Hello again and I hope you are having a good day. I think I have some more help for you I went ahead and looked it up for where I saw that about a shotgun combat magazine tub extention for browning auto-5`s , I got out one of my old Shotgun News issues that I have and looked it up and found it. Looks like the name of the company is Quality Parts CO. they sell Bushmaster firearms and parts but they also sell other things like rifle and shotgun synthetic stocks and things of that nature.They also sell combat magazine tub extentions for pump action and semi-auto shotguns. Their web address is
http://www.bushmaster.com and their phone number is toll free 1-800-998-SWAT the numbers for swat if you do`nt want to look at the letters on your phone are 7928 their fax number is 1-207-892-8068 anyways you can get in touch with them and you could even request one of their 80 page catalogs free upon your request.
Another place you might could get in touch with that makes combat tub mag extentions that might work with the browning auto-5 would be Briley Manufacturing they have tub mag extention that i Know work with the browning gold and the winchester super x and benelli and remington shotguns so they might be able to help you with your browning auto-5. theit phone number is (713)932-6995 to ask for technical help like asking if they would have a tub mag extention for browning auto -5`s or maybe if they do`nt have one but maybe they could make you one all they would really need to do is make the tub and thread it right to mach up with the threads on the end of your tub mag after you tack the end cap off and then also of coarse have the rigth length of magazine spring and a good mag spring follower and then you are good to go.
Well anyways I think one of both of these places will more then likely be able to help you out and get you all set up nice and pretty .Hope this helps you out and get out there and ejoy shotting that browning auto -5 some more and pactice practice practice.The you get to have double the use out of a fine old shotgun you get to have fun practicing with it and if you have too hope you wont have to but if you had to use it to defend yourself and your family with it then you would more then be plenty prepared to handle the situation.
Have a good day and always try to be prepared.