I know this has been asked before, but I can't find it. I inherited a shotgun from my brother-in-law, a Remington 870 Wingmaster, 2 3/4 shells only. I read somewhere that the correct way to measure the barrel length is to drop a dowel down the barrel (action closed), mark the dowel at the end of the barrel, and then measure the dowel to that mark. I measure 18 1/8" using this method. I want to make sure this is the proper method for determining legal length. Thanks!