Complete barrel fitting info can be found in the FAQs. There are other things to check besides how it locks up, headspace, barrel to frame gap and latch engagement, in that order. If it's lose ONLY when open, the spacer on wood forends can be shimmed to tighten it up. Sorry Marv, but The old H&R would fit a barrel IF they had enough underlug to cut it to fit, that would be if it wouldn't close all the way, if the underlug pivot is already too short they won't shim it. What they'll do under Remington's control is unknown. Westtexan, read the Accessory Barrel thread down the page or in the FAQs, turn around times stated by the current CS are mentioned by several members that have called CS.
Tim