The gun distributors would likely (and with good reason) boycott the manufacturers who are competing with them.
Do you feel that's a realistic possibility or strategy? Just saying (and I agree it is unlikely for the near future) Glock, Ruger, S&W, Colt, Remington, Mossberg, or another big-name manufacturer decided to go to retail sales, would the distributors stand a chance of improving their situation by boycotting that manufacturer?
It's not like there are hundreds of arms manufacturers and/or that all of them are putting out roughly equal products. In the public's eye, guns are the ultimate non-generic item. Brand is
everything. If a distributor boycotts them, the dealers (and public) will simply go around him to get the product they want. If the distributor pushes his dealers to boycott as well, the one lonely dealer who refuses to boycott becomes busier than he's ever been before because everyone who wants a Colt, or wants a S&W M&P, or whatever, comes to his door. A Pepsi sure may not be as good as a Coke, but if a Coke's not available, most folks will drink a Pepsi. If someone wants an M&P 9 times out of 10, they will travel a long road to get one -- not settle for the Glock that's sitting on the dealer's shelf.
If we were talking about ballpoint pens or car tires or even brands of soda I'd say such pressure would be effective. But guns are perceived as far more iconic and unique than that (and than they truly
are, to be honest). I'm fairly certain that S&W or some other major entity like that could absolutely dictate terms to their distributors without fear of repercussions.
To my way of thinking, previous posters are right in that the manufacturers use a distributor network because they WANT to. It outsources a lot of burden and cost in the dealing and distributing of their product.