I understand and agree. And I like the idea of creating proof that it was built that way first. To play Devils advocate though someone can just take a picture of their lower with a friends upper.Of course this is true. However you will know you are lying. It is much harder to tell a lie consistantly. There is no proof that it was ever a pistol, other than your word. And maybe that you own a pistol upper. I take my word seriously, enough so that I actually did put a pistol upper on all my lowers before making a rifle. There are people on this forum that sent themselves certified letters with pictures of thier new lowers configured as pistols.
Granted it's "built" at that time.