Haha!
I think it would come down to the officer you are dealing with as to whether or not you might get charged. As defined by federal law (and as others have pointed out), a "firearm" is the part with the serial number (almost always the frame).
If I was to deal with you while I was at work, I would give you brownie points for disassembling it and have you run out to your car and lock it up and I'd get out of your hair. But I'm not every officer. I'm very gun friendly (better said - very responsible gun owner-friendly).
INAL, but my advice would be-
Lock the frame in your car, throw the barrel, slide, whatever else you want in your pocket, and go on about your business in whatever establishment you please. It's not worth risking everything that could result from a charge.