Practical Shotguns: Mossberg's New 940 & 590 Thunder Ranch Series

Mossberg and Thunder Ranch collaborated to create two exceptional shotguns

February 14, 2025 By Patrick Sweeney

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For those who have not read their history, Clint Smith is a decorated marine who served in, and was wounded in, Vietnam. Post-war and working as a police officer in the Midwest, he attended Gunsite in the early years, and was good enough at teaching that he was offered a position there, quickly ending up as the Operations Manager of Gunsite. When it proved to not be possible to purchase Gunsite at the time Jeff Cooper was looking to retire, Clint opened his own range, in Texas and called it Thunder Ranch.

Mossberg 940 and 590 shotguns, ejection port view — The Mossberg Thunder Ranch Series, on top the 940 Pro, below the 590. (Photo Provided by Author)

Later, he moved his operation to Oregon, and has lived and taught there ever since. Clint is not one to teach how to win competitions, unless you consider saving your own life a competitive sport. In the course of his Vietnam and law enforcement experience, and teaching at Gunsite and Thunder Ranch, with a short stint setting up the training division of HK, he determined that solid, dependable, rugged gear was the baseline to work from. Competition fripperies were just that. So, when he puts the Thunder Ranch name and logo on something, you really need to pay attention. When the two boxes from Mossberg arrived, I was eager to see what was up. Let’s start with the pump, since that is such an iconic American tool.

Mossberg shotguns showing left side view — Both of the Thunder Ranch Mossbergs have barrels eighteen and a half inches long and are finished in Cerakote. But there’s a lot more different between them. (Photo Provided by Author)

Thunder Ranch 590

Thunder Ranch etching on receiver of shotgun — The side of the 590 is full of details. There’s the Thunder Ranch logo, of course. You can see the lifter pivot boss behind it, the trigger housing pin below it, and the shell stop pivot boss below the ejection port. (Photo Provided by Author)

I started 3-gun competition in the summer of 1981, with a Mossberg 500. (The rumors that when I first started shooting the Dead Sea was merely sick is just that, a rumor.) I found it handy, lightweight, and with features that were appealing. The 590 is all of that and more. The big change from the 500 to the 590 was the way the barrel attaches. On the 500, the barrel has its own bolt that screws into the end of the magazine tube. If you had a five-shot model (like the Mossberg 500 I had while I worked in Flint, MI back in the late Neolithic) you could not increase capacity. You either had to trade or sell your five-shot for the eight-shot, or you needed to replace the barrel and the magazine tube and its internals.

On the 590, Mossberg changed that. The barrel has a loop on the front that slides over the magazine tube, and there’s a magazine cap that screws down (onto the threaded magazine tube) over the loop. If you need more than the standard tube holds, replace the cap with an extended tube and a new spring. That is a lot easier.

Mossberg 590 magazine tube and front fiber optic sight — The 590 uses an open-ended magazine tube (with mag spring retainer inside of it) and a cap that also holds the barrel in place. That button on the end is a sling swivel stud. A red/orange fiber optic front bead makes keeping track of your aim a lot easier.(Photo Provided by Author)

However, the 590 retains the great features of the 500. First up is the lifter design. On other pumps, the lifter blocks the loading port. You have to push the lifter out of the way as you stuff a new shell in. If your finger slips, the shell pops out, and wedges itself between the lifter and the bolt. (This was a problem with the 870, one many of us fixed back then by modifying the lifter. Then Remington offered a modified lifter of its own.) On the Mossberg, if you don’t get the shell fully inserted past the shell stop, it pops back out but doesn’t wedge. You just shove it again, this time all the way.

The 500/590 does not have both its shell stops secured to the receiver. You might think this is a shortcoming, as you might lose the free one. Hey, if you easily lose one of the six-inch pieces of spring steel in cleaning your shotgun you might want to reconsider your choices.

Trigger assembly removed from receiver of 590 shotgun — To remove the trigger assembly you only have to push out the one pin and hinge the assembly down out of the receiver. Those other two details you see are not pins. Don’t hammer on them. (Photo Provided by Author)

The 500/590 uses dual action bars, so you get a low-friction pump action, as the possibility of the action binding is reduced to almost never. The trigger guard is a synthetic part, molded as one piece, with the hammer, trigger and various other parts and spring pinned in place during assembly. You never have to take this apart, so don’t. If your Thunder Ranch 590 gets so grubby the trigger assembly needs cleaning, press the cross pin out, and dump the assembly in your ultrasonic cleaner. Lube once it is clean and dry, and you’re done.

Loading port of 590 shotgun — The loading port of the 590 is not blocked by a lifter. In fact, no Mossberg 500 or derivative, since 1961, has a lifter blocking the loading port. ( Photo Provided by Author)

While we’re at it, let’s go over disassembly. Make sure your 590 is unloaded. As mentioned, push the cross pin out. It is the rear pin, what looks like a pin forward of it is the pivot boss of the lifter. Leave it alone for now. Then lever (it is hooked in place at the front) the trigger assembly out. The shell stop will fall out when you do this. Unscrew the cap on the end of the magazine tube. Pull the forearm back slightly, to unlock the action. Now you can slide the barrel off of the tube. Press the forearm back far enough that the bolt plate lines up with the clearance cuts and lift the plate out. Slide the forearm forward, and then fish the bolt out of the receiver. To remove the lifter, reach in and pinch the two bars of it towards each other, and once the bosses clear the receiver holes, lift it out. The disassembly sounds more involved than it is, and once you get the hang of it, it will be easy. You are done except for the scrubbing. Which, shotguns being shotguns, will involve a lot of scrubbing.

Rear tang style safety and red dot optic mount plate on shotgun — The safety is that big button sculpted to fit your thumb, with the red dot that shows the 590 is ready to go. Ahead of it is the red-dot optic plate, and ahead of that the first set of scope mount holes in the receiver. ( Photo Provided by Author)

940 Pro

Ejection port view of 940 shotgun with large charging handle — The Thunder Ranch 940 Pro, showing the logo, the charging handle, bolt release and the two trigger housing pins. (Photo Provided by Author)

The Thunder Ranch 940 Pro is built on the 940 Pro action, the competition model that Jerry Miculek had a big hand in testing and developing. Knowing Jerry, the testing was probably breaking one engineering prototype after another by shooting it until it failed, ending when he just couldn’t break anything. Then they made it soft to shoot, and able to handle regular or three-inch magnum shells. Trust me, if jerry can’t break it, you can’t. At least not by using it properly. As with so many things, hammer marks and tire tracks have a way of voiding warranties.

The Thunder Ranch 940 Pro has a large bolt release lever on the right side, along with a large charging handle. Inside, the 940 action has a piston in a cupped loop underneath the barrel. To make cleaning easier the piston has a nickel boron coating. (The 940 Pro is good for 1,500 rounds between cleaning, or so Mossberg says. Me, I’m a bit more OCD on shotgun cleaning than that.) That piston acts against a lightweight spacer, and the spacer slaps the dual-rod connector. That’s how Mossberg designed the action to handle light and heavy loads. Instead of the gas flow driving a piston that works the action, the various parts of the piston-spacer-dual rod connector each delivers and moderates the force on the action. The dual rods of the connector means that the bolt plate, the part that locks, unlocks and shuttles the bolt back and forth, has even force applied to its movement. None of this getting shoved from just one side, and potential binding nonsense here.

Knurled charging handle on 940 — The charging handle is big so you can easily reach it, past the large bolt release button. (Photo Provided by Author)

The 940 Pro, like the 940, has a magazine tube open on the end, and the magazine cap both contains the magazine spring and follower, and locks the barrel in place. Here, Mossberg has added a magazine extension, bringing the capacity up to seven 2-3/4-inch shells in the magazine. And this still with a barrel that is eighteen and a half inches long. While you are loading the Thunder Ranch 940 Pro, you might notice that you are enjoying the experience. That’s because the opening of the loading port has been enlarged and dehorned, and there’s an anodized, bright orange/red follower that drives the shells, so you can clearly see if the one you are shoving in is the only one there or not.

The handguard of the Thunder Ranch 940 Pro, and the bracket ahead of it, are noteworthy. First, the handguard is trim and well-shaped to let you both maintain control and to not be a bulky hindrance to use. Plus, it has a pair of quick-detach (QD) sling swivel sockets, one on each side, up at the front. Some people favor slings for shotguns, others don’t. Those who do favor them have an easy way to attach a sling. Those who don’t will find the QD sockets are not in the way. You might not even notice them at all, after a while. In front of that is a synthetic bracket that clamps to the barrel and magazine tube. This serves a bunch of purposes.

Barrel band on the 940 with Mlok slot for mounting ligh rails — The bracket on the front of the 940 Pro supports the magazine tube and provides an extra Mlok mounting slot on each side. (Photo Provided by Author)

First, it gives the magazine tube support during recoil. When you shoot, the recoil causes the magazine tube to flex up and down. The bracket supports it. It also gives the magazine tube extension support and protection in the rough handling that use, training and defense applications might subject it to. If it so happens that you need to be using your Thunder Ranch 940 Pro as an impact tool, the magazine tube has some protection against being bent. The bracket also has M-LOK slots, in case you want to use something other than a sling, or gear that won’t work with the QWD sockets.

Forend of 940 with QD sling mount — The handguard has QD sling sockets, one on each side, out at the front end. (Photo Provided by Author)

The stock on the 940 Pro is adjustable for length of pull, pitch, cast and for all I know the phase of the moon. The bag containing the various parts to adjust it was enough gear to work as a doorstop. Me, I typically run firearms just as they come out of the box and didn’t try any of the adjustments. But if you are not built like me (think Gary Cooper) the adjustments could make the already good Thunder Ranch 940 Pro even better.

Disassembly and cleaning? It takes more steps than the 590 does, more steps than I have time here, but it is easy if messy (shotguns are like that), and clearly explained in the owner’s manual. One detail that I like is that it is easy to unload the magazine tube before cleaning, if that’s how you are starting. Again, in the manual, risk the points deduction on your man-card and read it.

Loading port view of 940 — The 940 Pro loading port has been enlarged, beveled, and here shows the red-anodized follower for easy loading.(Photo Provided by Author)

Thunder Ranch Series

The additions of the Thunder Ranch Series are details like the QD sling swivels, and the thunder Ranch logo and name engraved on the receiver. The two shotguns also get a Cerakote exterior, in Patriot Brown, and a fiber optic front bead. There are a host of features that they share with the regular Mossberg shotguns but are even more appreciated on the Thunder Ranch Series.

From day one, the Mossberg 500 had the safety lever on the top rear center of the aluminum receiver. This made it ambidextrous in an era when all shotguns used push-button safeties set up for right-handed shooters. On the Thunder Ranch Series, the safety button is not just a ridged bar, but it is a checkered tab with curved sockets built-in to fit the tip of your thumb. You would be hard-pressed to miss this, even in the stressful environment of defense.

The Thunder Ranch Series also has the Mossberg optics-ready cut on the receiver. Unbolt the cover plate and you can attach an RMSc-compatible red-dot optic. As an old-school shooter, I’m still getting used to the idea, but a lot of new shooters see it as a must-have, and Mossberg (and Clint Smith) have you covered here. As if that wasn’t enough, the receiver is drilled and tapped on top for a scope base. So, if you decide that for hunting season you want to convert either of your Thunder Ranch shotguns to a deer-hunting tool, there you go.

While the 940 Pro has an adjustable stock, the 590 does not. Instead, it has a durable set of synthetic stock and forearm, simple, sturdy and handy. The length of pull on the 590 is listed as “short” but for most shooters, a twelve-inch pull isn’t particularly short. In fact, it’s just about right. The 940 Pro is a lot harder on your wallet than the 590 might be, not that either are particularly pricey. In this modern era of Bidenbucks (hopefully changed by the time you read this), just over six bills for a fully featured Mossberg 590 is not out of line, and just over twelve for a self-loader isn’t bad either.

One detail that neither have are choke tubes. In this modern time of every shotgun has screw-in chokes, you’d think that is a hindrance. Well, no. Back in the old days, buckshot was, well, erratic. You could not count on just any load delivering the performance you wanted. You had to (and we did) test every brand and load until you found the one (or if you were lucky, two or three) that delivered the pattern you wanted. When you found it, you stocked up. Why? Because there was no guarantee that the next time you needed it, the manufacturer hadn’t changed some minor (to them) detail, a detail that changed your pattern and made you start all over again. Today? The pattern-control wads on buckshot (and other pellet sizes as well) means they all deliver good-to-excellent patterns. Patterns that can be too tight for some of us old farts. So, in the interests of keeping things simple, and durable, Clint specified a cylinder choke on the barrels. So, fewer parts to keep track of, nothing to work loose, and less expense than machining for choke tubes.

Testing

Well, the testing was simple. I broke out a case of skeet loads and proceeded to spend a pleasant afternoon hammering falling plates and pepper poppers. At no time did either the 590 or the 940 Pro give me any problems. As I mentioned, I’ve been using one or another 500/590 since the early years of the Reagan Administration. The pump action holds no surprises, but I still find it a marvelous tool. My crusty old 500 I had in Flint was a single-bar model made for the long-defunct Montgomery Wards store. It came well-used, and I shot it enough that Mossberg was eventually not able to repair it (that’s a lot of ammo, by anyone’s standard) and you will likely never get to that point. It never had a functional problem, despite only having one action bar, but the dual-bar design of the Thunder Ranch 590 is even smoother. The one drawback you might find is one of the advantages of the basic 500 design: the light weight. With an aluminum receiver and a short barrel, the empty 590 tips the scales at just over six and a half pounds. I can assure you that if you use anything more than low-recoil buckshot loads, you are going to feel it. A lot.

Target showing pattern spead with 00 buck shot — Wads leave a mark. Or even more. Here is a typical tight pattern from Hornady 00 buck, at ten yards. The big hole on the right is the wad. (Photo Provided by Author)

The Thunder Ranch 940 Pro, at mid-seven pounds, is easier to shoot, both because of the extra weight, and the gas system spreading the jolt of felt recoil out over more time. I’ve shot the 940 JM Pro Competition model up at The Pin Shoot for a day’s worth of factory buckshot, and the experience is not abusive. So, practicing with your Thunder Ranch 940 Pro using the buckshot you expect to use (and testing it for patterns) will not be a shoulder-breaking experience. A wallet-breaking one, perhaps, but not your shoulder.

Accuracy Data from various ammunition — (Data Provided by Author)

In testing, I found, as expected, that the modern pellet-control wads do their job. All the loads tested delivered tight groups at ten yards, but there is one detail you’ll have to be aware of: the wads. Since the wads do their job and keep the pellets together, the wads tend to be close to the pellet trajectory in the close distances you’ll use them. It was not unusual to see a heavy dent, and even holes, in the cardboard of targets, caused by the wads. Yes, a wad weighs less than what a buckshot pellet does, but it is still leaving the muzzle at the same velocity. Depending on the load, at 1,200 to 1,600 fps, and it is going to leave a mark.

Target showing pattern of the 940 shotgun — At ten yards, this Federal load shot a very nice pattern. In the middle of the buckshot hits is the dent left by the wad. (Photo Provided by Author)

Now, should you spring for the Thunder Ranch Series? Hmmm. The lowest-cost comparable 590 is a hundred dollars less. You give up the Cerakote finish, the fiber optic bead, the larger safety button, and the Thunder Ranch logo. I think the safety, finish, and bead are worth more than the $100 saved, and the cool factor of the logo, is a bonus. As far as the 940 is concerned, you can jump up to the 940 Pro Tactical if you simply must have a screw-in choke system, but it will cost you a few dollars more. The only other 940 Pro Tactical you can look at is the five-shot, which saves you, again, $100, but you’ll have to score your own extended magazine tube to bring it up past five shots. Nope, they are both smoking deals, and can’t be duplicated at a lower price point, which pretty much describes the entire Mossberg line: smoking deals, and can’t be beat on price. That’s why I have a rack of them.