Don't know about whether they're ER Shaw seconds or not. Adams and Bennett is now owned by Midway USA, and sold out of their Columbia, MO facility. But that doesn't mean they don't have an underlying agreement with Shaw.
Have heard mixed reviews on A&B barrels. Are you looking at their Savage barrels? Or their Mausers? Or just a blank? It pains me to say it, as Midway is in my neck of the woods, but if you're looking at their Savage barrels for a rebarrel project, I'd go with a factory Savage barrel instead, as Savage factory barrels seem to always shoot. You can order Savage factory barrels at
www.savageparts.com for the same price as Midway sells A&B barrels.