I have an FFl do I need a MFG licence to put differant uppers on lowers?
ie: If a customer wanted me to build (I am a Colt M16 Armorer) a custom lowere with a match trigger group and place a 24" free float barrel on top. Do I need a Manufacturers Licence?

Thanks

As far as I know, the manufacturing is the forging or casting of the lower reciever and giving it a serial number.  You would not be manufacturing a rifle.

If you are purchasing lowers only (as opposed to complete firearms) and assembling them with uppers for resale, then you are engaging in assembling, which IS considered manufacturing by the ATF.

If you buy only complete rifles, and then swap parts around on them, that is not manufacturing.

The reason is that a manufacturer must pay excise tax on complete firearms sold, but not on incomplete receivers.  So when you go buy a stripped lower, or lower-only, there has been no excise tax paid on it.  The first licensed manufacturer who builds it into a complete firearm owes tax on the sale price.

An unlicensed person doesn't owe the tax, provided they're not engaging in the assembly of rifles from lowers and uppers for sale, which would constitute both dealing and manufacturing without a license.