rgh25, we discuss this topic fairly often here because a lot of the guns we work on are old and may have been used in wet weather or neglected. If you use the search function here and do a search on "penetrating oil" or "frozen screws", you will find a ton of ideas and solutions. But the first recommendation I will make is to try something different than Kroil which has failed consistantly for me on really stubborn screws. If Kroil works, it probably wasn't all that frozen in my experience. Then I would advise great patience before resorting to brute force which will possibly ruin or break the screws, and before drilling them out. I've had numerous screws that resisted all efforts including various penetrating oils, heat, cold, vibration, etc., finally easily break free after several weeks or months of soaking. This is a good reason to have more than one project gun in the pipeline. You can move on to something else while frequently re-applying penetrating oil on your stubborn screw.
