Ruger Open Action Gun Lock

Graphite is unlikely to help, especially if you put in too much.

WD40, or TriFlo or one of its cousins, might help.

Then it probably is too snug. Either that, or there's crud in the lock, which the WD40 may help you determine. Or the lock is malfunctioning, or just plain binding, though I think you could tell the difference.

not completely sure, but I believe that there was a Corbin blank (don't remember the number) that worked much better in those ? we usually try to get the customer to replace those with a double locking pad-lock.

As soon as I stuck a blank key in

Whack the lock against the end grain of a 2X4 this might unstick the pin. any kind of solventy lube and or carb cleaner might help flush the crud out.

Scrap the lock if your attempts to free the pin are unsuccessful. To do more would require drilling a small hole above the first spring chamber and either removing the hole plug or using a stiff wire to free the jam. IMO not worth the effort on a $2 POS Chinese padlock.