The Mossberg 590 is the fighting version of America’s other pump gun: higher capacity than a field 500, a magazine tube you can open at the muzzle end, a metal safety and trigger guard on most models, and in 590A1 form a heavy-walled barrel. It arrives closer to ready than almost any other pump shotgun, so a 590 build is about filling the handful of gaps rather than fixing the gun.
One thing to settle before you spend anything. The 590 shares a great deal with the Mossberg 500, and that’s mostly good news, but Mossberg themselves put one exception in writing and it’s the expensive one. We went and read their manual.
Table of Contents
How we tested: Every pick here is ranked against our testing methodology. Minimum round counts, accuracy and reliability protocols, the failures that disqualify a gun.
Mossberg 590 Upgrades at a Glance
| Category | Our Pick | Fits | Why It Makes the List |
|---|---|---|---|
| Magazine extension | Mossberg or Lancer tube | 590, match to barrel | More shells on a fighting gun |
| Stock | Magpul SGA | 500/590/590A1 | Adjustable pull, proper cheek weld |
| Forend | Magpul MOE M-LOK | 590/590A1 | Grip and a place for a light |
| Sights | Ghost ring kit | 500/590 | Real precision over a bare bead |
| Weapon light | Streamlight TL-Racker | 500/590 | Light and forend in one part |
| Shell carrier | Mesa Tactical SureShell | 500/590 | Spare shells on the receiver |
| Optic mount | Picatinny receiver rail | 500/590 | Both-eyes-open aiming |
| Sling | Magpul MS1 two-point | Any gun with mounts | Hands-free carry and retention |
| Sling mount | Mag cap QD swivel | 590 and 835 tubes | The part the sling needs first |
| Heat shield | Mossberg factory kit | 500/590 12 gauge | Grab the barrel after a string |
What Actually Fits a 590
mossberg.com returns an HTTP 403 to us and has done from every address we tried, but Mossberg’s own owner’s manual covering the 500, 505, 510, 535, 590 and 835 is mirrored publicly. We read all 92,664 characters of it. One sentence is worth the whole document:
The 500, 505, 510, 535, 590 and 835 barrels are interchangeable only with barrels of the same model, gauge and capacity.
Mossberg owner manual, 500/505/510/535/590/835
A note on that source, because you should be able to judge it. The edition we could obtain with readable text is the Spanish-language printing of Mossberg’s own manual. It’s their document rather than a third party’s, but it’s a translation of their English text, and the English item available to us is a shorter manual that doesn’t carry this passage. The same page adds that right-hand and left-hand model barrels do not interchange either.
Why the barrels don’t cross
The manual answers that too, in the takedown instructions. For the 590 and 835 it says to unscrew the magazine tube cap, turning it counterclockwise, and draw the barrel off. Mossberg’s separate military manual documents the other arrangement in the same family: the 500M MILS unscrews a magazine cap, while the 500 MILS comes apart with a take down screw instead.
Two different ways of holding a barrel onto a receiver, inside one product line. That’s the mechanism behind the rule, and it’s why a barrel is the one part on this platform where “it is a Mossberg, it will fit” gets expensive. Magazine extensions live on the same tube and follow the same logic: match the part to your model, and match the tube length to your barrel so it does not overhang the muzzle.
What genuinely does cross over
Most of this page, which is the good news. Stocks, forends, sights, optic rails, lights and shell carriers are listed for the 500 and 590 together throughout the prices below, and that’s real rather than lazy cataloging: the Magpul SGA is sold as fitting the 500, 590 and 590A1 in one listing, and the Magpul MOE forend names the 590 and 590A1 together. The receiver and the stock interface are shared. The barrel and the tube aren’t.
The specification on the cover
While we had Mossberg’s military manual open, its cover is worth quoting because the phrase gets repeated online without a source. It reads: “SHOTGUN, 12-GA. RIOT TYPE II, CLASS I PER MIL-S-3443E”. So the military specification behind these guns is real, it has a number, and Mossberg print it on their own documentation.
We are going to stop short of the claim you’ll see everywhere, though, including in an older version of this page: that the 590A1 is simply “the shotgun the military issues”. The manual we found is for the 500 MILS rather than the 590A1, and a specification is a standard to build to rather than a record of what was bought. The spec citation is checkable. The procurement story isn’t, from anything we could read.
Which 590 Do You Actually Have?
“590” covers a wider spread of guns than the name suggests, and the retailer listings for these parts make that obvious: a single search returns the 590, 590A1, 590M, Shockwave, Retrograde, Cruiser, Thunder Ranch and Tactical, at prices from thirty dollars to over five hundred. Four questions sort out what you own and what it takes.
Tube-fed or magazine-fed
The 590M feeds from a detachable box magazine rather than a tube under the barrel. That’s a different gun for parts purposes and the difference is not subtle: every magazine extension on this page is irrelevant to it, because there’s no tube to extend, and the magazine cap sling mount has no cap to replace. If your receiver has a box hanging below it, buy 590M parts and nothing else.
590 or 590A1
The A1 is the heavier-built version: a thick-walled barrel, a metal trigger guard and safety button where the standard gun may use polymer. For this page it changes very little. The Magpul MOE forend is listed for the 590 and 590A1 in the same product, the SGA stock covers the 500, 590 and 590A1, and sights, rails and shell carriers are shared. The barrel is where they part company, which is the rule from the section above.
Barrel length, and the thing it decides
Barrels come at 18.5 and 20 inches most commonly, and this decides your magazine extension more than anything else. An extension longer than your barrel overhangs the muzzle, which is ugly, unbalanced and in some configurations unusable. Measure before you order, and if the listing gives a shell count rather than a length, work out which barrel that count assumes.
Shotgun or “firearm”
The 590 Shockwave, with its bird’s head grip and short barrel, isn’t legally a shotgun in the United States. It’s classified separately because it was never built with a shoulder stock, and that classification is exactly what a stock would destroy. Everything on this page that touches the rear of the receiver is therefore off the table for a Shockwave, whatever a product listing implies, and fitting a stock to one is a federal matter rather than a fitment question. Forends, lights, sights and shell carriers are fine.
We are not lawyers and this is not legal advice; it’s a warning that the most consequential part on this page for a Shockwave owner is the one we would tell you not to buy. Check your own state and federal position before you change anything structural on a short-barreled gun.
Best Magazine Extension: Tube, Not Clamp
More shells is the single most valuable change you can make to a fighting shotgun, and the 590’s tube design makes it straightforward: there’s no cleanout cap to work around, which is exactly the difference between this gun and a 500. Mossberg’s own extension and Lancer’s carbon fiber LSX tubes are both in the prices below.
The heading is deliberate. An earlier version of this page priced a “magazine extension” and the listings it returned were an extension tube end cap, a barrel clamp, a magazine extension support clamp, and an MXT package for a Beretta 1301. Those are all real products and none of them is an extension. A clamp braces the extension to the barrel and is worth owning second; it’s not the thing that holds shells. The listing below is filtered to tubes.
Best Stock: Magpul SGA
The SGA gives you length of pull you can adjust with spacers, a comb high enough to get behind a red dot properly, and sling points at both ends. On a shotgun, fit is not a comfort question: a stock that is too long stops you mounting the gun cleanly under pressure, and a comb that is too low means you never see your sights the same way twice.
It’s listed for the 500, 590 and 590A1 in one product, which is the kind of listing the section above is about. One shopping warning: complete Mossberg shotguns that ship with an SGA fitted turn up in the same search, at seven hundred dollars rather than a hundred. Their titles read “Shotgun with Magpul SGA Stock”, so read the first three words of any result before you look at the price.
Best Forend: Magpul MOE M-LOK
The factory forend works and gives you nothing to hold onto when your hands are wet or gloved. The MOE M-LOK version adds real texture and M-LOK slots along both sides, so a light or a sling point goes on without a clamp hanging off the magazine tube.
Worth deciding before you buy: if a light is the plan, the TL-Racker further down replaces the forend with a light built into it, and you don’t want both. The MOE is the right answer if you want a better grip, a sling point, or the freedom to choose your own light later.
Best Sights: Ghost Ring Kit
A bead is fine for a pattern at short range and hopeless for a slug at fifty yards. A ghost ring rear with a protected front post gives you an aiming system rather than a suggestion, and it’s the upgrade that turns a defensive shotgun into something you can also shoot slugs accurately with.
Mossberg’s own kit and the XS Shotrail are both listed for the 500 and 590, and XS offer tritium versions if the gun has a night job. As with the stock, complete shotguns fitted with ghost rings appear in these results at four hundred dollars. We filter them out below; a retailer’s own search will not.
Best Weapon Light: Streamlight TL-Racker
A home-defense shotgun needs a light, because identifying what you’re pointing at isn’t optional, and a shotgun makes that awkward: the forend moves. The TL-Racker solves it by being the forend, with 1,000 lumens and a switch under the hand that is already there. Nothing to snag, nothing clamped to the tube, and the light goes where the gun points.
It’s the cleanest light solution on a pump gun and it’s listed for the 500 and 590 together. Remember it replaces the forend, so this and the Magpul MOE above are alternatives rather than companions. Check the length against your magazine tube and extension before ordering.
Best Shell Carrier: Mesa Tactical SureShell
A shotgun runs dry fast and reloads one shell at a time, so spare rounds on the gun are worth more here than on any other weapon. Mesa Tactical’s SureShell carriers bolt to the receiver, hold six shells where your support hand can reach them, and are rigid enough that the shells stay put under recoil, which the elastic ones aren’t always.
Several versions include an integral Picatinny rail on top, which means this pick and the optic mount below can be the same purchase. Decide that first. Buy the carrier cut for your receiver, and practice the reload, because a side saddle you cannot work without looking is decoration.
Best Optic Mount: Picatinny Receiver Rail
A red dot on a shotgun is a bigger gain than people expect, because it lets you shoot with both eyes open and puts the aiming point where the pattern is going regardless of how your head is on the stock. The 590’s receiver is drilled for a rail, so this is a bolt-on job rather than a gunsmithing one.
Prices run from ten dollars for a basic NcSTAR rail to forty for a machined one, and on a shotgun the difference matters more than on a rifle, because a pump gun beats an optic mount harder than most people credit. Buy a dot rated for shotgun recoil, and pair the rail with the SGA stock above so your cheek lands where the dot is.
Best Sling: Magpul MS1
A loaded 590 is heavy and a shotgun you’re carrying is a shotgun you aren’t doing anything else with. A two-point sling gives you both hands back and keeps the gun on you, and the MS1 is the default for good reason: a quick adjuster you can reach without looking, and nylon that doesn’t stretch when it gets wet.
Set the length so the gun sits across your front with the muzzle down and the stock reachable. A sling that is too long is worse than none, because it lets the gun swing into everything you walk past.
Buy This With the Sling: Mount Hardware
Here is the gap the old version of this page left open. It recommended a sling and never mentioned that a 590 may have nowhere to attach one. Factory sling swivel studs are not universal across the line, and if yours has none, the sling arrives and sits in a drawer.
Two solutions are priced below. A magazine cap swivel from GrovTec or Uncle Mike’s replaces the cap at the muzzle end with one that carries a QD socket, which is the tidiest answer on a tube gun. At the other end, Magpul’s SGA receiver sling mount gives you a rear attachment point, and it’s the obvious companion if you fitted the SGA stock further up this page. Check what your gun already has before ordering either.
Best Overlooked Part: Barrel Heat Shield
This one looks like costume and isn’t. Shotgun barrels get hot quickly, and a short defensive gun puts your support hand close to a barrel that has just had shells through it. A heat shield gives you somewhere safe to grab in a hurry and stops a hot barrel touching anything it should not.
Mossberg sell the factory kit for the 500 and 590 and it’s a bolt-on. It’s also the part most likely to be the reason people think the 590 looks the way it does, which is fine: a thing can be useful and still look good. Check the length against your barrel, and note that complete Retrograde models ship with one fitted, so those turn up in the search at five hundred dollars.
What a 590 Parts Search Actually Returns
Every price block here runs against live retailer listings, so we see the results before you do. On a shotgun one problem dominates, and it’s worth naming because it wrecks your sense of what things cost.
Whole shotguns, priced as parts
A gun that ships with an accessory names that accessory in its title, so it outranks the accessory. Building this page we filtered out a 703 dollar Mossberg 590M listed as “Shotgun with Magpul SGA Stock” from the stock results, a 440 dollar M590A1 “Shotgun with XS Ghost Ring Sights” from the sight results, and Retrograde models at 485 and 520 dollars from the heat shield results, because those ship with one fitted.
The pattern is easy to spot once you know it. If the title reads “Shotgun with” anything, or carries a capacity like 6+1, it’s a gun. We also went looking for a replacement barrel to price for you and gave up: every result was a complete shotgun between 434 and 520 dollars whose title happened to contain the word barrel. There’s no barrel card on this page for that reason.
The rest of what we filtered
- A Beretta 1301 package. The magazine extension search returned a Nordic MXT extension package for a Beretta semi-auto. Right maker of part, wrong shotgun entirely.
- An AK receiver cover. The optic rail search offered an NcSTAR Picatinny mount for an AK. Same maker, same category, different weapon.
- A 20-gauge shell carrier. Searching stock-mounted carriers returned a Monstrum unit in 20 gauge. Wrong gauge is the version of wrong gun that is hardest to catch, because everything else about the listing looks right.
- A screw instead of a part. A search for an oversized safety button headlined a 4.99 dollar “Safety Button Screw”. The screw that holds the button isn’t the button.
- A pistol magazine spring. A magazine spring search returned a Wolff spring for a Springfield XD in .45 ACP, which is a handgun.
One thing that is not a trap, since the opposite mistake costs you too: listings naming the 500 and 590 together are almost always genuine shared parts, and so are ones naming the 590 and 590A1. Your gun named among several is fine. Only another gun named, or a four-figure price, means walk away.
How to Prioritize Your Mossberg 590 Build
The 590 starts closer to finished than most pumps, so this is a short list. In order:
- A light. Target identification is the one thing even a tactical shotgun doesn’t come with.
- Sights, if yours wears a bare bead. Ghost rings, or a rail and a dot.
- Stock and forend for fit, unless the TL-Racker already took the forend slot.
- A sling and the hardware to hang it on, bought together.
- A magazine extension, matched to your barrel length and to your model.
- A shell carrier and a heat shield to finish it.
Want the background on the gun first? Read our Mossberg 590A1 review and the Mossberg 500 vs 590 comparison, then see the platform in our best pump-action shotguns and best home-defense shotgun guides. Building the 500 instead? See our Mossberg 500 parts guide.
Frequently Asked Questions
Do Mossberg 500 and 590 parts interchange?
Most of them do, and one important one does not. Stocks, forends, sights, optic rails, lights and shell carriers are sold for the 500 and 590 together, and that is genuine rather than lazy cataloging. Barrels are the exception, and Mossberg say so themselves: their owner manual states that 500, 505, 510, 535, 590 and 835 barrels are interchangeable only with barrels of the same model, gauge and capacity, and adds that right-hand and left-hand model barrels do not cross either. Magazine extensions follow the same logic, because they live on the same tube.
Why do Mossberg barrels not interchange between models?
Because the models do not all hold the barrel on the same way. Mossberg own manual tells 590 and 835 owners to unscrew the magazine tube cap and draw the barrel off, while their military manual documents a different arrangement in the same family: the 500M MILS uses a magazine cap and the 500 MILS comes apart with a take down screw. Two retention systems inside one product line is the whole reason a barrel is the part where assuming it will fit gets expensive.
What is the best upgrade for a Mossberg 590?
A weapon light, because target identification is the one capability even a tactical shotgun does not ship with, and on a pump gun a forend light like the Streamlight TL-Racker is the tidiest way to get one. After that, sights if yours wears a bare bead, then a stock and forend for fit. The 590 already comes with high capacity and a metal safety on most models, so you are refining rather than fixing.
How many rounds does a Mossberg 590 hold?
It depends on barrel length and magazine tube, and the common factory configurations run from six plus one to eight plus one of 12 gauge, which is more than most field pumps. A magazine extension pushes that further. Match the extension length to your barrel so the tube does not overhang the muzzle, and match it to your model, because the tube is part of the barrel retention system rather than a separate accessory.
Do Mossberg 590 and 590A1 parts interchange?
Largely yes. The A1 is the heavier-built version with a thick-walled barrel and metal trigger guard and safety button, and it shares stocks, forends, sights, lights, shell carriers and optic rails with the standard 590. The Magpul MOE forend is listed for the 590 and 590A1 in one product and the SGA stock covers the 500, 590 and 590A1. The barrel is where they part company.
Is the 590A1 the shotgun the US military issues?
We are not going to tell you that, because we could not source it. What is checkable is that Mossberg print a military specification on their own documentation: the cover of their MILS manual reads "SHOTGUN, 12-GA. RIOT TYPE II, CLASS I PER MIL-S-3443E". That specification is real and it has a number. But the manual we could obtain covers the 500 MILS rather than the 590A1, and a specification is a standard to build to rather than a record of what was bought.
Can you put a red dot on a Mossberg 590?
Yes, and it is a bigger gain than people expect, because it lets you shoot with both eyes open and puts the aiming point where the pattern goes regardless of how your head sits on the stock. A Picatinny receiver rail bolts on, and several Mesa Tactical shell carriers include an integral rail so the two can be one purchase. Buy a dot rated for shotgun recoil, because a pump gun is harder on an optic than most rifles are.
Why does a shotgun accessory search show four-figure prices?
Because a gun that ships with an accessory names that accessory in its title, so it outranks the accessory. Searching for a Magpul SGA stock returns a complete 590M listed as "Shotgun with Magpul SGA Stock" at over seven hundred dollars; searching for ghost ring sights returns an M590A1 "Shotgun with XS Ghost Ring Sights". The tell is in the title: if it reads "Shotgun with" anything, or carries a capacity like 6+1, it is a firearm and not a part.
3,976+ Gun & Ammo Deals
Updated daily from 200+ top retailers. Filter by category, caliber, action type, and price.
Related Guides