August 24, 2020
By Leroy Thompson
There’s something about martial shotguns in trench gun configuration that has always attracted me. They have both aesthetic and practical appeal. I like their look with the ventilated hand guard and bayonet lug. They conjure images of close combat from World War I to Vietnam and even to the War on Terror. Practically, I feel that the ability to mount a bayonet on a home defense/preparedness shotgun has no downside. A bayonet doesn’t have to be mounted, but in civil unrest or disaster when looting becomes endemic, a combat shotgun is discouraging to bad actors, but a combat shotgun with a bayonet is ever more discouraging. Psychologically, a lot of scumbags will figure you probably won’t shoot them if they don’t have a firearm, but they may think you’ll stick them!
By the way, the ventilated hand guard on trench shotguns is not just to make them look more deadly. The thinking was that after firing a few rounds of buckshot at an enemy, the weapon’s barrel would become hot making it difficult for the soldier to grasp the forward portion of the barrel for a bayonet thrust. The ventilated hand guard was intended to allow a grasping point.
I acquired a Mossberg 590A1 shortly after it was introduced because I was impressed with its performance in military trials. Of shotguns tested, only the 590 passed all US military endurance testing. One of the most noteworthy features is its heavy barrel designed to stand up to multiple deployments and knocks on everything the soldier encounters. Other principal parts — trigger guard, safety, slide release, et. al. — are of aluminum rather than plastic. Its parkerized finish offers good corrosion resistance. Another advantage of the 590A1 from a military point of view is that the cap for the muzzle tube may be readily removed thus allowing the tube to be cleaned and the spring and follower to be removed for cleaning in harsh conditions. Although this feature may not seem important for the home defense shotgun, arguably it is a useful feature for a boat gun where thorough cleaning is periodically desirable.
From the ergonomics standpoint, the 590A1’s sliding safety atop the receiver is arguably faster for most users since the thumb may quickly push it forward without having to change the grip of the shooting hand. With the cross-bolt safety used on other combat shotguns, it may be necessary to change the position, though with practice, I’ve learned to shift my hand slightly and push the safety off with a trigger finger joint. Or, I push the cross-bolt safety through as the finger goes for the trigger. A more-clear advantage of the Mossberg safety is if the shotgun is fired off of the left shoulder the safety may be operated readily with the left thumb. The slide release may be operated with the middle finger of my shooting hand, while pulling the forearm to the rear.
Another feature I like on combat shotguns in general and the 590A1 specifically is the ghost ring rear sight. It’s fast when firing multiple rounds of buckshot on multiple targets but allows relatively precise aiming with slugs. Using slugs, I can shoot head shots on a silhouette target at 50 yards with ghost ring sights that are zeroed and can do good center of mass hits on a silhouette at 100 yards. The 590A1’s front ramped sight with red insert picks up really well for quick engagement and works well for more precise slug shooting. One note I’ll make about the ghost ring sights is that the Mossberg manual is not clear on adjusting them. To adjust elevation, a toothed wheel is rotated clockwise to lower the sights and counterclockwise to raise the sights. What the manual doesn’t state is that to accomplish this the fingers must be used to pull the ghost ring up while moving the wheel with the thumb. For adjusting windage a screw is turned clockwise to move the group/pattern right and counterclockwise to move the group/pattern left.
Another feature I like about the 590A1 Retro is its thick recoil pad. Combat shotguns in 12-gauge have noticeable recoil, one reason a lot of police departments stopped issuing them. There were too many complaints from inexperience and, often, small officers that shooting the shotgun hurt their shoulder. Of course, for decades, the police shotgun had also stopped a lot of felons from resisting arrest just by its display. That far outweighed a little recoil and if it had to be used it was a fight stopper. The 590A1’s recoil pad does a good job in mitigating that recoil. I fired at least 60 rounds of 12-gauge ammo in one session while testing the 590A1. At least half of those rounds were lower recoil “defense” loads but the other half were full-powered loads including some 3" Magnum loads. Normally, my shoulder would have shown some bruising but none was apparent and my shoulder was not stiff — well not any stiffer than usual from accumulated injuries over the years. Thank you, Mossberg!
The “Retrograde” portion of the 590A1 under review stems from its use of a walnut stock and forearm. I shoot shotguns with wood furniture and shotguns with polymer furniture and like both. Still, the military trench guns in my collection all have wood furniture so I see some nostalgia in the retro furniture. To be honest the primary features I evaluate with a combat shotgun stock and forearm are that the stock doesn’t slip in my hand and that the forearm offers a sure grip so I don’t short stroke when operating the action. The Retro’s walnut stock works fine, and the ribs of the forearm offer a sure grip.
I mentioned that I like the ability to mount a bayonet. I have a 590A1 I acquired a few years ago that came with an M9 bayonet. The 590A1 retro does not, but an M7 or M9 bayonet is easily acquired.
An M9 bayonet I had brought along locked onto the bayonet lug, though it was a tight fit and took some effort to get off. I plan to put a little lapping compound on the lug and put the bayonet on and off a few dozen times to work it in. Bayonets can affect harmonics on rifles. In fact, some Russian contacts told me a lot of Russian snipers liked to fire their Dragunovs with bayonet mounted as they felt it improved accuracy. I fired some patterns with buckshot at 20 yards with the bayonet on and off and noticed little difference. The 590A1’s thicker barrel probably dampens any effect. Still, when I get a chance I’ll try a 100-yard group using slugs with bayonet on and off.
As is typical of combat shotguns, the 590A1 Retro is choked cylinder bore. I fired my buckshot patterns primarily at 10 and 20 yards and found that they stayed tight. I did fire one 35-yard pattern of 12-¾" with Federal 3" 000 Buck. I will try longer shots next outing with the 590A1 Retro, but with my other 590A1 I generally get about 50% hits at 50 yards on a silhouette target.
I have done shotgun testing in the past on vehicles but didn’t have any cars to shoot up this time around. My experience, though, was that slugs were by far the most effective at engaging a target within a vehicle. Instead, I decided to do a drill based on one retired patrol officer friend who used to carry the first three rounds in his shotgun of #4 Buckshot, as he patrolled an urban area, followed by two slugs. Using a Threat Down target, at 10 yards, I fired the first three #4 Buck loads quickly center of mass, then fired the two slugs into the “head” of the target. As the photos will show the buckshot tore the center out of the torso, while the two slugs made sure in case I was dealing with an urban zombie!
Mossberg shotguns are proven with the US and more than 75 other countries’ armed forces and police. They are also proven with many thousands of Americans who keep them for home security. The 590A1 Retro offers the proven durability and reliability of the M500 and M590 models with the enhanced combat utility of a military “trench gun.” The ventilated hand guard, bayonet lug, extended magazine, and walnut furniture enhance its looks and also make it a formidable close combat weapon.
Mossberg 590A1 Retro Shotgun Specs
- Action: Pump
- Caliber: 12-Gauge, 3"
- Overall Length: 41"
- Barrel Length: 20" (Cylinder Bore)
- Weight: 7.25 lbs
- Cartridge Capacity: 8+1
- Rear Sights: Ghost Ring
- Front Sights: Ramp
- MSRP: $902
Mossberg 590A1 Retro Shotgun Performance