When a seller realizes they've been caught trying to hide a major quality error by a savvy buyer, who will likely return the gun after expensive shipping to him, and risking further damage going back and forth, the obvious thing to do is to cut your losses. That's what it sounds like the seller did, without an apology or any discussion about options to make it right (another rifle, or a discount on this one). He "made it right"... for HIM! Not for the potential buyer he was trying to screw. Just ready to move on to another buyer, without a "beg your pardon..."
No comms saying "oh, I'm sorry, you're right, how about if I refund your money?" Instead he throws the money back over the bar and walks out. I wouldn't buy from this kind of person again.