How to clean sand out of AR

[sniper7]

You have one? How do you like it? AR-15 uppers are good, but not lowers, right? No Aluminum?

What is an areare-15 upper receiver made of?

[mcantar18c]

What is an areare-15 upper receiver made of?

Evil. They're made of racist evil.

As for lube...
In normal conditions, some light grease (something that won't run) on the contact areas of the BCG, the contact areas of the bolt, and a little itty bitty bit on the buffer and the hammer face.
In dirty environments, spray-on dry lube on everything.
In humid environments, lube with grass as above, then get your hands a little greasy and run your hand over everything steel... better to clean a little grease off your uniform than spend an hour scrubbing rust off your FSP after a week in the field.