HANDLING
The Mk3’s balance point is directly in front of the Magazine Well, which makes for ideal weight distribution when carrying and shouldering the new rifle. When equipped with “iron sights”, the Mk3 feels very lightweight and quite lively in the hands. It is quick to point and thanks to the familiar AR15-style ergonomics is comfortable and natural to point at a target. The cheek-weld and head-height are both excellent for both Irons and Optics and can be further adjusted up or down using the 3-slot Picatinny Rail on the Rear of the Lower Receiver.
The Mk3’s action slides very smoothly on two steel Guide Rods nestled within the top of the Upper Receiver. Each of the Rods “guides” an Operating Spring, the combined force of which closes the Bolt Carrier forward against the Barrel Trunnion with the rotating Bolt locked into the Barrel Extension. The curved Bolt Carrier body is guided during its back and forth movement by the matching curved Receiver Walls. The Bolt is hardened Stainless Steel with a single Ejector and a standard AR15 Extractor. The Rotating Bolt is controlled by an AR15-style hardened Stainless Steel Cam which follows a slot in the Bolt Carrier to lock and unlock the rifle’s action. Over-pressure Proof rounds are fired as part of the pre-shipping Quality Control checks and inspections.
Mk3 Bolt Carrier Assembly Riding Inside of Upper Receiver
FIELD STRIPPING AND REASSEMBLY
Very much like its Mk2 predecessor, the R18 Mk3 readily strips down for basic field maintenance without the use of tools. The exception to this is access to the Gas System beneath the Handguard, which requires a 5mm and a 2.5mm Hex Wrench to remove the bottom Bolt and a top Retaining Screw respectively. Field stripping is very intuitive and the rifle has been designed in such a way that the working components can only be assembled in the correct sequence and position. New or inexperienced owners are encouraged to refer to the Owner’s Manual (to be issued on-line) for specific instructions and the recommended sequence of stripping and reassembling the Mk 3.
The Mk3 Field-Stripped for Maintenance
Detail Strip of Captured Bolt Carrier Assembly
MAGAZINE COMPATABILITY
The following magazines were inserted into the Mk3 with an open Bolt to ensure proper fitment without over-travel. All magazines tested (less the ETS Gen2) dropped free when the Magazine Release was activated:
- Magpul PMag Gen 3 5/30
- Magpul PMag Gen 3 5/20
- Lancer AWM 5/30
- MFT "Pistol" 10/10
- ASC "Pistol" Mag 10/20
- ASC "Pistol" Mag 10/30
- Thermold CAF 5/30
- CAF Sterile/Generic Aluminum 5/30
- USGI Surefeed 5/30
- ETS Gen 2 5/30
- CZ Bren 2 5/30
- Surefire 5/60
RECOMMENDATIONS FOR FURTHER ENHANCEMENT
It is recommended that SAI make the R18Mk3 as ambidextrous as possible, thereby catering to Left-handed firers at no additional expense to the purchaser. This can be accomplished inexpensively and relatively easily by:
- Install a Norgon-style Ambidextrous Magazine Release
- Install a Right Side Selector Lever
In addition to the above, it is recommended that SAI consider the following based on initial customer feedback:
- Incorporate a Folding Charging Handle so that it lies flat against the rifle when folded.
- Offer the Folding Buttstock adapter demonstrated in the ADKAS "SAM" video "The SIG MCX we have ar home" on YouTube as a standard feature.
- Eliminate the small, Top Indexing Screw for the Handguard completely, but leave the Picatinny Indexing Tab. The screw is entirely superfluous and cannot be accessed when the rifle is fitted with magnified optics.
- Revise the Handgusrd Takedown Bolt so that it is "Tool-Less". See the HK Hanguard Takedown Bolt for inspiration, wherein they use a Bolt Locking Lug in a recess to turn the Takedown Bolt's Head.
- Reduce the diameter of the Barrel Nut to make it HK 416/MR223-compatible, including the Lockinig Bolt groove so that the Mk3 will accept HK Handguards as an option.
EXAMPLE BUILD
Below is an example of a utility build based on the R18 Mk3. The list of additions is detailed below:
- EoTech VUDU 1-10x Low-Power Variable Optic in American Defense "Recon" QD Cantilever Mount
- RiteOn Miniature Red Dot Sight on Offset Mount
- Midwest Industries Iron Sight Set
- Streamlight TLR-HL White Weapon Light
- Magpul Vertical Foregrip
- Magpul MOE Pistol Grip
- Strike Industries Ambidextrous Magazine Release
- BCM QD Slot for Sling Swivel
- B5 Systems SOPMOD Buttstock
- Magpul Windowed 5/30 Magazine with Ranger Plate
CONCLUSION
The R18 Mk3 represents a significant leap forward for the design as well as the methods of manufacturing, assembling and inspecting the Sterling Arms International rifles prior to sale. The use of upgraded T7075 aluminum alloy, Stainless Steel for selected parts, and a Melonite-lined Chamber and Bore are all major advancements in the durability and longevity of the system, further enhancing the rifle’s value. With the latest enhancements and redesigns, the R18 Mk3 arguably represents not only the most advanced Canadian-manufactured Short-Stroke Piston rifle design currently on the market, but also the most cost-effective in terms of value for dollar. With the 33% reduction in MSRP from $2700 CAD to just $1800 CAD (initially), the Mk 3 also clearly provides the greatest value for the buyer’s precious dollar. My initial impressions based on handling the Mk3 and carefully examining the rifle’s component parts are highly favourable. Provided the new rifle delivers acceptable accuracy together with respectable reliability and reasonable durability, I believe that SAI has a serious contender with a winning combination of quality and affordable price on its hands. I predict a high degree of popularity for the R18 Mk3, as the principal competition for the Internal-Piston design of the Lockhart “Silver” Raven within the Canadian modern utility and sporting rifle market.
Part 2 - Shooting Impressions and Accuracy Results. Stay tuned for Part 2 of my Review once I get a chance to hit the range a few times for some accuracy and reliability testing. The Test Rifle that I have for the Part 1 Review cannot be fired due to a prototyping tolerance issue. That should be resolved within two weeks, with live-fire testing commencing shortly afterwards. Expect approximately 3 weeks (give or take) between Part 1 and Part 2 – Shooting Impressions and Accuracy Results.