You can use multiple uppers. The length on the form should be used for the "most" used one, though I would probably just put the shortest one on the form but it doesn't really matter.On this note, for an AR lower would you only be able to have one upper? So I couldn't use my 7.5" and 10" upper?
The OL is the length with the stock unfolded measured parallel with the bore. Do not include removable muzzle attachments.Overall length, is this the shortest possible length the rifle can be? (Stock folded) or
Is OL the longest possible length, end of barrel to end of extended stock?