briley is only threading for their chokes? this is because there probably isnt enough barrel wall thickness for perazzi style choke tubes. have you had your barrel thickness measured? Thinwall tubes is what it will probably only accept.
I have untouched factory barrels....bores .729.....choked .32 and .40. Barrel OD .810......it's got some different factory chokes than I've ever seen.....the taper runs 4" down to the parallel, which is 1" long to the muzzle. The guy at Briley came this close to calling me a liar.....but I've mic'd 'em many times.
Bore ID at about 2" in is about .715....so that makes wall thickness about .047 minimum.....060 max.
How about somebody mic the OD of your late model O/U barrels with factory tubes.
WGH, Perazzi Generation 2 chokes measure .805 OD. Generation 3 and Big Bore measure .825 OD.
I haven't figured out how to get them into a Barrel that measures .810 OD. It would look butt ugly when I got finished with the welder.
If you are attempting to raise the POI with choke tubes, don't.
I have spent too mush money making sure we install chokes true to the bore.
I will not put one in crooked.
Stu: I don't want the tubes installed eccentric.....I want the tubes installed normally (concentric), and the choke cut eccentric in the tube.....and if I'm going to put those nasty things in my barrel, I would prefer Perazzi tubes.
Still would like to know OD on gen.4 tubed barrels. Anybody?
WGH: my Perazzi MX-11 c/t bbls. measure .995" at the muzzle, .796 at forend, C/Ts have. 827" o.d. Hope that helps. In fact, Kolar made me an eccentric tube for the bottom bbl. out of a spare #10, opened up to.022 constriction. These are gen 4 18.4 tubes
Before I fiddled with these barrels talk to someone that regulates chokes as with what you are describing is probably the absolute best configuration you can get long taper then a parallel bore before exit as to changing the POI probably the only way to do this is to pull the barrels apart and alter the web between the barrels
with a backbore job, Eyster cane set the choke to shoot pretty much where you want it. I had a TM-1 once that he had b.bd to .736, and the choke was set so high that no one could hit anything with it, including me. I went to his shop on the way to a pigeon shoot and spent 4 hours and $195 to have him work it down to concentric with the bore, I lost about .006 constriction, still had .028, worked pretty good after that.