For you guys that have nice scopes on your AR's…especially 1-4x and 1-6x scopes…do you always remove your scopes from the upper before you get into the cleaning or do you leave it on and just get after it?  If you leave it on, what precautions do you take to make sure the scope doesn't get damaged?  I would imagine you would want to separate the upper totally as just the back pin out and the upper swing around with the weight of that scope would just be a recipe for disaster.

Leave it on, even if you have a good QD mount that will return to zero.  You won't actually know if it did return to zero till you shoot it again.

Buy some butler creek scope caps and close them while you are cleaning, problem solved.

Leave it on guys with bolt action rifles that have optics don't remove them when they clean their rifles what would be the purpose of taking it off on an AR?

I don't have a scope on my AR yet, trying to work back to old school irons but with my M1A Scout I have a 1-4 Leu scout scope with QR rings and usually always take it off to clean and the return to zero does change very little but at the range I always pull it off to shoot with the irons that's why I put QR rings on it. YMMV

Pop the pins out with a little hammer and punch while it's completely supported on a towel covered workbench.   Pick up the upper and wrap the scope in a plastic grocery bag using a rubber band to keep the bottom closed.  Run a wet patch or boresnake through, and put some CLP on the lugs.  Set it aside (far away from you) while you concentrate on the lower.  Set the lower aside and carefully return the upper to your work area.  Finish bore and chamber cleaning.  Reassemble the upper and lower.  Take bag off scope, clean lenses with soft brush and paper towel with windex.  Drink a beer and admire your attention to detail.

Leave it on.

I now clean with a jig that holds the upper and lower apart at a predertmined angle.

Look at this

Best for use with a bipod though.

Only time I take my scope off is when I do a complete teardown and remove the handguard to CLP the barrel & gas tube.  The scope protrudes enough to prevent the top half of the guard from releasing from the delta ring.

Whatever it is you end up doing, do not get any lubricants or solvents on your glass. You should have a brush that is only for use on your glass and never comes into contact with any solvents or lubs.