Does anyone know the proper thread size, etc. for the Lyman 66 aperture sight? I want to get a smaller aperture for mine, but am not having much luck.... I've seen on the Lyman site that they list two... a hunting and a target.. but one is shown to be 1/2" and the other is 5/8"... I'm assuming they are talking about the overall diameter of the aperture body itself, and not the threaded part... and of course not the aperture opening... any ideas?