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ACM Mossberg 500 Shotgun

ACM M500 Shotgun

Wanting to just kick the door and blast you way into the room in CQC skirmishes, having a shotgun would come in handy. Though airsoft shotguns don't shoot out the same number of pellets as the real ones, still they are a handy tool to play with. You can act as the “breacher” playing SWAT scenarios.

The Mossberg 500 is a shotgun manufactured by O.F. Mossberg & Sons. Rather than a single model, the 500 is really a series of widely varying hammerless, pump action repeaters, all of which share the same basic receiver and action, but differ in bore size, barrel length, choke options, as well as stock and forearm materials.

All modern 500s are based on the same basic design, using dual action bars, which are less likely to bind than a single action bar design, and a single large locking lug to secure the breech. The magazine tube is located below the barrel, and is screwed into the receiver. The slide release is located to the left rear of the trigger guard, and the safety is located on the upper rear of the receiver (often called a "tang safety"). Sights vary from model to model, from simple bead sight to a receiver mounted ghost ring or an integrated base for a telescopic sight. Most models come with the receiver drilled and tapped for the installation of a rear sight or a scope base. The factory scope base is attached to the barrel via a cantilever-type mount, which places the scope over the receiver but keeps it with the barrel if the barrel is removed.

Intended for use in harsh and dirty conditions, such as waterfowl hunting or combat, the Model 500 series is designed to be easy to clean and maintain. All Model 500s feature interchangeable barrels which may be removed without the use of tools, by loosening a screw on the end of the fore end, which allows the barrel to be removed. The bolt locks into a locking lug located on the top of the barrel, ensuring a solid bolt-to-barrel connection and not relying on the receiver for any locking strength. The trigger guard can be removed by pushing out one retaining pin, and pulling downwards. The elevator can be removed by squeezing the sides together, freeing the pivot pins from the receiver. The fore end can then be moved to the rear, allowing the bolt and bolt carrier to drop out, and then the fore end can be removed by moving it forward. The cartridge stop and interrupter will then fall free, leaving just the ejector and the safety in the receiver, held in by screws. The magazine spring and follower may be removed by unscrewing the tube from the receiver. This level of field stripping is sufficient to allow all components to be cleaned.

- From Wikipedia

The ACM M500 SSB

This Gas shotgun is an exact copy or clone, if you would prefer to call it, of the Marushin M500 Mossberg Shotgun. The Mossberg 500 is actually called M500 Persuader Shotgun according to Mossberg & Sons.


The shotgun comes in the usual cardboard lid Styrofoam box. Information printed on the box tells you the shotgun variant, in this case the M500 SSB and the size of BB to use as this type comes in both 8mm and 6mm bbs. What is interesting in the packaging is that there is no mention of the manufacturer thus it has been dubbed as an ACM (All-China-Made) airsoft shotgun.

Upon opening the box, you will be greeted by the shotgun, this one is the black version used by law-enforcers. Also included is a manual with take down guide, spare rubber O-rings, pair of allen screw drivers, a pack of BBs and a cleaning rod.

First Impressions and General Appearance

First impressions is always important on anything that we buy and this is the same with purchasing airsoft products. Most players not only go for reliability but also for looks. In this hobby of acting out our fantasies of being soldiers or law enforcers, it is important that we get the right look or at least as close to it as possible.

The ACM M500SSB Shotgun is indeed an impressive piece of kit considering that it is a budget airsoft shotgun. If you pick this shotgun to use, the first thing that you will notice is the weight. It is heavy thanks to all the metal parts that it has. I did not weigh it but it should weigh more that 5lbs. easily. The shotgun is 37.7 inches long from the end of the stock to the tip of the barrel which I was told is almost the same weight and length as the real thing. As with most ACMs there are no markings of any kind on this shotgun.

This particular ACM M500 is the black version which is the version used by the police and other law enforcement agencies. The finish is very good, probably one of the best finish that I have seen on an ACM. Its matte black so there is no shine on the main body making this good for indoor CQC battles where darkness is your friend. Another impressive thing that I noticed is that the paint is durable and does not scratch easily although the usual paint imperfections that you see on other ACMs are also there.

The shotgun is full metal. Actually the only non-metal external parts of this shotgun are the cocking handle, the stock, the front sight and the rear sight.

Nothing special with the outer barrel and the front sight is fixed. When you look through the barrel, you will see the inner barrel nicely held around 1.5 to 2 inches from the end for outer barrel and unlike some high end shotguns, this shotgun only is a single-barrel type.

The magazine tube that is located underneath the main outer barrel holds the fore-end or the action pump and the action bar. The fore-end is a bit flimsy and wobbles a lot. It also has the tendency to slide down when the shotgun is carried on a vertical position. The action bar which actually "cocks" the shotgun is metal but looks weak. There have been reports of this bar breaking on the high end version so it is not advised to pump the shotgun with one hand, no matter how cool it looks. The sound that the shotgun makes when pumped is actually good and does sound like a real shotgun being cocked.

The receiver is full metal. The shell ejection port has an aluminium slide which slides back each time you pump the shotgun. On top of the receiver is the rear sight with its height adjustable by turning a dial at the bottom of the precision sight. The safety button is located at the top rear end of the receiver and can easily be operated using with the thumb.  The shotgun is in “safe” when this is on the down position.

The shell loading port on the bottom of the receiver is non-functional as this shotgun does not use shells to hold the bbs but the gas valve is nicely hidden in here. The only concern I have is that the gas valve is not covered or protected from dirt. Just behind the loading port is the trigger guard which, obviously, houses the trigger. The trigger is firm and needs a good determined pull in order to fire the shotgun. Another nice feature which can also be found on the real thing is an indicator which tells you that the shotgun has been cocked and loaded. This is located on the left side of the receiver just behind the trigger guard. It's a small silver plate that pops out when the shotgun is loaded and one thing that is not encouraged is pumping a loaded shotgun.

Finally the stock. The stock is solidly built. The material I suppose is plastic but is rubber-coated that makes it non-slip. The butt plate is rubber which makes shouldering the shotgun comfortable. The shotgun both have front and rear sling caps, but for some reason, there are no sling swivels included.


Loading the bbs in this shotgun is not the quickest thing that can be done, and I think it is not a viable thing to do in the field during a game as it could take some time.

The bbs still go in the magazine tube but since this shotgun does not use magazine shells, they will have to be manually loaded.

First, you will need to access a latch that locks the magazine tube in place. This is located at the front-end of the magazine tube on the right side. To unlock it, you simply press then turn it 180 degrees from left to right. Then pull the pump half way down as this will reveal a small access at the bottom of the magazine tube. Pull the end of the barrel to reveal the magazine tube. Continue pulling until you can't pull  anymore and the end of the magazine can be seen by the access hole. Then simply fill the access with bbs. Each magazine can hold 50 bbs with some room to spare and there are three tubes, so that makes it a good 150 rounds to fire. I would not advise overfeeding the tubes as it makes it difficult to push them back into place.  Just rotate them when one is full and fill the next one and so on. Once all are filled just push the magazine tube back and lock into place.

Ready to fire? Not quite yet. Remember this is a gas gun so don't forget to load the gas. Because the shotgun only has one barrel and fires 5 bbs per shot, you will need at least green gas to avoid bbs dropping on your feet. It needs quite a lot of gas to fill it and if done properly, you should be able to empty all three tubes with one gas load.

Firing and Performance

Now that you have loaded your ammo, it's time for the fun part. Pumping or cocking the shotgun is easy. It's actually nothing compared to spring shotguns. Just make sure that you pull the pump enough for the loaded indicator to pop out, otherwise the shotgun is not cocked.

Firing the gun is very cool, 5 bbs are fired each time and they start flying out the barrel clusters together then like jet fighters in formation, spreading out to at least 6 to 12 inches apart once they reach 15 feet. Range is good for an airsoft shotgun with accurate hits from around 25 to 30 feet.

Muzzle velocity is difficult to measure and inaccurate due to 5 bbs going through the chrono. Readings are between 250 fps lowest to 281 fps highest.

I was not happy with these readings so I decided to do the "Poor Man's Chrono" and results are impressive. Using green gas at around 12 degrees Celsius. First blast went through both sides of the can (350 to 370 fps). Second blast through the bottom central (420 to 450 fps). Third blast through center on top of the can, (520 to 540 fps). There are some factors that I think will need to be considered with these results and one is the weight of the projectiles as 5 bbs hit the can at the same time so it's not actually a single 0.2 bb hitting the target. But still I think it's impressive.



  • 1:1 replica of real world counterpart
  • Good attention to details
  • Solid built overall
  • Good finish
  • Impressive performance especially spread effect of shots.


  • Slow and fiddly loading procedure
  • Pump is a bit flimsy and wobbles
  • Very limited with regards to what you can add on it.

Overall, this is an impressive gas shotgun considering it's an ACM. It could be very good in CQB as a room clearing weapon or a secondary field weapon. We could probably expect the same problems that other gas shotguns have but with the price and performance so far... we are very happy.

Not without its imperfections, but if this is where ACMs are headed, then keep them coming!

Special thanks to Greg and Phil of Elite Airsoft Essex for providing us with the review item.

Regarding the forearm wobble

As an avid collector and user of both airsoft and real-steel firearms, I would like to add my two cents to this review. In the review you stated that the forearm wobbles, and listed it as a con. That's fine -- I would view it as a con too. But that's how the REAL Mossberg 500 is. They're known for having wobbly forearms. People have written to Mossberg to tell them their shotguns' forearms are wobbly, but Mossberg has yet to do anything about it, and probably never will. It's just the way they are. So in a way, having the wobbly forend on this ACM shotgun is actually MORE realistic than if it was 100% solid!