bobstreit:
There are no stupid questions just the occasional stupid answer.
"bbl" usually means barrel and "bb" can either stand for bulletin board or a shot size that is larger than the numbered shot but smaller than buckshot. I've only put slugs through three over/unders and two sxs and the o/us were slightly better but I think this will vary from gun to gun. Interestingly, all of these guns were reasonably well regulated with shot. If you get either that will put two slugs into a one foot circle at 25 yards, you will have done better than me.
As for learning about shotguns, I am reminded of the time an acquaintance who is very knowledgeable on shotguns was asked how he learned so much. His response was, "Because I don't golf."
Shotguns are my passion, rifles are an interest and handguns are a necessary evil - if there wasn't evil in the world they wouldn't be necessary.
What I have learned about shotguns has come through a willingness to ask questions (no matter how mundane) to those who know more (that's a lot of people) combined with a willingness to try just about anything.
Reading helps a lot. Some years back I got taken on a gun deal and I mean hosed right down to my skivvies. It wasn't a lot of money but I vowed that I wouldn't let that happen again and over the years have invested in a good library of books on guns. The cost of the books has exceeded the original loss many times over but I've surely avoided some bad deals as a result.
I will not turn down a chance to shoot any gun, anywhere, any time. The Grand in Vandalia is a particular delight because you can borrow/rent different guns. I've been lucky enough to shoot beaters that disassembled themselves when fired with heavy loads right up to handmade English sidelocks worth more than many houses. By the same token, anyone who shows an interest in any of my guns is offered the chance to give it a try.
I have never earned my living from or with guns. Those who have seen me shoot would agree that I shouldn't give up my day job.
And I don't golf.