Mossberg continues to innovate tactical shotgun design with their new 590RM Pump Shotgun. The “R” in the name refers to the ambidextrous rotary safety that gives the shotgun more AR-like ergonomics and handling features. The “M” refers to the 10-round detachable magazine that allows faster reloads.
Other key features include a Magpul pistol grip with a storage compartment in the grip, a buttstock adjustable for LOP, a recoil pad, and a heat shield over the barrel.
The model that I tested also features a Picatinny rail for mounting optics, adjustable Magpul MBUS3 two-piece pop-up sights, and a front M-Lok adapter by the take-down nut (the take-down nut is the part that would be known as the magazine cap in a 590 with a standard tubular magazine).
For those who train often with AR-pattern firearms, the familiarity and friendly ergonomics of the 590RM will be a real asset.
The manufacturer suggested retail price of the 590RM was $1,190 at the time of this writing.
Background
I grew up thinking that a cross-bolt safety was the most logical and natural version of the firearm safety. But for the owners of the 25 million or so AR-pattern firearms that are currently in the hands of civilian owners in the United States, the rotary safety may feel much more familiar. So when I read that Mossberg had introduced a version of the 590 with a rotary safety, I wanted to take a closer look. The fact that the rotary safety was also available in a magazine-fed version was doubly interesting.
I contacted Mossberg to see if they could loan me a sample for testing and evaluation. They were kind enough to agree. I eventually received an email with a tracking number. When I saw that the 590RM had been delivered to the gun store that handles my firearm transactions, I made my way there to pick it up.
First Impressions
The box contained miscellaneous paperwork; a 10 round magazine; a plastic bag with a cable lock; the manual; an NSSF brochure on safe storage; another NSSF brochure on firearm safety; an NRA membership application; a Mossberg decal; and the shotgun in a plastic bag. Mossberg had also sent me a second magazine via a separate shipment.
The 590RM has a definite tacticool vibe going on with a heat-shield over the barrel, AR ergonomics, black furniture, an optics rail with flip-up sights, an adjustable buttstock, and a hefty magazine slung below the receiver. The magazine inserts more like an AK magazine than an AR magazine as it has a catch in the front and rocks back into place, there to be held by a latch in front of the trigger guard. Since I spend more time with AKs than with ARs, that style of magazine insertion felt quite natural for me.
Fit and finish were excellent, the shotgun balanced nicely, and the trigger pulled smoothly and broke crisply.
Trigger Pull Weight
I took five separate measurement of trigger pull weight using a digital trigger pull weight gauge. My readings ranged from a low of 5.41 pounds to a high of 7.17 pounds, with an average of 6.13 and a median of 5.71.
Reading the Manual
The manual is 32 pages long, including the front and back covers. Here are some of the highlights:
It begins with safety warnings. This is good, because the purchaser may be a first-time gun owner who is unfamiliar with the safe handling of firearms.
Pages 4-7 are dedicated to mandated state-by-state warnings. I recommend moving these to the back of the manual since they are boring and repetitive.
The 590RM has a 2 ¾ inch chamber.
There is a helpful note on the handling of squibs on page 15.
The disassembly instructions are well-written and clear.
They recommend cleaning the firearm after every 200 rounds.
It is important not to pull the trigger while the trigger assembly housing is removed from the receiver. The falling hammer my cause injury or damage the receiver.
There is an excellent section on function testing.
For removing the heat-shield, the manual recommends using a “properly fitting wrench key.” It would be more helpful to specify which size wrench key should be used.
The shotgun is designed to accept choke tubes, which is a nice touch. The preinstalled choke tube with which it is shipped is cylinder bore.
It is nice that most Accu-Choke tubes can be used with steel shot.
“Lead, steel, and other non-toxic shot patterns will vary substantially depending on shotshell length, shot size, brand of ammunition, and the individual barrel. The shooter is urged to conduct pattern tests before field use.” This is excellent advice.
The warranty is for five years, and covers material and manufacturing defects.
There is a good parts list and exploded view.
There is also gun safety information on the back cover. This is a good location, visibility-wise. It summarizes the information on pages 2-3.
At the Range
It was a sunny and breezy day in late spring. The temperature was 75 degrees Fahrenheit and climbing. The birds were singing. There was no sign of the tornadoes that had touched down in the area the night before.
I made my way to the makeshift range behind the pole barn. I set up a target stand in front of the backstop, and a table with a Lead Sled 25 yards away. The first mosquitoes of spring were starting to make their presence known. They were still few enough in number that I was able to ignore them with some success.
I loaded a single round of Wolf Performance Ammunition 2 ¾ inch 1 1/8 ounce rifled slug. I centered the pop-up peep sight on the center target on the target stand and fired. The shot was on paper.
I then fired three-shot groups using the Wolf ammo as well as Remington 2 ¾ inch 1 ounce rifled slugs. The Wolf ammo tended to group at about 4.25 inches while the Remington ammo tended to group at around 2.25 inches. I was not surprised by the poor performance of the Wolf ammo, since I have experienced similar results while testing other shotguns.
I also patterned the 590RM using my Dad’s reloads consisting of 1 3/8 ounces of number 6 shot. Like most firearms manufacturers, Mossberg is not enthusiastic about the use of reloaded ammunition, and any damage caused by the reloads is not covered under the warranty. But I like to shoot some of my Dad’s ammo every now and then in his honor. And I am happy to report that Dad’s reloads did not damage the shotgun.
From 15 yards, the 590RM patterned at 22 inches. According to Jack O’Connor’s Complete Book of Rifles & Shotguns, this is a little tighter than would be expected. He would put cylinder bore at 26 inches and improved cylinder at 20 inches from 15 yards. The slightly-tighter-than-expected pattern is probably due to improvements in shotshell design since O’Connor’s book was published in 1961. I have noticed in my shotgun testing that they almost invariably produce a pattern that is tighter than O’Connor would predict.
As I mentioned above, Mossberg had provided me with a total of two magazines for testing. I loaded both of them and then cycled the ammo through the firearm. I could only load nine rounds in each of the magazines instead of ten. In both magazines, the spring was so stiff that attempting to load a tenth round resulted in the brass of the ninth round becoming dented by the rim of the tenth round. Over time it is likely that the springs in the magazines will relax enough to allow for the loading of a tenth round. For now, both magazines are effectively nine-round magazines.
Both magazines cycled well, and magazine changes were quick and easy.
Final Cleaning
Following the range session, I made my way to the kitchen table, where I put out a cleaning mat and proceeded to clean the 590RM. I removed the barrel and then scrubbed the bore with a brass brush. Then I ran solvent patches through the barrel until they came through clean, followed by a dry patch and then a CLP patch.
I repeated the solvent patch, dry patch, CLP patch process on the other accessible metal surfaces. I then reassembled the shotgun, gave the exterior a final wipe down, and put the gun away. It was now ready to be shipped back to Mossberg.
Conclusions
The Mossberg 590RM is an excellent tactical shotgun, with good craftsmanship, excellent balance, and a good trigger. The ambidextrous rotary safety is a great asset for those who are used to AR pattern firearms.
A red dot sight on the picatinny rail would allow for faster target acquisition than the pop-up peep sights that came preinstalled on the version that I tested. But it is great to have a set of backup sights that are not dependent on a battery to operate.
I seriously considered purchasing the test sample of the 590RM that I used in preparing this review. That would be a rare event. Out of all the firearms that I have reviewed on SurvivalBlog, I have only purchased two test samples to date. Ultimately, it was the gun’s detachable magazine that made me decide not to make the purchase. I found the big magazine hanging below the receiver to be awkward while handling the firearm. I prefer the traditional tubular magazine on a shotgun. I may give the 590R a try instead.
Disclaimer
Mossberg provided me with a sample of their 590RM Pump Shotgun for testing and evaluation. I tried not to allow their kindness to interfere with my objectivity as I evaluated the shotgun, and I believe that I succeeded. I did not receive any other financial or other inducement to mention any vendor, product, or service in this article.
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