NH here and I work in MA.. My Co. says, No Weapons allowed on Company premises. Therefore I do not carry in the building but I leave the firearm locked in the car. Parking lot is not owned by the Company. My Company is worldwide but where I am there are only 8 of us at this branch. I HAVE brought my firearm into the building and left it in my jacket (it's now in the car). I'm off the "clock" at 4p.m., but the office is open till 5. If I had to go back to work for something I forgot, I would be carrying........but concealed (MA.). I see your point about being off the clock and going in as a "Customer". And I do not see a problem with it. The rule as you explained it was for employee's not for Customers. That would be my argument should something come about of it. As a Customer, if there was a sign on the establishment then I would have to adhere to it. I do not know the Rules Of Conduct at McD's nor do I know how their set-up is for dressing room etc. If You're comfortable wearing it at work, then keep it CONCEALED and DO NOT tell ANYONE at work as someone on here already mentioned. If You're not comfortable wearing it, then I do not see a problem keeping it in the vehicle since You mentioned it's a large parking lot with other businesess which means McD's does not own the parking lot(I'm sure They pay rent on a part of it but does not mean it is in Their name). With that being said, I would still use discretion when out at your vehicle because Others do not know who You are or what You are doing. All and all, my Company does not allow it but I have brought it in (not wearing it; can't for the type work I do), and now I leave it in the vehicle, and if I went back into the building on MY time it would be Concealed anyway. If You got caught with it on Company time, the worst that can happen is You getting fired OR Maybe just a speaking to by your immediate Supervisor. shhhhhhhhhhhhhhh............
Just MY opinion.
(others please chime in if I'm incorrect on the parking lot ownership thing)
(All the above are MY opinions/suggestions ONLY....AND, I like to bust ball's, it's called having a sense of humor. In other words, no intent to offend anyone, so get over it)