, not a civvie M1A. It was on a Winchester reciever with an extra heavy barrel...it was a real lump of wood & iron. First 'real' one I've ever seen...he said he'd got another one at home...on a TRW reciever.
Sadly "gizzit" didn't work...even tried it three times in rapid succession.
Did two for me (AR15 & M14 'Peerless') but charged me an extra $100 for NOT drilling the gas hole in the barrel (But they did say that they normally bought their barrels in pre-drilled so it was a special request.) I had to get another outfit to handle the export.