You don't " season " steel barrels, no matter what else you have been told. Only Cast Iron season. Always clean the barrel down to bare metal, then oil for storing to prevent rust.
If you have stored the gun standing on its buttplate, Upright, then oil is going to get back into that darn powder chamber, and through the Too-Small hole there into the very narrow flash channel. If the gun sits too long, the oil will congeal, and even firing several caps is NOT going to get it out. You need to use alcohol to soak the barrel, and the powder chamber, and that flash channel, to dissolve the grease and oils there. Most of us learn to remove both the nipple, and the clean out screw to run a pipe cleaner into the flash channel with alcohol on it, to really get the oil out. An undersized bore brush or scraper is often needed to clean those powder chambers, although a good, LONG, soaking with alcohol usually will clean them out fairly well. Just plug the nipple with a toothpick, or remove the nipple and plug the hole in the bolster with a whittled down stick, or small cork, before pouring the alcohol into the barrel. If the alcohol pours out looking like old urine, don't hesitate to flush the barrel a second and third time, or more, until the alcohol comes out clear.
If you decided to use an oil for any patch lube, DON'T use a petroleum based oil. Those oils don't mix well with black powder, and only burn partially. What is left behind is thick tars, that only get thicker, and really clog up the grooves and your barrel, not to even think what they do back in those powder chambers, and flash channels! Use a vegetable oil. The use of Olive Oil is a good choice( referred to back in the days as " sweet oil".) Ballistol works, which is based on mineral oil, a highly processed derivative of oil, that does not produce the tars that standard oils do. Jojoba oil, and any vegetable oil you have for cooking also work fine as patch lubes. However, IF YOU USE any oil as a patch lube, you should consider using a dry patch between the LUBED patch and your powder to keep the powder from being fouled by the oil. If you thin the oils down with water, to make them easier to spread on fabric, but dry out so that you have a " dry lube", as advocated by Dutch Schoultz,
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you can used the oil lubed patching on the range without experiencing most problems with powder being fouled by the oil. However, if you are loading that gun in the morning and hunting with it all day long, You will be better served by using a barrier between the powder and that PRB to keep the powder dry of the oil.