February 13th, 2015, 07:47 PM
Join Date: Nov 2007
Location: Frostbite Falls
Obviously Elmer hadn't seen it before either, since he is making an educated guess. The problem I have with it is that the op rod guide is installed very precisely on NM rifles by 1.) knurling the boss on the barrel then 2.) a press/hammer fit of the guide to barrel and 3.) a roll pin is installed in the hole in guide which slides into a corresponding slot on the underside of the barrel. Properly done it is a virtual impossiblity for the guide to turn. That is straight out of the AMTU manual on accurizing the M14. The M14 was an issue weapon when I served in the '60's and I never heard of that problem. So I would think this is an ideal solution to a non-existent problem as long as the guide is installed properly. In this case the entire assembly is made of aluminum, including the guide itself and it may be one piece but it doesn't appear to be. Aluminum would have a far greater opportunity to turn than steel on a knurled barrel boss - being softer and more pliable. That may be why no one, so far, has indicated they've seen this modification before. Having said that however, if the armorer who did it, didn't have the appropriate tool to knurl the barrel boss properly, this may have been a good solution at the time. In that case, I would expect that we would see it again in the future as more rifles come to light.
These photos illustrate the knurling and assembly I mentioned. The first is a near new M21 barrel that is medium heavy and you will notice the knurling under the edge of the rod guide. The second is a SAK NM barrel that is a take off and you can see the remains of the knurling and the groove that the roll pin goes into once the guide is installed.
Last edited by flintsghost; February 13th, 2015 at 10:04 PM.
Reason: add photo's