So with an AR, if I engrave the barrel, and have more than one upper, say a .33LR, a 5.56, and a .300 BO would I need to engrave all three ?
Yes, if the barrel length is below 16" and they will be mated with the registered lower. Anything that completes the SBR configuration of a barrel length under 16" must be marked.
Yes, if the barrel length is below 16" and they will be mated with the registered lower. Anything that completes the SBR configuration of a barrel length under 16" must be marked.
There is no such thing as a registered lower. Only complete rifles can be registered. If the barrel was marked for registration, a replacement barrel does not need to be marked however.