Heck of a tight budget and shooting 200 rounds over a 15 year period won't churn the buffer to butter. I suspect that Kerosene is the culprit. Ask your armorers to stay away from it and any non-gun care products.
Since WD40 leaves a film, it isn't ideal for firearms either. Remington was sued by a Texas man who shot himself when the safety failed. The safety failed because he used WD40 for over 20 years and the deposit grew so thick that it defeated the safety. When that rifle was placed in a vise, it took two large employees to separate the action from the stock (the owner never took the rifle apart to clean it). That's when Remington discovered the buildup of WD40. The jury felt sorry for the old man and held against Remington anyway (Sorry Rich, but after all, it's not their money). Good luck,