I can't take exception to any comment here...all are good advice. Most important, as noted, is to clean the load bearing (hinge pin) and friction surfaces (locking bolt) and apply a new light coating of lube before each outing. Just like changing the oil in your car it's cheap insurance against damage!
I've used STOS from P/W for years (still do), but also use Tri-Flow Synthetic Grease at the recommendation of Giacomo Arrighini (Mr. Perazzi in NY). Good for the threads on choke tubes too. Both Tri Flow and STOS are easy to apply, and easy to clean off after shooting.
The labeling on the Tri-Flow tube is a hoot - "Acceptable for use in Federally inspected meat and poultry plants" and is Kosher Approved...important I suppose for those who are only allowed to shoot Kosher meats and clay targets. A three ounce tube will easily last for 2 years of weekly shooting. Remember, a clean gun is a happy gun. Good shooting to all.
