Bought this Knoxx stock and it said it would fit 12&20's. I was a little leary but decided to try it. A little above the receiver and a bit of a gap between the trigger and the stock. It is tight though. Is it ok to have the gap?
No, that's not correct. It should fit flush with no gap. Here's how it should fit!
(http://imageshack.us/a/img560/4580/20130312181758.jpg)
NO, none of the 12's fit the 20 unless it is an old old model with a different size receiver. Ebay is about your only chance to get the 20 ga model and get ready to bring your wallet to the table. I've seen them go for over $200.
(http://i1031.photobucket.com/albums/y372/Gophert/Hunting/DSC_1070.jpg) (http://s1031.photobucket.com/user/Gophert/media/Hunting/DSC_1070.jpg.html)