I would have been in serious Dutch at the time, but I used to run almost boiling water through the lower of an M16 because I wasn't allowed to take it apart. Had the armorer scratching his head a lot and mad because he couldn't keep rejecting it for not being clean when I turned it back over to him. It worked wonders and never hurt the thing. Just rub off the water spots after it dries and no one will know.
I've never been a fan of dousing with lubes because it always seems to seep and drip and worse, collect grunge faster. A needle-like lube applicator, or a wire or toothpick can be used to put that stuff only where it needs to go. Even then, I waste more than I use because I sop up excess with a Q-Tip before it can run or drip where it shouldn't. At the time, when we still used LSA, they actually condoned dousing.