Okay, than 3" chambers won't be that much of a challenge. I would suggest you go with a 20ga (I'll be stepping on some toes here!) They make 28ga 3" loads with a max payload of 1 1/16oz of shot. A 20ga 3" payload will be 1 1/4oz. So if you want a heavier payload, 20 is the way to go. Remember you can shoot 2 3/4" loads in a 3" chamber with no problems.

You should have no problem finding a good O/U with 3" chambers and in a SxS some of the top tier Spanish makers have 20ga guns with 3" chambers. If you want one built like a tank as you said, then have a look at the older Merkel models. Such as:

https://www.gunsinternational.com/guns-f...un_id=100922167

Your best bet is to go on GI and look thru the various makers, you should be able to find something that tickles your fancy.

https://www.gunsinternational.com/guns-for-sale-online/shotguns-for-sale.cfm?gid=6

and specific 20ga SL guns

https://www.gunsinternational.com/search-results.cfm?cdn_bp=1&search_term=20ga,Side,Lock&qs_cat=Shotguns&page=1

Half the fun is looking! If you find one, let us know and we can be more help in making a recommendation.

Best of luck to you!

Greg

Gregory J. Westberg
MSG, USA
Ret