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Compact All-purpose Tactical Shotgun (CATS)

By J.M. Ramos

It’s been a number of years since I did a two-part series article on this famous fighting shotgun for SAR magazine. Since then much more sophisticated product enhancements for shotguns became available and the time has come to epitomize the Model M870 one more time. In addition to all these exciting developments, there are also several interesting high capacity bullpup pump action shotguns that have come along in the likes of the Kel-Tec KSG and the Turkish powerhouse UTS-15. These two guns are virtually the same in concept having twin tubular magazines on each side of the barrel and loads in the same manner and packs an awesome 15-shot firepower. Indeed, these distant bullpup twins have very impressive credentials. The question is, are these contenders going to be around for a long time or are they simply a fad of overnight sensation and gone tomorrow? On the contrary, the Model 870 has been around for decades and has been battle proven by the U.S. military and police forces the world over. To date, the M870 still remains as the main bread and butter of its producer – Remington Arms. With the resurgence of military style firearms in the 21st century, many new accessories for this gun have been develop and produced to upgrade its vintage image to the more modern tactical format. Much of the improvements given in particular are attention to furniture style and rail systems. Older models such as the Remington M1100 semi-auto have somewhat milder recoil than its pump action sibling but not good enough to inspire me to shoot more than two dozen rounds continuously without a thick shoulder pad or taking a long pause. The introduction of pistol grip and straight stock configuration for these guns made a difference in recoil management most particularly in muzzle control. There are also bolt-on mounting kits that are tailored to accommodate AR-15 M4 style stocks and pistol grips. These adapters are available in hi-impact polymer or aluminium material. Other manufacturers went further and explored the idea of incorporating a telescoping hydraulic energy built into an M4 style stock extension (Enidine) or a dual spring-loaded recoil reduction system built into the pistol grip (SpecOps). The SpecOps appears to have the most recoil compensating effect dedicated to reducing shotgun recoil. However, this kit lacks the aesthetics and clean lines – something most buyers would go for.

Among these specialty stocks that featured a built-in recoil absorbing system, it was the Fab Defence patented GL-shock absorbing stock that tops them all in both ergonomics and aesthetics. This Israeli made stock featured a premium silicone chrome alloy spring to power its built-in state-of-the-art recoil reduction device. Another unique and patented feature not found on any AR type stock is its built-in anti-rattle mechanism in the form of inward tabs that squeezes both sides of the stock extension’s lower section creating a very snug fit when using a commercial tube. Although the manufacturer claims that the stock will fit both Mil-Spec and commercial tube, the GL will have some looseness with Mil-Spec tubing due to its smaller diameter. Just like most modern M4 style stocks today, the GL also features watertight battery storage and integrated QD sling connectors on both sides. Priced at just under $100, the GL stock is one of the best bargains around with excellent quality and good looks to go along. It comes in a variety of tactical colors and available with optional cheek piece. I have tested the GL stock quite extensively with varieties of 2 3/4 and 3 inch Magnum (00 buck shots and slugs) and the felt recoil is definitely tamed down. It’s like shooting a mild 20 gauge with a 3 inch Magnum and even milder with 2 3/4 inch shell. The usual hard kick of the butt during recoil is replaced by a “push” like feel and it’s not harsh or painful by any means. The recoil absorbing system on this stock really works and will definitely find a good use with any big bore AR or AK. The introduction of these recoil absorbing stocks for use with powerful full bore service rifles and shotgun truly benefited the average consumer without having to go through the services of a gunsmith for expensive barrel porting or installation of a muzzle brake device that may require machining and brazing.

Ideally, to create the ultimate Compact All-purpose Tactical Shotgun (CATS) you must start with a medium size M870 – preferably a police model with a 14 inch barrel and carefully outfit it with the right components. This barrel length puts the overall length of the weapon to the legal 26 inches with the stock folded. My ideal compact all- purpose tactical shotgun must be accurate up to 50 yards with slugs and up to 25-30 yards with 00 buckshot. It should have a minimum 5 plus 1 capacity for defensive application and can accommodate tactical accoutrements such as folding stock (for low profile transport), pistol grips, optic, light or laser, BUIS sight and bipod for those accurate 50 yards shot in certain situations. With all things considered, this tactical package can also be an ideal duty gun for patrol officers who prefer the portability of a folder for ease of carry or transport. In designing the CATS shotgun, the main emphasis is focused on controllability, accuracy, portability, ease of operation, ergonomics, weight and aesthetics. While it does sound like this is going to be quite an undertaking, in reality it is not, simply because most of the ingredients you are going to need is now readily available in the market. It’s just a matter of selecting the right components and putting them together properly.

For recoil management, my top pick of accessory would be the Fab Defence GL and the trend setting Mission First Tactical Battle-Link Minimalist Stock (BMS). The MFT BMS overall design feature is quite impressive. I predict that superlight collapsible stocks (to match the new style slim-line forearms) will be the next wave in tactical stock innovation and MFT’s Minimalist is there first and definitely the one to beat. This stock does not have the usual built-in compartment to accommodate spare batteries or tools to allow trimming as much materials as possible, which helps to keep the weight down to bare minimum. The way I look at it, most pistol grips and forward grips have the internal storage for this purpose anyway so the Minimalist will do just fine without this feature. This stock is made of specially developed reinforced, super tough polyamide from Du-Pont’s military plastic division that is amazingly light at less than 6 ounces. This kept the CATS shotgun weight down considerably when you take into consideration other conventional polymer stocks can easily weigh ten times or more in comparison. Another excellent feature of the Minimalist is the fit to the stock extension. It is very snug with absolutely no rattle or play once installed. The secret is the stock’s assembly hole. This portion of the stock is not round as with conventional stocks; rather it has four corners. If you look closely inside the stock you will see that the assembly hole has a two- step section. The opening of the stock is correct for the diameter of the tubing being used (available for Mil-Spec or commercial). As you push the stock in, the tubing will encounter a resistance once it hits the second step of the hole, which is intentionally made undersize. As you force the stock further into the tubing, the four corners of the hole will flex and tightens against the tubing on all corners resulting in a very snug and rattle free fitting. Once the stock is fully assembled to the stock extension, it slides smoothly from one index to another without the usual rattle or looseness normally associated with other conventional collapsible stocks. What a clever idea. It really works without the need for a fancy lever that may not always do the job. The engineers at MFT really did their homework on this one. To keep the Minimalist ultra light, the overall pattern of the stock is highly skeletonized with the lower half of the butt being extensively trimmed down but leaving the cheek piece section with just the perfect width for maximum comfort when shooting. Another remarkable feature of the stock is the angled section of the butt plate. At first glance, one might think it’s just to make it look more fancy or different from other stocks with flat plates. However, once you shoulder the weapon, you will instantly discover it’s not for decoration. The angled section of the butt acts as a fulcrum that works in natural harmony with the operator from low ready position to instant target acquisition in one precise fluid motion. None of the other competing stocks has this unique feature. The Minimalist stock makes the CATS shotgun lighter, more balance and handles more like a tactical short barrelled .308 rifle than a scattergun. This is one formidable CAT to reckon with.

The installation of a butt stock and pistol grip to the M870 will require an adapter. There are several brands of adapter for this shotgun currently available in the market. They are made of polymer or aluminium materials. Of these adapters, I choose the Command Arms (CAA) RS-870 aluminium pistol grip/stock adapter. This adapter is CNC machined from aircraft grade aluminium and superbly finished and anodized. One thing I like about the CAA adapter is it offers a true straight stock configuration and not with a slight heel drop like others that allows the original factory sight to be utilized. A straight stock arrangement like the AR-15 not only provides better control and recoil management to the weapon but it also assures comfortable aiming posture with tall back-up sights. The CAA adapter will take the AK47 pistol grip and AR-15 butt stock (fixed or collapsible). There are two AK pistol grips that I found perfectly suited for the CATS shotgun: namely the Magpul AK-47 MOE grip and Mission First Tactical Engage AK-47 pistol grip (EPG-47). These two grips differed slightly in configurations with Magpul featuring the more traditional slab-sided styling of a 1911 pistol while the MFT grip utilized the finger-grooved pattern of the Tommy gun. Both grips are very well made and highly ergonomic in nature. The Magpul features an aggressive textured surface on both sides of the grip while the MFT has an added grooved back strap to its textured finger swell for maximum grip purchase. Whatever your choice of grip style, these two brands will fill the bill quite nicely. For butt stock installation, you will need an AR-15 stock extension tube (available in Mil-Spec or commercial sizes). My CATS gun project calls for a folding stock to keep the overall length of the gun to legal minimum overall length in the folded position. With the stock folded, this 14 inch model is the same in overall length as an AR-15 PDW with a 7.5 inch barrel. It’s the perfect harmony between portability and accuracy. Ideally, a compact 10-shot double stack detachable magazine would have put a nice finishing touch to this tactical package but that would require redesigning the gun itself. Speaking of a magazine fed M870; China’s Hawk Industries has already accomplished that task and currently producing the Type 97-1. This model is an imitation of the Remington pump action shotgun and available with a pistol grip and side folding stock as well as a bullpup version. These guns have single stack detachable 5-shot box magazine. A new super compact version of this model is imported into Canada featuring an 8 inch barrel and a fixed stock to meet the minimum legal overall length of 26 inches. Their current compact model features 12.5 inch barrel with a fixed stock. Importation of these guns to North America is handled by Norinco Industries.

For folding stock provision, three parts from Ace Limited will be required. This items include the Folding stock mechanism (FSM), the matching AR-15 receiver block (ARRB) and the CAR-15 stock block (pig nose). The ARRB is first installed to the rear of the CAA grip/stock adapter as you would do on an AR rifle, followed by the usual receiver end plate (bottom end cut off to blend with the underside contour of the CAA adapter). The castle nut tightens the assembly of the ARRB to the adapter with the top end of the Ace part flush with the castle nut. The folding stock mechanism is then assembled to the ARRB with the supplied hardware. Next step is to install the pig nose to the folding stock mechanism with the supplied assembly screws. The CAR style extension tube can now be assembled to the pig nose and then tightened in place by a castle nut once the stock is correctly lined up with the grip and rear sight from the rear. You may install the pistol grip to the CAA adapter before or after you have completed the stock assembly. Installation of back-up sights to the shotgun will require these two components. One is the CAA barrel shotgun rail (SGR-1). This two-piece CNC machined aircraft grade aluminium part is normally assembled to the front end of the barrel like a clamp with the rail facing down to accommodate a laser or light. In the CATS set up, this part is assembled to the end of the barrel with the rail facing up to act as a front sight mount. The lower section of the SGR-1 (without the rail) will need to be trimmed down in circular pattern in order to clear the diameter of the knurled section of the Scatter Gun Technology 1-shot extension tube. This will allow unimpeded assembly and disassembly of the extension tube if needed. The 1-shot extension serves as a mount for the LaserLyte tri-rail accessory mount. This accessory primary serves as a bipod mount for accurate slug placement at longer ranges. The side rail can also accommodate a mini laser device if you can find one that can take the vibration of a 12 gauge being mounted at the right beside the muzzle. The second component needed is the matching rear sight mount. A saddle type scope mount is ideally suited for this purpose. There are several brands of scope mounts available for the M870 made by Remington, Aimtech, Mesa Tactical, UTG and others. They vary in prices, quality and styling. For this requirement, I found the UTG to be the ideal match for the CAA SGR-1. It is economically priced, has great aesthetics and appears to be well made and finished. Assembly of this part simply requires removing the two factory trigger housing pins and replacing it with the UTG supplied hardware. Because the height of the UTG and SGR-1 is not quite perfect on the gun, the right combination of BUIS must be carefully selected in order for the sights to co-witness precisely. For the rear, any AR A2 style sight with elevation adjustment will do such as the DPMS or Lewis Machine tactical rear sights. These are fixed style sights but they leave enough room on the saddle rail for compact optic installation. For folding style sight, the ArmaLite .308 flip up was perfect. This sight is slightly taller than standard .223 flip up sights. This BUIS features a rotating disk for elevation setting and is very well made. Unfortunately, ArmaLite has since discontinued the production of this BUIS. The next step is to find the front sight that will co-witness precisely with the rear. Pro-Mag’s gas block mounted AR-15 flip up sight prove to be the ideal match for the ArmaLite rear sight. Gas block mounted sights may vary in height depending on the manufacturer. If you are using an A2 style rear sight, its elevation adjustment will accommodate more dimensional tolerance between brands so you can use any gas block mounted AR-15 rear sight made for the .223 caliber. The Leatherwood Hi-Lux 3.5 MOA perfectly complemented this tactical package. This high resolution red/green dot scope is fully waterproof and shockproof. It comes with integral mount, flip-up lens cover and rubber lens guard. The Model ES1 X 30TP retails for under $100 and it’s a bargain for a rugged lightweight compact scope that can take a beating with hard use.

Although there are many after-market forearms available for this gun made of aluminium and polymers, I elected to utilize the original factory part which I found to have the best fit and it is slimmer than most after-market forearms with built-in rails (except Magpul). However, the Magpul M870 forearm will prevent installation of a heat shield being made higher than the stock part, therefore, it is not chosen here. The only thing I added is the ultra-thin Yankee Hill Machine 7-inch customizable rail at the bottom of the factory forearm to accommodate a forward grip and light. The top front end section of the forearm will require some trimming to clear the CAA SGR-1 rear bottom loop to allow full closing of the action. When the matching heat shield is installed, its bottom side will rest snuggly with the top of the forearm thus preventing wiggle or side to side movement of the part for a solid feel yet very smooth to operate when pumped. Depending on one’s personal choice, I for one like to utilize a forward grip for better control particularly with a shotgun. I can adjust my reach at a very comfortable level with a pump action gun much like adjusting a collapsible stock. The market is currently flooded with all type and sizes of forward grips to include fixed, folding, stubby, long, flat or round and many more in between. I have over a dozen of these accessories made by various companies and after trying them all on this project gun, I have narrowed down my choice to MFT grips; namely their REACT Torch and vertical grip (RTG) and Ergonomic Vertical Grip (REG) as the perfect match for the tactical compact shotgun package. The RTG is a combination of vertical grip and illumination mount. This beautiful grip has many cool features. It can accommodate three popular sizes of lights from 3/4 to 1 inch in diameter including laser device for night application. It has a built-in secure no-rattle storage compartment and grooved gripping surface similar to that found on custom heat stippling for a solid non-slip grip. Their full size vertical grip is tailored for medium to large hands and is a perfect match for the Engage AK-47 pistol grip. Both of these grips features finger-groove pattern and the textured gripping surface is strategically incorporated around the grip to get the most benefit from a comfortable non-slip hold. To date, MFT have designed and produced some of the finest AR and AK furniture in the industry. These are truly outstanding products with amazing ergonomics and original futuristic styling. Overall, I strongly believe that MFT has the edge over its competition especially in formulating new ideas in creating their state-of-the-art weapon accessories. This is no secret when you take into consideration that the company’s design philosophy is based on heavy input from professional weapon operators from around the globe to bring about the most technically advance weapon upgrades that easily met and exceeded military and law enforcement requirements.


Mission First Tactical:
CAA Command Arms:
Yankee Hill Machine:
Fab Defence:
UTG Tactical:
ACE Ltd.:
Wolverine Supplies: (Canada)


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