So traditional gun makers are like the traditional "big-three" carmakers - stuck in their ways and often saddled with high overheads, unfunded pension liabilities, and intransigent unions. Newer, smaller companies - particularly from overseas - can make more modern firearms with higher capacity clips, and take away their business in a hurry. The Austrian-made Glock with its 15-round (standard) clip, has supplanted the old "1911" .45 automatic, which had a paltry 7 rounds or revolvers with their pathetic six rounds.
But one by one, the old-line gun makers have gone bankrupt - or nearly so. Smith and Wesson discovered the hard way that it doesn't pay to cross the NRA. Gun owners may be in the minority in the United States, but NRA members make up the majority of gun buyers. Then Colt, and now Remington. The pundits and journalists may opine that it is Trump causing a decline in gun sales that is triggering (sorry!) this wave of bankruptcies, but I think something else is at work here.
When you get right down to it, the firearms business is just a business like any other. And since competition is so fierce in this business, it is a tough business to make profits in, even when times are good and a Democrat is in the White House.