Came across this write up on the Mossberg 590A1 from Frank Jardim.
If you do your bird hunting with a classic Mossberg 500 shotgun, you might be taken aback when you first handle their tactically oriented, nine-shot, bayonet-lug- and aperture-sight-equipped Magpul series Model 590A1. For starters, the 590A1 is built for war, not sport, and the Magpul series takes it a step beyond with furniture that enhances its tactical function and allows for more user customization than the standard military stock. Whether you're repelled by it or drawn to it, you have to admit: it's a sexy beast. At nearly 8.5 pounds empty, I found this model's weight alone impressive. It's a load to carry, which means any Marine Corps infantryman issued one will curse it long and loudly, but when it comes time to shoot it, that mass just soaks up the recoil of the heaviest 3-inch magnum loads.
This is a gun you can shoot slugs with all day long. I don't love this gun, but it's an apocalypse-grade weapon. If I have to go into battle against a rival warlord or endure decades of chaos after the collapse of civilization with just a shotgun, this is the one I'd want.
FOR THOSE UNFAMILIAR with the 590A1, it is the latest, and possibly final, tactical evolution of Mossberg's 500 series shotgun line introduced in 1960. The 500 series shotgun is one of the most successful sporting arms in history with over 12 million produced in various gauges and configurations.
The Mossberg 500 in tactical trappings was also very popular with law enforcement, but its most demanding role was serving in the hands of our military service members in combat in Iraq and Afghanistan. In fact, the changes that evolved the series 500 into the current 590 and 590A1 tactical shotguns were in response to the military's requirements.
Though non-NFA versions of the 590A1 with barrels 18.5 inches or longer became available to civilians in 2009, these shotguns are marketed primarily to law enforcement and military agencies. The 590A1 is among the mix of shotgun models and types the military currently uses for interior guard duty, prison security, riot control, door-breaching, boarding hostile naval vessels and front-line combat roles.
However, in the big picture, the shotgun is a specialty weapon and makes up a very tiny percentage of our military small arms inventory. Shotguns have served our troops most famously in the trenches of World War I, and the jungle fighting in the Pacific Theater in World War II and the Vietnam War, but always in small numbers. Unlike military service rifles, which are designed as combat arms from the first blueprint, shotguns and their ammunition were always selected and procured from normal civilian commercial sources, sometimes with no modifications whatsoever, other than the addition of martial markings.
GETTING BACK TO the specific tactical adaptions of the Mossberg shotguns, the principal difference between the 500 and 590 was the design of the magazine tube and barrel mounting. The former's magazine tube is closed at the end with a threaded hole in the center to attach the barrel. The latter uses an open-ended magazine tube with exterior threads and holds the barrel in place with a screw-on cap.
This made the 590's magazine much easier to clean. That wasn't a big deal for most American hunters, but it was for airmen, soldiers and marines, who tended to get a lot of sand and dust in their guns doing their duty during the Gulf Wars and the Global War on Terrorism. The 590A1 differs from the 590 in the thickness of its barrel and its use of aluminum, rather than polymer, for the triggerguard assembly and safety. It doesn't take too much to dent a shotgun barrel, and the U.S. Navy requested a heavier barrel that was more resistant to denting after observing guns were sometimes damaged banging into ship hatchways.
Read the rest of Mossberg 5091 Magpul here.