Thanks, since my post I reached out to BA and they said they've never contracted with S&W for barrels. I purchased my rifle used on GunBroker so I guess it had a barrel swap sometime. That wasn't mentioned in the listing and it had the OEM pinned Vortex flashider so I wouldn't have ever suspected it. Not too upset about it though because I got it cheap, it's accurate, has proved reliable, and by all accounts I've found BA makes great barrels.
Still have it ... upgraded with a BCM® Bolt Carrier Group & Aero Precision - AR-15 BREACH Ambi Charging Handle with Large Lever
Zero problems.