M412 "Tactical Road Blocker"
By J.M. Ramos

Never before have so many shooters and collectors become so interested to learn how to create their own dream guns with the aid of modern accessories. This is rightly so because it has never been so easy to install these magnificent accessories and the selection available is mind boggling. To complement the M412 article published previously in SAR that covered the compact CQB version of the Remington M870 shotgun, this article is focused on power and precision while keeping the well established tactical format so revered by today’s modern battlefield warriors. While the weapon configuration presented in this project is geared primarily for law enforcement and military applications, it is also ideally suited for civilian defense and tactical sport shooting competitions. The writer designated the project gun as “Tactical Road Blocker” simply because that is exactly what it is being designed to accomplish. Road blocks are normally set up by police to corner a fleeing felon who in most cases drives a motorized vehicle. Often the driver of the target vehicle will try to ram through the blockade and create damage to police vehicles or in some cases cause serious injuries to the officers manning the block. Patrol officers are normally issued with service handguns and a 12 gauge riot shotgun. Riot type police shotguns are not equipped with precision sights since they are normally used as short range buck shot spreaders.

Law enforcement strategists are constantly looking for more effective ways to improve their policing techniques in order to save lives and property. Tools of their trade are unquestionably a vital importance in being able to accomplish their dangerous tasks effectively and efficiently. The shotgun has for over a century been the most favored tool by American lawmen and security couriers of the old west. That well established tradition continues to this very day; clear proof that scatterguns are truly unbeatable as a close quarter combat arm wherein multiple numbers of projectiles are discharged with a single fire. The development of more lethal ammo and rifled barrels for this new generation of arms has made the 12 gauge even more attractive as a duty or a hunting arm. Although primarily employed as a scattergun, shotguns can now perform as a precision big-bore rifle when equipped with a rifled barrel. A 3-inch Magnum with a one ounce slug is now capable of 2,000 fps muzzle velocity. This is quite powerful when used as a precision road blocker. A good reloader can further enhance the Magnum power of the big round well beyond the factory loads for more destructive capability: enough to blow away an engine block using special exploding projectiles or steel penetrators that can instantly disable an engine upon impact. An officer equipped with this arm will have a much better chance of taking down a suspect vehicle before it can create havoc to police cars or hurt anyone before it impacts the road block. To accomplish this task, a special type of arm must be devised. The M412 Tactical Road Blocker is an attempt to create such a weapon system using available tactical accessories that can be easily put together by police or military armorers to become standard equipment for road blockers utilizing the proven Remington M870 action as a starting point.

What’s Required

As clearly stated, this is a specialized gun for extreme situations. Although nothing would probably beat the .50 caliber rifles now available as the ultimate car stopper, this is simply not the ideal hardware for the urban environment. Therefore, the next big thing is a 12 gauge shotgun in 3-inch Magnum or larger. Since the primary target is the vehicle, the choice of ammunition is extremely important for the round to do the most damage to the engine or tire. Tests at different distances must be undertaken to determine the effective ranges in order to give the operator the idea when to fire to the incoming target vehicle and what damage to expect when the moving target is hit at a certain point. The 12 gauge Tactical Road Blocker weapon system being equipped with optical sight, rifled barrel and bipod can be fired like a precision rifle at the intended target and those big slugs can do a better job more safely than an AR or AK within 50-100 meters - especially when bystanders are nearby.

The M412 Tactical Road Blocker is basically the same Remington M870 used in the CQB versions but with a longer factory 20-inch rifled slug barrel complemented by an 8-shot capacity using a magazine extension. A shorter 18-inch cylinder barrel version can also be employed allowing both buck shot and slugs to be fired. This will have a capacity of 7-shots using the factory magazine extension as employed in their tactical gun series. These replacement parts are readily available from sporting goods or gun stores or mail order outlets like Brownells. For furniture, The CAA RS870 M4 buttstock/pistol grip assembly remains the author’s top choice. This accessory is the most authentic among this type of accessory that are currently available for this gun in the market. The AR’s straight stock format affords comfortable shooting stance and milder recoil absorption. For a more compact requirement utilizing the 18 or 20-inch barrels, folding stocks are available. One of the classic folders originally offered back in the 80s is still produced today by Choate but shorter in length. However, the Choate design still retains the original sloping pattern as opposed to the most desired modern straight stock format for high sights and optics thus exhibiting more pronounced muzzle flip and heavier felt recoil. An ideal folder that can work in conjunction with the CAA RS870 pistol grip and stock base is the Ace AR15 FX folding stock. The FX folder is patterned after the famed FAL Para design but much improved in a sense that it can be set up to be folded either to the left or to the right side of the gun. When the stock is in the extended position, it provided a straight stock format perfectly working in harmony with the AR high sights or optics. It also offers less felt recoil and enhanced ergonomics. The overall quality of the metal stock is excellent and quite robust in overall construction. Ace made good use of their Para side folders by creating numerous adaptors to fit varieties of popular arms to include the AR, AK, SIG 550, FAL, Saiga, Daewoo and even the Ingram M11 machine pistols; just to name a few. The machined aviation grade aluminum of the RS870 stock base is assembled to the M870 receiver by the usual stock screw. The rear of the CAA part has been bored and threaded to accept the matching AR buttstock tube that came with the kit. This threaded opening will also connect to the front end extension of the Ace FX folding stock base where the stock itself is fastened using two large socket head screws. If the operator wishes to install a side saddle shell holder to the gun, the best section to put it is on the right side of the skeleton stock. The shell holder made by Tac Star is ideal for this set up. It has a loop for six rounds and features an aluminum back plate which can be drilled through over the plastic part to connect to the matching (threaded) assembly hole of the aluminum tubing of the stock. Four 6-32 socket head screws assembled on both ends of the shell holder is more than enough to secure the part in place.

Standard AR or BUIS sights can be incorporated to the Road Blocker using the appropriate mounts. For the rear sights, the B-Square receiver saddle scope mount is ideal. It’s the longest available that can accommodate the length of the AR carry handle type sight and features the popular Weaver type rail. For the front sight installation, the CAA Shotgun Rail Adaptor (SGRI) is a perfect mount. The Israeli made accessory features a fully machined high quality aluminum construction utilizing a unique dual clamp design with the two halves connected to a short Picatinny/Weaver type rail on each end. The lower two halves of the clamp tightens the assembly to the front end of the barrel using four screws. A BUIS type sight is then mounted to the rail as usual. The SGRI is a very solid and attractive sight mount originally designed by CAA for mounting lights, laser or bipod but it is also perfect for iron sights installation as used in this project. There are now many tactical type forearms for the M870 available with built-in rails for mounting forward grips, lights, laser, etc. These are mostly polymer in construction and quite affordable. If you want a first rate Tri-rail aluminum Picatinny rail forend, the Wilson tactical version is true to its reputation: a workhorse accessory that commands a high price tag. One of the drawbacks noted on this tri-rail accessory is its bulk. A forward grip is definitely a must for those with small or even average size hands to grasp around it. For forward grip requirement, the CAA VG1 Combat grip remains the author’s favorite. It’s a perfect combination for the UPG47 finger groove pistol grip used in the RS870 stock. The Carry Handle sight (CH) selected is again a CAA product and is a quality part that is surprisingly affordable. Matching the Carry Handle sight is the DPMS steel detachable front sight in the classic AR front sight configuration. For those who may prefer a low profile BUIS back up sight, the popular YHM Rear Flip and forearm flip sight (not gas block front flip sight) is an ideal combination for correct sight level format. The YHM sights are well designed and economically priced and an excellent value in this category. The Carry Handle sight features elevation and windage adjustments as well as further elevation adjustment for the front sight post if needed. With this type of sighting system, the rifled shotgun with a 20-inch barrel can be fine tuned to an outstanding accuracy never before experienced with this type of hardware specially when mounted in a bipod such as CAA’s three-position heavy duty bipod system. Perfect for this set-up is the Bipod Short Length (BPOS). The pods can be folded neatly on the lower side of the forearm or forward when not in use. The design of this accessory is truly outstanding. It’s compact, sleek and revolutionary with all mechanical components being self contained within the pods. It’s one of the best bipods ever produced for tactical long arms. There are two ways to mount the bipod to the gun. One is to the forearm assuming it has a bottom rail. This will require a different way of cycling the action of the gun during the firing sequence. With the bipod planted to the ground or on top of the hood of a vehicle, the operator will hold firmly on to the forward grip and maintain a steady hold via a downward pressure against the bipod. While firing, both the forearm and bipod remains steady, but the entire gun will move along with the shooter’s body as the gun is rocked back and forth during the reloading sequence by the action of the rear pistol grip being push forward to eject the fired shell and then pulled backward to reload. This sequence of operation is undertaken while the shooter’s shoulder rests steadily in the buttstock while maintaining sight alignment at all times. It’s actually a unique and surprisingly fast and accurate shooting technique for a pump action shotgun with a forward grip and a bipod mounted on the forearm.

For the more traditional set-up, there are two gadgets that can be acquired and installed to the magazine extension where a rail mounted bipod such as the CAA BPOS can be installed directly. Bipods that are designed to be installed to a sling swivel stud, such as the Harris brand, can also be installed on this accessory using the CAA Universal Accessory Mount. The 3-rail Picatinny shotgun mount made by Lite Mount Technologies is designed primarily to be assembled to the magazine extension. The bottom rail will take a bipod and the two side rails are for lights or laser or any other small tactical accessory. Another accessory that can function as a bipod mount for those who would prefer less bulk is the single rail accessory mount made by Tactical Night Vision. This accessory is primarily designed as a one inch scope or laser mount but the author found it to be perfect as a bipod mount as well when mounted to the magazine extension tube.

Finally, when its time to choose optics, lasers and lights, the ultimate choice is for the end user to decide: with many amazing sighting devices to choose from depending upon the need. If this M412 Tactical Road Blocker is to be put to a specialized role to save lives and property, it is fitting to get the best sighting system and trigger work to maximize its true tactical capability now that its ergonomics and handling characteristics has been optimized.


Command Arms Accessories (CAA)
76 Vincent Circle
Ivyland, PA 18974

Brownell’s, Inc.
200 South Front Street,
Montezuma, Iowa 50171
www. Brownells.com

This article first appeared in Small Arms Review V13N12 (September 2010)
and was posted online on March 9, 2012


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