ORIGINAL: doubleA
I too have had Briley Thinwall tubes installed on a couple of fixed choked target O/U's and while they perfrom very good, I would think getting a new Rem 870 barrel with Rem chokes would save you in the end. With the Rem choke type you have and endless array of aftermarket tubes while the Thinwallscan only be hadfrom Briley. Oj course each barrel is different and if your smith can cut a stanard threads in your barrel then that would probably be the most cost effective and easiest.
Unfortunately, Rem Chokes are not an option.According to thesmith atMann &Sonit wouldhave to be a thin wall system.
I am thinking about having Carlson (choketube.com)do the install. $85+ $15shippingfor install + 3 chokes. That way I'd have reasonably priced chokes available if I decided I needed more. They also seem to know what they are doing from the articles I've read about their company & products. According to their service dept, they can install on any barrel (20 ga) over .700 in diameter. Turn around is about 3-4 days.
Thanks for the responses.