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Thread: The R18 Mk2 Review Pt 1 - Initial Details and Pre-Firing Impressions

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    Super GunNutz Bartok5's Avatar
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    The R18 Mk2 Review Pt 1 - Initial Details and Pre-Firing Impressions

    I must admit from the outset that I was excited by my first look at the R18 Mk2. From what I could see, somebody had finally combined the familiar ergonomics that AR owners have been missing, with the AR-180B operating system by utilizing a streamlined and integrated aluminium upper and lower receiver set. The WK-180 and WS-MCR brought us part-way to this point, with the aftermarket Spectre Ltd “Spec” Lower and other custom Upper and Lower Receivers offering additional, incremental improvement. The R18 completes the concept in a relatively svelte and visually appealing package that oozes refinement over its AR-180B-styled predecessors. Looks are all well and good, but what about performance? We’ll get to that, but first let’s see what we can derive from appearances and a bit of background provided by the retailer, James R. (JR) Cox, of The Shooting Edge (TSE) in Calgary, AB.


    Right Side View:




    First however, full disclosure regarding my relationship to Sterling Arms International and JR Cox. As regards Sterling Arms, I once owned one of their ill-fated AR-10 rifles, which was an excellent firearm by all accounts. I sold it, and then the OIC Ban Hammer fell on May 1st 2020 rendering those rifles and their 5.56mm counterparts as “Safe Queens”. That is the full extent of my relationship with Sterling – we have no relationship. JR Cox on the other hand, I know quite well. We served in the same Army Airborne Light Infantry Unit (3PPCLI) a lifetime ago and shared some adventures under parachutes as well as heavy rucksacks in the mountains! You could say that JR and I are friends, but not super close. I agreed to test the R18 Mk2 out of personal interest, nothing more. JR, knowing that I am a “gun guy”, reached out and made the arrangements. I am in no way beholden to JR Cox and am not associated with his businesses in any way shape or form – aside from the fact that I shop in The Shooting Edge (TSE) whenever I happen to visit Calgary. All of that to say that you will get an honest review out of me – no polishing of turds will occur on my watch…


    Left Side View:




    The introduction of the R18 Mk2 is by no means JR Cox nor Sterling Arms International’s first foray into the risky Canadian firearms manufacturing business. As mentioned, they introduced new Canadian/UK manufactured AR-10 and AR-15 style firearms to the Canadian market immediately prior to the infamous 1 May 2020 mass prohibition. As a result of that OIC, JR was left a considerable investment in stock of over 500 unsalable .308 and .223 Receiver sets manufactured by Sterling, UK, which are still collecting dust on a TSE shelf. Never one to rest nor cry over spilt milk, JR (like others) recognized a further opportunity in the non-restricted AR-180B semi-automatic platform. However, instead of bringing another low-budget iteration of the AR-180B to market, JR’s vision was more upscale. He envisioned SAI providing to his organization a blending of familiar AR-style ergonomics with the AR-180B’s operating system, while ensuring no receiver compatibility with existing AR 10 or 15 firearms. The new firearm would be nicely contoured and surface-finished as compared to the lower-budget competition. It would command a somewhat higher price, commensurate with the increased machine time and surface preparation required to produce a smooth, rounded and properly Hard-Coat Anodized external finish. SAI believed they were up to this challenge.


    Manufacturer Information - 100% Made in Canada:




    Working from the front end back, we first encounter a custom Bird-Cage style combination Muzzle Brake and Flash-Hider on a standard ˝ x 28 thread. The SAI 18.6” Barrel is precision CNC-machined in Canada from premium GB CrMV Steel Blanks that are button-rifled 6-groove with a 1/8” twist rate, lapped and stress-relieved. The “Pencil” profile blanks are air-gauged during final inspection and feature a precision-cut Chamber, Gas Port and an 11-degree “Target” Crown. The .223 Wylde Chamber safely accepts both .223 Rem and 5.56x45mm NATO ammunition. In designing the R18 Mk2 Barrel, SAI took a page from Heckler & Koch’s playbook and gave the Chamber an Extended Root to limit flex and add strength. The Barrel is QPQ Nitride treated inside and out with the portion forward of the Gas Block Linear-Fluted to maintain rigidity while aiding in cooling and removing fore-end weight.


    SAI Combination Flash-Hider & Muzzle Brake:




    The Barrel is secured to the Upper Receiver by a somewhat unconventional “Sandwiching” system similar to that used by Daniel Defence for certain models such as the DD5 .308 rifle. The unique Barrel Nut features a Flange that is secured to a matching surface at the front of the Upper Receiver by 4 large bolts. The AR15-compatible Barrel Extension is “sandwiched” between the Barrel Nut’s flange and the front of the Upper Receiver. The four Barrel bolts are threaded into steel Heli-Coils embedded in the aluminum Upper Receiver so as to avoid stripping the threads. The Barrel attachment system is believed by the developers to enhance the overall accuracy potential of the rifle. We shall see about that. The other advantage of this particular Barrel mounting system is that AR-compatible barrels with a standard Rifle-length Gas Port are easily swappable by the home gunsmith. Install a heavier profile AR Barrel and you can create a “Precision” 5.56mm/.223 rifle right in your own hobby room.


    Barrel Nut and "Sandwiching" System:




    The Rifle-length Gas System consists of a short-stroke piston based directly upon the AR-180B design, with a .750 Gas Journal. The non-adjustable Gas Block is secured to the Barrel by 2 Allen (Hex) Screws on the underside. The Gas Block and Piston System are hidden from view and touch by an aluminum handguard with an interrupted 1913 Picatinny Top Rail and MLOC slots at the 3, 6 and 9 o’clock positions. The lightweight aluminum Handguard is currently affixed to the proprietary Barrel Nut by a series of four screws which must be removed in order to slide-off the Handguard and access the Gas System for maintenance. This shortcoming has already been identified by SAI and a QD Handguard design is already in development for the Mk3 version of the rifle, which I am told is on the drawing board. Removal of the Handguard is a simple matter and Alignment Tabs make re-installing the tube a simple matter. Just be careful not to cross-thread the screws in the Aluminum threads when replacing them.


    Barrel and Gas System:




    Moving back from the Trunnion area, we have an enhanced AR-180B-style Upper Receiver mated to a hybrid Lower Receiver with matched contours and that oh so familiar suite of AR-style controls. Indeed, seeing no need to reinvent the wheel, SAI adapted generic AR controls within the proprietary Lower Receiver such as the Bolt Catch, to work with the AR-180B-based Upper Receiver. Of course, not just any old Bolt Catch would do, so a custom Geissele “Maritime” style catch with extended pressure-pads was adopted for the Left side of the R18 Mk2 Lower Receiver. Another very welcome addition to the R18 Mk2 suite of controls is an integrated Bolt-Release on the Right side of the Lower Receiver. This feature allows the user to release the Bolt Carrier and Bolt forwards under spring pressure using only the Trigger Finger (rather than the Support Hand). Note that the R18 Mk2 Lower Receiver is not compatible with AR15 Upper Receivers, nor wil an R18 Upper Receiver mate to an AR15 Lower as the two rifles share no design commonality besides the use of some generic controls, parts and ergonomics.


    Upper and Lower Receiver - Left Side:




    The Lower Receiver features a nicely flared Magazine Well and an integrated Trigger Guard. It accepts generic AR Pistol Grips with a Beavertail and features a 1913 Picatinny Rail on the rear end for attaching a compatible Buttstock or an Accessory Plate. The Pistol Grip provided with the R18 is the Grey, rubber-coated Magpul MOE-K2+ with its comfortable, reduced grip-angle. The ambidextrous Selector Lever is the standard Sterling fare and those who own one of the earlier Sterling “safe queens” will immediately recognize it. The Selector activation is not overly stiff but has positive detents in the "Safe" and "Fire" positions. Although the Selector and Bolt-Release are ambidextrous, the Magazine Release is not. A Norgon-style Magazine Release would easily address that minor shortcoming for those who prefer a Magazine Catch on the Left Side of their rifle. The Magazine Release is adequately protected from accidental activation by the contours of the Lower Receiver. The rear-most pocket in the Lower Receiver is fitted with a Tensioning Screw which places pressure on the bottom of the Upper Receiver to effectivey remove slop between the two Receiver halves. This system is identical to that employed by Aero Precision for those familiar with those Receivers.


    Lower Receiver - Left Side:




    The stock trigger is 100% “Mil-Spec” AR15. It is single-stage, fairly smooth with a crisp, clean break at an average of 6.5 lbs pull. Reset is not too bad. You be the judge, but I exchanged the stock Trigger in my sample rifle for an adjustable Trigger Tech aftermarket unit. Night and day! The R18 Lower Receiver is specifically engineered to accept the Canadian Trigger Tech after-market, custom Trigger pack with user-adjustable Trigger pull-weight. Geissele Triggers ought to also work, along with most brands of after-market Trigger be they the cassette-type or the separate Hammer and Trigger set-up. With the R18 the maker and type of after-market Trigger is your call….


    Lower Receiver - Right Side:




    Turning to the Upper Receiver, the most notable feature is the Left-side, non-reciprocating Charging Handle very similar to that of the old-school FN FAL. The length of the sliding Charging Handle itself acts as a cover over the Cocking Slot, effectively sealing the rifle’s internals against ingress of foreign matter. The Right side of the Receiver mates closely with the side of the Bolt Carrier to also thwart the ingress of dirt and debris. The Mk3 version of the R18 will include the familiar AR-15 style of Ejection Port Cover. It will not be possible to retroactively fit the Dust Cover to the Mk2 Rifle, not that it is considered necessary in the first place. The Ejection Port Cover is expected to be on the Mk3 to satisfy potential LE clients who may insist on the additional safeguard against foreign matter. The steel Charging Handle operates smoothly and the aluminum Charger bar slides in a thick aluminum Receiver Rail which should result in nominal wear. The Cocking Handle is by necessity situated high up on the Left side of the Upper Receiver and some interference with certain optic mounts or rings may be unavoidable. SAI has attempted to mitigate this shortcoming with the use of an extended Cocking Handle which has the added advantage of providing additional purchase area for added leverage when extracting a sticky casing. As currently designed, the Cocking Handle does not double as a Forward Assist for silent chambering of a cartridge. The utility of a Forward Assist is debatable, however if the option exists to have one it would be a welcome addition. The non-reciprocating Cocking Handle is retained by a spring-loaded ball-bearing in the Cocking Knob mated to a detent in the Upper Receiver. The ball-bearing’s tension can be adjusted to compensate for any eventual wear to the Receiver Detent and the Detent itself could always be drilled deeper into the beefy Upper Receiver wall if eventually necessary.


    Cocking System:




    Purchasers of the R18 Mk2 will receive a rifle with a Fixed tubular Receiver Extension and a Gray Magpul CTR Buttstock. The Mk3 version expected will feature the Magpul Zhukov Folding Buttstock, which will also be backwards-compatible with the earlier Mk2 rifle. Both Buttstock options accept Cheek-Risers and come with QD Sling cup options. The Zhukov stock will allow the R18 to be fired with the stock folded a-la the 1980s, or with the Buttstock extended for maximum stability and accuracy. As far as the Mk2 is concerned, the non-folding Tubular Buttstock is extremely comfortable with a solid cheek-weld – just as you would expect from Magpul. Of course, with the Rear Picatinny Buttstock attachment system any Buttstock that is so equipped can be mounted. I have a “Safe Queen” SIG MCX which temporarily donated its Folding/Retractable Buttstock to the R18 Mk 2 just to see if it could be done and it was no problem.


    Buttstock Interface:




    The Picatinny attachment for the Buttstock means that in theory, the Stock height can be adjusted to suit the firer’s individual preferences. However, as currently manufactured the rear Picatinny Rail is quite short and adjustment from the center position will leave a portion of the Buttstock clamping system hanging over empty space. It is my belief that the Picatinny Rail should be extended one more increment upwards on the rear of the rifle so that additional adjustment can be made to put the Buttstock slightly over the line of the Barrel. This would serve to reduce any muzzle-flip as well as bringing the cheek-weld a bit higher and possibly more comfortable for certain optics users.


    Buttstock Interface 2:




    Users will want to note that the Buttstock’s Picatinny clamping system adds approximately 3.5 cm of non-collapsible length to the Receiver Extension. It is also worth noting that with the Picatinny system it is currently not possible to attach an unmodified A2-style solid stock. I have been told that SAI will have an adapter shortly for this. That also said, Midwest Industries in the States produce a variety of different stock styles with the same Picatinny interface, which is definitely the way of the future for attaching different Buttstock options.


    SIG MCX Buttstock Fitted to R18 Mk2 Picatinny Interface:




    Its various features notwithstanding, how does the R18 handle? The balance point is directly in front of the Magazine Well, which is ideal for weight distribution when carrying and shouldering the firearm. Equipped with Iron Sights alone, the R18 Mk2 feels very lightweight and “lively” in the hands. It is quick and thanks to the familiar ergonomics, comfortable and natural to point at a target. The head-height and cheek-weld are excellent for both Irons and Optics and can always be adjusted up or down slightly using the 1913 Picatinny rail on the rear of the Lower Receiver. The R18 weighs 3.6 kg or 7.9 lbs unloaded, “naked” from the factory. (By way of comparison, a WK180 is approx. 7.3 lbs)

    The Action is very smooth, which makes sense given that the Bolt-Carrier is riding on two polished steel rods inside the Upper Receiver. Each of the rods features an Operating Spring which combined provide ample forward force to strip a new cartridge and close the action at the end of the firing sequence. Standard AR-180 fare here folks, through and through. The Bolt is Nitrited Carpenter Steel and is (of course) Pressure and Magnetic Particle Inspected. Proof rounds are fired as part of the pre-shipment test-firing QC process.


    Bolt Carrier and Bolt:




    Stripping and reassembly of the R18 Mk2 are both simple and intuitive for anyone familiar with either the AR15 or one of the AR-180B designs currently on the market (The rifle does come with a downloadable manual). Simply push out the Rear Take-Down Pin and slightly depress the Rear Plate of the Recoil Assembly which will allow the Upper and Lower Receivers to pivot open and away from each other. If you wish to fully separate the Receivers simply push out the Front Take-Down Pin and the Upper and Lower will come apart. From there the Upper Receiver can be further stripped by racking the Cocking Handle and withdrawing the Bolt Carrier/Bolt/Guide Rod/Operating Spring Assembly from the Upper Receiver. From there, the Bolt Carrier and Bolt can be easily separated from the Guide Rods and Operating Springs by simply pulling. Removing the Bolt from the Carrier is a matter of pushing out the Firing Pin Retaining Pin from Right to Left on the Carrier, removing the spring-loaded Firing Pin from the rear of the Carrier, Removing the Cam from the Left side of the Carrier, and finally pulling the Bolt out of the front of the Carrier. Detailed stripping of the Bolt itself (eg. Extractor and Pin) is the same as any AR-pattern rifle.


    Field-Stripped R18 Mk2 (Note that the Factory Trigger has been replaced by my TriggerTech for Accuracy testing):




    Reassembly is simply done in the reverse order. Ensure 2 things as you proceed with reassembly:
    1. Depress the rear of the Firing Pin when re-inserting the Firing Pin Retaining Pin, and
    2. Make certain that the Operating Springs are fully seated within the Bolt Carrier by pushing the Carrier down along the Guide Rods (simulating the ejection cycle) until the Springs become visible in their holes at the front end of the Carrier.

    The Gas System need not be serviced every time the R18 Mk2 is Field-Stripped for maintenance, however it is also rather easily accomplished. Once you expose the Gas System by removing the previously mentioned four Handguard Screws and the Handguard itself, stripping the actual parts is a relatively simple matter. Pull downwards on the long Push Rod, compressing the Spring. This will create sufficient space near the front of the system to withdraw the central Spacer. Once the Spacer is removed, simply pull the Piston Cup down off of the Piston/Gas Block. Reassemble in the reverse order.


    Gas System Field-Stripped:




    A potential show-stopper for some will be the fact that the R18 Mk2’s Upper and Lower Receivers are fabricated from T6061 aluminum alloy, and not the harder T7075. I don’t have a dog in this fight and understand that there are pros and cons associated with the use of each material. At the end of the day, JR noted that T6061 is easier to cut and therefore requires less expensive machine time to fabricate each component. Added to that is his belief that the more ductile T6061 will withstand the explosive forces of a detonation out-of-battery better than the more brittle 7075-series counterpart. He may have a point there, not that anyone is anticipating breech explosions in the R18! In any case, the Sterling Arms International AR10 that I owned for a brief time was fabricated from T6061 as well, and there were no issues arising from use of the slightly softer alloy.


    Upper Receiver - Top View w/ 14" Handguard:




    The Finish on the R18 Mk2 is a combination of matte black Type III anodizing on the 6061 Aluminum and QPQ Nitride on the steel components with what appears to be Parkerizing on some small steel parts. I note that the anodizing does not appear
    to be all that thick/durable as both rifles received for testing had exposed aluminum on the sharp edges of the Brass Deflector after firing approximately 300 factory test rounds following assembly. Sterling’s Canadian Operations Manager related to me that there had been some difficulty in obtaining consistent anodizing colour from sub-contractors early in the production process, so it stands to reason that the anodizing system may still be tweaked as the R18 Mk2 enters full production.


    Lower Receiver - Top View (Note that my TriggerTech Trigger is installed for Accuracy Testing):




    Speaking of production rifles, a couple of minor issues have surfaced with the initial batch of 17 to come off the assembly line in Calgary thus far. In the first instance, the front face of the Bolt Carrier does not extend far enough forward to prevent
    the Extractor Retaining Pin from backing out, which can jam the Bolt in the forward position leading to a stoppage. This will be rectified by extending a small “raised collar” on the Bolt Carrier around the Bolt body, thus covering the Extractor Retaining Pin and preventing it from backing out. The second issue has to do with the length of the Rail within the Upper Receiver that controls the Bolt locking and unlocking process. The rail is slightly too short towards the rear of the Upper Receiver, which can make re-inserting the Bolt and Carrier into the rifle more difficult than it need be. Both of these minor fixes will be addressed as rolling changes going forward.

    So now the big question – how does the R18 Mk2k shoot? Tune in for Part 2 of my Review in a few days’ time after I’ve had a chance to hit the range….
    Last edited by Bartok5; 11-06-2021 at 03:49 PM.
    Mark C

  2. #2
    Member GlowInTheDark's Avatar
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    Thank you for this!

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    CGN Ultra frequent flyer scott's Avatar
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    Pic with bolt held open? Does the sliding cover stick out the back when open?

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    GunNutz
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    Nice

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    Super GunNutz Bartok5's Avatar
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    Quote Originally Posted by scott View Post
    Pic with bolt held open? Does the sliding cover stick out the back when open?
    The "Sliding Cover" of the Cocking Handle only projects past the rear of the Upper Receiver when you manually charge the firearm. Once you ock the Bolt-Carrier to the Rear and push the non-reciprocating Cocking Hande back to its forward position, it remains there regardless of the subsequent position of the Bolt and Carrier. That is what the spring-loaded Ball Bearing in the Cocking Handle and the corresponding Detent in the Upper Receiver are for....
    Mark C

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    Member Bruh101's Avatar
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    Holy #### im definitely getting one, guess im not going to need to eat for the next 3 weeks

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    CGN Regular AntiKhaos's Avatar
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    Looks pretty good, honestly the only downside I see is with the rail.
    Personally I like scalloped top rails but you can't deny that process does permanently reduce the amount of top rail space.
    Not a big issue for most people but for people with NV/IR gear you want that room.

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    CGN Regular Tractorguy's Avatar
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    Great job and thanks for the work, will be paying attention to this thread. Let’s go Brandon - Let’s go surfing

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    CGN Regular 3CDO's Avatar
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    Very good description of the rifle. Peaks my interest. Looking forward to the review on the functioning of the rifle.
    If you can't be out of sight, you best be out of range.
    GOTO retailer NORDIC MARKSMAN

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    CGN Regular Ceiferiro's Avatar
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    Quote Originally Posted by Bartok5 View Post
    I must admit from the outset that I was excited by my first look at the R18 Mk2. From what I could see, somebody had finally combined the familiar ergonomics that AR owners have been missing, with the AR-180B operating system by utilizing a streamlined and integrated aluminium upper and lower receiver set. The WK-180 and WS-MCR brought us part-way to this point, with the aftermarket Spectre Ltd “Spec” Lower and other custom Upper and Lower Receivers offering additional, incremental improvement. The R18 completes the concept in a relatively svelte and visually appealing package that oozes refinement over its AR-180B-styled predecessors. Looks are all well and good, but what about performance? We’ll get to that, but first let’s see what we can derive from appearances and a bit of background provided by the retailer, James R. (JR) Cox, of The Shooting Edge (TSE) in Calgary, AB.


    Right Side View:




    First however, full disclosure regarding my relationship to Sterling Arms International and JR Cox. As regards Sterling Arms, I once owned one of their ill-fated AR-10 rifles, which was an excellent firearm by all accounts. I sold it, and then the OIC Ban Hammer fell on May 1st 2020 rendering those rifles and their 5.56mm counterparts as “Safe Queens”. That is the full extent of my relationship with Sterling – we have no relationship. JR Cox on the other hand, I know quite well. We served in the same Army Airborne Light Infantry Unit (3PPCLI) a lifetime ago and shared some adventures under parachutes as well as heavy rucksacks in the mountains! You could say that JR and I are friends, but not super close. I agreed to test the R18 Mk2 out of personal interest, nothing more. JR, knowing that I am a “gun guy”, reached out and made the arrangements. I am in no way beholden to JR Cox and am not associated with his businesses in any way shape or form – aside from the fact that I shop in The Shooting Edge (TSE) whenever I happen to visit Calgary. All of that to say that you will get an honest review out of me – no polishing of turds will occur on my watch…


    Left Side View:




    The introduction of the R18 Mk2 is by no means JR Cox nor Sterling Arms International’s first foray into the risky Canadian firearms manufacturing business. As mentioned, they introduced new Canadian/UK manufactured AR-10 and AR-15 style firearms to the Canadian market immediately prior to the infamous 1 May 2020 mass prohibition. As a result of that OIC, JR was left a considerable investment in stock of over 500 unsalable .308 and .223 Receiver sets manufactured by Sterling, UK, which are still collecting dust on a TSE shelf. Never one to rest nor cry over spilt milk, JR (like others) recognized a further opportunity in the non-restricted AR-180B semi-automatic platform. However, instead of bringing another low-budget iteration of the AR-180B to market, JR’s vision was more upscale. He envisioned SAI providing to his organization a blending of familiar AR-style ergonomics with the AR-180B’s operating system, while ensuring no receiver compatibility with existing AR 10 or 15 firearms. The new firearm would be nicely contoured and surface-finished as compared to the lower-budget competition. It would command a somewhat higher price, commensurate with the increased machine time and surface preparation required to produce a smooth, rounded and properly Hard-Coat Anodized external finish. SAI believed they were up to this challenge.


    Manufacturer Information - 100% Made in Canada:




    Working from the front end back, we first encounter a custom Bird-Cage style combination Muzzle Brake and Flash-Hider on a standard ˝ x 28 thread. The SAI 18.6” Barrel is precision CNC-machined in Canada from premium GB CrMV Steel Blanks that are button-rifled 6-groove with a 1/8” twist rate, lapped and stress-relieved. The “Pencil” profile blanks are air-gauged during final inspection and feature a precision-cut Chamber, Gas Port and an 11-degree “Target” Crown. The .223 Wylde Chamber safely accepts both .223 Rem and 5.56x45mm NATO ammunition. In designing the R18 Mk2 Barrel, SAI took a page from Heckler & Koch’s playbook and gave the Chamber an Extended Root to limit flex and add strength. The Barrel is QPQ Nitride treated inside and out with the portion forward of the Gas Block Linear-Fluted to maintain rigidity while aiding in cooling and removing fore-end weight.


    SAI Combination Flash-Hider & Muzzle Brake:




    The Barrel is secured to the Upper Receiver by a somewhat unconventional “Sandwiching” system similar to that used by Daniel Defence for certain models such as the DD5 .308 rifle. The unique Barrel Nut features a Flange that is secured to a matching surface at the front of the Upper Receiver by 4 large bolts. The AR15-compatible Barrel Extension is “sandwiched” between the Barrel Nut’s flange and the front of the Upper Receiver. The four Barrel bolts are threaded into steel Heli-Coils embedded in the aluminum Upper Receiver so as to avoid stripping the threads. The Barrel attachment system is believed by the developers to enhance the overall accuracy potential of the rifle. We shall see about that. The other advantage of this particular Barrel mounting system is that AR-compatible barrels with a standard Rifle-length Gas Port are easily swappable by the home gunsmith. Install a heavier profile AR Barrel and you can create a “Precision” 5.56mm/.223 rifle right in your own hobby room.


    Barrel Nut and "Sandwiching" System:




    The Rifle-length Gas System consists of a short-stroke piston based directly upon the AR-180B design, with a .750 Gas Journal. The non-adjustable Gas Block is secured to the Barrel by 2 Allen (Hex) Screws on the underside. The Gas Block and Piston System are hidden from view and touch by an aluminum handguard with an interrupted 1913 Picatinny Top Rail and MLOC slots at the 3, 6 and 9 o’clock positions. The lightweight aluminum Handguard is currently affixed to the proprietary Barrel Nut by a series of four screws which must be removed in order to slide-off the Handguard and access the Gas System for maintenance. This shortcoming has already been identified by SAI and a QD Handguard design is already in development for the Mk3 version of the rifle, which I am told is on the drawing board. Removal of the Handguard is a simple matter and Alignment Tabs make re-installing the tube a simple matter. Just be careful not to cross-thread the screws in the Aluminum threads when replacing them.


    Barrel and Gas System:




    Moving back from the Trunnion area, we have an enhanced AR-180B-style Upper Receiver mated to a hybrid Lower Receiver with matched contours and that oh so familiar suite of AR-style controls. Indeed, seeing no need to reinvent the wheel, SAI adapted generic AR controls within the proprietary Lower Receiver such as the Bolt Catch, to work with the AR-180B-based Upper Receiver. Of course, not just any old Bolt Catch would do, so a custom Geissele “Maritime” style catch with extended pressure-pads was adopted for the Left side of the R18 Mk2 Lower Receiver. Another very welcome addition to the R18 Mk2 suite of controls is an integrated Bolt-Release on the Right side of the Lower Receiver. This feature allows the user to release the Bolt Carrier and Bolt forwards under spring pressure using only the Trigger Finger (rather than the Support Hand). Note that the R18 Mk2 Lower Receiver is not compatible with AR15 Upper Receivers, nor wil an R18 Upper Receiver mate to an AR15 Lower as the two rifles share no design commonality besides the use of some generic controls, parts and ergonomics.


    Upper and Lower Receiver - Left Side:




    The Lower Receiver features a nicely flared Magazine Well and an integrated Trigger Guard. It accepts generic AR Pistol Grips with a Beavertail and features a 1913 Picatinny Rail on the rear end for attaching a compatible Buttstock or an Accessory Plate. The Pistol Grip provided with the R18 is the Grey, rubber-coated Magpul MOE-K2+ with its comfortable, reduced grip-angle. The ambidextrous Selector Lever is the standard Sterling fare and those who own one of the earlier Sterling “safe queens” will immediately recognize it. The Selector activation is not overly stiff but has positive detents in the "Safe" and "Fire" positions. Although the Selector and Bolt-Release are ambidextrous, the Magazine Release is not. A Norgon-style Magazine Release would easily address that minor shortcoming for those who prefer a Magazine Catch on the Left Side of their rifle. The Magazine Release is adequately protected from accidental activation by the contours of the Lower Receiver. The rear-most pocket in the Lower Receiver is fitted with a Tensioning Screw which places pressure on the bottom of the Upper Receiver to effectivey remove slop between the two Receiver halves. This system is identical to that employed by Aero Precision for those familiar with those Receivers.


    Lower Receiver - Left Side:




    The stock trigger is 100% “Mil-Spec” AR15. It is single-stage, fairly smooth with a crisp, clean break at an average of 6.5 lbs pull. Reset is not too bad. You be the judge, but I exchanged the stock Trigger in my sample rifle for an adjustable Trigger Tech aftermarket unit. Night and day! The R18 Lower Receiver is specifically engineered to accept the Canadian Trigger Tech after-market, custom Trigger pack with user-adjustable Trigger pull-weight. Geissele Triggers ought to also work, along with most brands of after-market Trigger be they the cassette-type or the separate Hammer and Trigger set-up. With the R18 the maker and type of after-market Trigger is your call….


    Lower Receiver - Right Side:




    Turning to the Upper Receiver, the most notable feature is the Left-side, non-reciprocating Charging Handle very similar to that of the old-school FN FAL. The length of the sliding Charging Handle itself acts as a cover over the Cocking Slot, effectively sealing the rifle’s internals against ingress of foreign matter. The Right side of the Receiver mates closely with the side of the Bolt Carrier to also thwart the ingress of dirt and debris. The Mk3 version of the R18 will include the familiar AR-15 style of Ejection Port Cover. It will not be possible to retroactively fit the Dust Cover to the Mk2 Rifle, not that it is considered necessary in the first place. The Ejection Port Cover is expected to be on the Mk3 to satisfy potential LE clients who may insist on the additional safeguard against foreign matter. The steel Charging Handle operates smoothly and the aluminum Charger bar slides in a thick aluminum Receiver Rail which should result in nominal wear. The Cocking Handle is by necessity situated high up on the Left side of the Upper Receiver and some interference with certain optic mounts or rings may be unavoidable. SAI has attempted to mitigate this shortcoming with the use of an extended Cocking Handle which has the added advantage of providing additional purchase area for added leverage when extracting a sticky casing. As currently designed, the Cocking Handle does not double as a Forward Assist for silent chambering of a cartridge. The utility of a Forward Assist is debatable, however if the option exists to have one it would be a welcome addition. The non-reciprocating Cocking Handle is retained by a spring-loaded ball-bearing in the Cocking Knob mated to a detent in the Upper Receiver. The ball-bearing’s tension can be adjusted to compensate for any eventual wear to the Receiver Detent and the Detent itself could always be drilled deeper into the beefy Upper Receiver wall if eventually necessary.


    Cocking System:




    Purchasers of the R18 Mk2 will receive a rifle with a Fixed tubular Receiver Extension and a Gray Magpul CTR Buttstock. The Mk3 version expected will feature the Magpul Zhukov Folding Buttstock, which will also be backwards-compatible with the earlier Mk2 rifle. Both Buttstock options accept Cheek-Risers and come with QD Sling cup options. The Zhukov stock will allow the R18 to be fired with the stock folded a-la the 1980s, or with the Buttstock extended for maximum stability and accuracy. As far as the Mk2 is concerned, the non-folding Tubular Buttstock is extremely comfortable with a solid cheek-weld – just as you would expect from Magpul. Of course, with the Rear Picatinny Buttstock attachment system any Buttstock that is so equipped can be mounted. I have a “Safe Queen” SIG MCX which temporarily donated its Folding/Retractable Buttstock to the R18 Mk 2 just to see if it could be done and it was no problem.


    Buttstock Interface:




    The Picatinny attachment for the Buttstock means that in theory, the Stock height can be adjusted to suit the firer’s individual preferences. However, as currently manufactured the rear Picatinny Rail is quite short and adjustment from the center position will leave a portion of the Buttstock clamping system hanging over empty space. It is my belief that the Picatinny Rail should be extended one more increment upwards on the rear of the rifle so that additional adjustment can be made to put the Buttstock slightly over the line of the Barrel. This would serve to reduce any muzzle-flip as well as bringing the cheek-weld a bit higher and possibly more comfortable for certain optics users.


    Buttstock Interface 2:




    Users will want to note that the Buttstock’s Picatinny clamping system adds approximately 3.5 cm of non-collapsible length to the Receiver Extension. It is also worth noting that with the Picatinny system it is currently not possible to attach an unmodified A2-style solid stock. I have been told that SAI will have an adapter shortly for this. That also said, Midwest Industries in the States produce a variety of different stock styles with the same Picatinny interface, which is definitely the way of the future for attaching different Buttstock options.


    SIG MCX Buttstock Fitted to R18 Mk2 Picatinny Interface:




    Its various features notwithstanding, how does the R18 handle? The balance point is directly in front of the Magazine Well, which is ideal for weight distribution when carrying and shouldering the firearm. Equipped with Iron Sights alone, the R18 Mk2 feels very lightweight and “lively” in the hands. It is quick and thanks to the familiar ergonomics, comfortable and natural to point at a target. The head-height and cheek-weld are excellent for both Irons and Optics and can always be adjusted up or down slightly using the 1913 Picatinny rail on the rear of the Lower Receiver. The R18 weighs 3.6 kg or 7.9 lbs unloaded, “naked” from the factory. (By way of comparison, a WK180 is approx. 7.3 lbs)

    The Action is very smooth, which makes sense given that the Bolt-Carrier is riding on two polished steel rods inside the Upper Receiver. Each of the rods features an Operating Spring which combined provide ample forward force to strip a new cartridge and close the action at the end of the firing sequence. Standard AR-180 fare here folks, through and through. The Bolt is Nitrited Carpenter Steel and is (of course) Pressure and Magnetic Particle Inspected. Proof rounds are fired as part of the pre-shipment test-firing QC process.


    Bolt Carrier and Bolt:




    Stripping and reassembly of the R18 Mk2 are both simple and intuitive for anyone familiar with either the AR15 or one of the AR-180B designs currently on the market (The rifle does come with a downloadable manual). Simply push out the Rear Take-Down Pin and slightly depress the Rear Plate of the Recoil Assembly which will allow the Upper and Lower Receivers to pivot open and away from each other. If you wish to fully separate the Receivers simply push out the Front Take-Down Pin and the Upper and Lower will come apart. From there the Upper Receiver can be further stripped by racking the Cocking Handle and withdrawing the Bolt Carrier/Bolt/Guide Rod/Operating Spring Assembly from the Upper Receiver. From there, the Bolt Carrier and Bolt can be easily separated from the Guide Rods and Operating Springs by simply pulling. Removing the Bolt from the Carrier is a matter of pushing out the Firing Pin Retaining Pin from Right to Left on the Carrier, removing the spring-loaded Firing Pin from the rear of the Carrier, Removing the Cam from the Left side of the Carrier, and finally pulling the Bolt out of the front of the Carrier. Detailed stripping of the Bolt itself (eg. Extractor and Pin) is the same as any AR-pattern rifle.


    Field-Stripped R18 Mk2 (Note that the Factory Trigger has been replaced by my TriggerTech for Accuracy testing):




    Reassembly is simply done in the reverse order. Ensure 2 things as you proceed with reassembly:
    1. Depress the rear of the Firing Pin when re-inserting the Firing Pin Retaining Pin, and
    2. Make certain that the Operating Springs are fully seated within the Bolt Carrier by pushing the Carrier down along the Guide Rods (simulating the ejection cycle) until the Springs become visible in their holes at the front end of the Carrier.

    The Gas System need not be serviced every time the R18 Mk2 is Field-Stripped for maintenance, however it is also rather easily accomplished. Once you expose the Gas System by removing the previously mentioned four Handguard Screws and the Handguard itself, stripping the actual parts is a relatively simple matter. Pull downwards on the long Push Rod, compressing the Spring. This will create sufficient space near the front of the system to withdraw the central Spacer. Once the Spacer is removed, simply pull the Piston Cup down off of the Piston/Gas Block. Reassemble in the reverse order.


    Gas System Field-Stripped:




    A potential show-stopper for some will be the fact that the R18 Mk2’s Upper and Lower Receivers are fabricated from T6061 aluminum alloy, and not the harder T7075. I don’t have a dog in this fight and understand that there are pros and cons associated with the use of each material. At the end of the day, JR noted that T6061 is easier to cut and therefore requires less expensive machine time to fabricate each component. Added to that is his belief that the more ductile T6061 will withstand the explosive forces of a detonation out-of-battery better than the more brittle 7075-series counterpart. He may have a point there, not that anyone is anticipating breech explosions in the R18! In any case, the Sterling Arms International AR10 that I owned for a brief time was fabricated from T6061 as well, and there were no issues arising from use of the slightly softer alloy.


    Upper Receiver - Top View w/ 14" Handguard:




    The Finish on the R18 Mk2 is a combination of matte black Type III anodizing on the 6061 Aluminum and QPQ Nitride on the steel components with what appears to be Parkerizing on some small steel parts. I note that the anodizing does not appear
    to be all that thick/durable as both rifles received for testing had exposed aluminum on the sharp edges of the Brass Deflector after firing approximately 300 factory test rounds following assembly. Sterling’s Canadian Operations Manager related to me that there had been some difficulty in obtaining consistent anodizing colour from sub-contractors early in the production process, so it stands to reason that the anodizing system may still be tweaked as the R18 Mk2 enters full production.


    Lower Receiver - Top View (Note that my TriggerTech Trigger is installed for Accuracy Testing):




    Speaking of production rifles, a couple of minor issues have surfaced with the initial batch of 17 to come off the assembly line in Calgary thus far. In the first instance, the front face of the Bolt Carrier does not extend far enough forward to prevent
    the Extractor Retaining Pin from backing out, which can jam the Bolt in the forward position leading to a stoppage. This will be rectified by extending a small “raised collar” on the Bolt Carrier around the Bolt body, thus covering the Extractor Retaining Pin and preventing it from backing out. The second issue has to do with the length of the Rail within the Upper Receiver that controls the Bolt locking and unlocking process. The rail is slightly too short towards the rear of the Upper Receiver, which can make re-inserting the Bolt and Carrier into the rifle more difficult than it need be. Both of these minor fixes will be addressed as rolling changes going forward.

    So now the big question – how does the R18 Mk2k shoot? Tune in for Part 2 of my Review in a few days’ time after I’ve had a chance to hit the range….
    I have made a coom

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