I have a heavy refurbished 49. Blade bayonet, 45 degree gas port, forced matched bolt and receiver. Decided to try and move stock ferrule. A little dry lubricant, hammer and wrench it moved. On this one there is only a pin slot on top. This might indicate that at refurb, when changing over to blade and 45 degree gas block that they did a barrel change?? Alignment marks line up and there appears to be a 1 on receiver but not on barrel. Will take some pictures. I like to pictures outside but it is snowing.