I simply do not OC in the Billings area. I have no need to OC. If I go into a restraunt that 'serves' I take my piece out of my pocket and place it in a piece of "luggage" (my wife often has a piece in her purse). Basically, Ionly carry for reasons of self defense (against nasty critters - both two legged and four legged) and I really don't care to share the fact that I am armed with any "punk".
I have noticed people (that I do not know) OC in the Billings area, but the occurrence is like a million to one.)
I do OC (quite frequently) when in the back country - both side arm and carbine. Related to that, I have OC's my SA in the Red Lodge/Columbus/Big Timber area - mainly because I choose not to leave it in my vehicle. (I can conveniently secure my carbine.) I have never been 'stopped' by aLEO while OCingin 'town'. I have had several OC interactions with LEO's (SO Deputy's & FS LEO's) outside of town, ALL WITHOUT a problem. The most noteable one is described below...
In Aug 2008 we were making our way back from very liberal NW MT (a.k.a. 'enemy territory') with the RV. We had never been to Sealy Lake, so we pulled into one of the NFS campgrounds. We were 'set-up' when a volenteer 'host' dressed as RANGER RICK (serriously this guy wantedanyone who saw him to think he was a real-live FR), and told us there was a cougar seen in the campground. I thanked him and told him I'd be on the 'look out' with my .357 Mag.at my side. Right then, (Comiefornian) Ranger Rick went ballistic and started to lecture me about carrying a gun. I let him speak his piece, thanked him again, and went into the RV (to get my Blackhawk) and he left. About 45 min later a FS LEO came by, stopped (only) at our campsite, walked up & asked is "everything was alright". (by then I was wearing the Blackhawk). I Told him that one of the volenteer Hosts had informed us about the cougar. He then told me it was against FS regulations to discharge a weapon in a CG. I replied that I was aware of and understood the FS regs in that regard, but that if I was attacked or threatened by the cougar I would defend myself and my party as appropriate. He then thanked me for my time, got into his Partol Car and left.
Never saw or heard the cougar that night!