Most doubles have short chambers. Briley's often wants to lengthen the chambers for 20 tubes. The metal gets very thin if you try to use 20 2 3/4" tubes in a 2 5/8 or 2 1/2" chamber. Do not alter the chambers just to shoot tubes. You make your barrels into a set of carrier barrels that will/may not be safe to shoot the original shells in anymore.
Purist will hate tubes. They will point out that the barrels get heavy. You add a whole 10-12 ounces. Worse you can get screw in choke tubes. Do not pay any attention to them. Either shoot what you like or not. It is your choice. It is supposed to be fun not some form of proper manners.
If just shooting clay targets look at a set of 28 ga. companion tubes. Now I contend that shooting 28 or even .410 tubes will make your gun into a fun double to shoot. Easy on the stock and well capable of breaking clay targets. I rather shoot a gun than just own it and be afraid to shoot it.
I found a old set of Briley Match weight tube in 28 and .410 and cut them down to 20". I guess the 20 had cracked as only one 20 tube was with the set. Backbored .008 and .016 chokes in them. They predated Companion tubes. I have shot them in many guns over the years. After the Companions came out I bought a set of them and use them instead.
Just picked up a old set of Parabaugh 28 and .410 with extractors for Browning Superposed. Fitting them to a pre-war Super with double triggers. Going to shoot skeet with them this weekend. It is all about making these old guns safe to shoot and more fun to play with. I do try to do it in a manner which does not alter the guns too much for the next owner.
