I went to mount a March 3-24x52 FFP scope in a new set of 30mm ARC rings and it would not seat in the rings mounted very loosely on a Stiller 20 moa rail, nor would the rings fit the tube when off the rail. I then checked the ARC rings on 3 other brands of 30mm scopes and they fit perfectly. WTH? Not having a 2" mic, I measured the tube with 4 different calipers and after many measurements, came up with 30.1mm. Not a real accurate way to measure, but the tube is somewhat larger than 30mm. My question is "Has anyone running March scopes had this problem, heard of this or have a 2mm mic to measure their actual tube diameter?" I talked to Ted @ ARC and his thought was my March was slightly over true 30mm. Does anyone have an idea of March's tolerances?