Yes it is, and it matters not a bit with regard to legal status in the US.
It also makes no sense, but the BATFE is the government entity that "decides" what is "controlled" and what is not.
The BATFE in their eminent wisdom have decided the frame of the luger is the controlled part, similar to the lower receiver/frame of the AR rifle.
The upper is not controlled in the US.
So the initial post is wrong, based on US rules and regs.
The post office, UPS, FedEx may make up their own rules as do many misinformed people.
But legally, in the US, (maybe some states have more rules), the upper is a part- as Ed said.
