Build of the Month

Build of the Month: Radian Bay

By Joe Kriz


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When we started our Build of the Month features, we set out to put together complete firearms using guns and gear we had stuffed in our safe and lying around the office. However, none have been “builds” in the true sense of the word – until now.

Starting with a Radian Model Builder Kit, we pieced together a rifle from the inside out that has quickly become one of our favorites. Inspired by its two-tone brown receiver and handguard with black furniture and Swampfox Warhorse LPVO, we’ve taken to calling it the Radian Bay – named after horses with a brown body and black shading across their mane, legs, and tail.

Saddle up for our April 2024 Build of the Month.



Radian Model 1 Builder Kit

At the core of the build is a Raidan Model 1 Builder Kit. Built to order, the Model 1 consists of a Radian AX556 Lower Receiver, billet upper receiver, M-LOK handguard, and just about every pin and part you need except a bolt, barrel, and trigger. With five handguard lengths and five receiver/handguard colors to choose from, we opted for the 15.5” variant in Radian Brown.

Already familiar with the superior quality of Radian Weapons, we knew we were starting with a solid foundation. The included Raptor-SD Charging Handle and ambidextrous safety selector, bolt catch, and magazine release only added to its form.

Roscoe Bloodline Barrel

Filling in the handguard, we selected a 16” M4 5.56 NATO Bloodline Barrel from Roscoe Manufacturing. Designed around United States Army Special Operations Command specs, the 4150 CMV and nitrided barrel takes advantage of a mid-length gas system for smooth operation and efficient dwell times while coming under 29 oz.

Threaded 1/2-28, we mounted a Dead Air KeyMo Flash Hider to tame this Bay’s neigh and allow for future suppressor use.

HIPERFIRE Enhanced Duty Trigger

Driving the rifle is a HIPERFIRE EDT Designated Marksman Trigger. Not quite curved and not quite flat, the Designated Marksman trigger sports a two-position design with its Duplex Trigger Bow allowing for both a high and short pull and a tactical precision, long trigger pull. The trigger breaks crisp and clean with short over travel and a positive reset for consistent shots on target you can feel and hear.

B5 Systems Furniture

To complete the rifle interface, we added black furniture from B5 Systems. The Bravo Stock is simple but effective, with a lightweight design featuring an ergonomic cheek weld, cushioned buttpad, and QD sling mount we’ll make use of later. Further up, the Type 23 P-Grip makes use of an enhanced vertical grip angle and aggressive texturing to put the shooter’s hand in a more control-friendly position without losing positive purchase when galloping and gunning.



Swampfox Warhorse 1-6x

Horses use binocular-like vision when looking forward, so it’s fitting this build was topped with a variable magnification optic like our first focal plane (FFP) Warhorse 1-6x.

Built on a 34mm tube with 24mm objective lens, Warhorse combines speed and precision in a compact design for close-quarters engagements and long-range shooting. High-quality glass and fully-multi coated lenses further ensure exceptional light transmission and glass clarity while a push/pull locking elevation turret with zero reset and capped windage protect adjustments from bumps and bucks.

Available with our Dragoon reticle featuring a red or green illuminated 1.2 MOA center dot and 26 MOA horseshoe with MOA or MIL ranging, we selected the MIL version in red to simplify our math on the range.

Zero Gravity Summit Mount

While we normally like to use Swampfox mounts for our builds, we recently got a Zero Gravity Summit cantilever mount in and wanted to give it a try. Though not completely skeletonized, the mount weighs in just over 5.6 oz. – only half an ounce heavier than our Freedom Mount.

However, instead of removable top rings, the Summit utilizes an innovative clamp design with double hinges that wrap around the scope body and come together at the top with two screws. This prevents scope pinching that can leave ring marks with excessive torque. Machined from 7075 T-651 aluminum, we chose our preferred 1.93” centerline height.

For backup irons, we quickly threw on a Magpul MBUS Pro Front Sight and USMC-stamped Knights Armament Folding Micro Rear Sight that sits nicely under the Warhorse ocular assembly.



SureFire M640DF-PRO

You can’t shoot what you can’t see – and if you’re a horse, your vision in the dark isn’t very good. All the more reason to add a weapon light to the Radian Bay in the form of the SureFire M640DF-PRO Turbo Scout Light.

Combining the best attributes of the standard M640 Scout Light Pro with 10,000 candela-700 lumen performance and dual-fuel capability, the M640DF-PRO delivers a far-reaching beam with the longest runtime of any SureFire long-gun weapon light. Paired with a SureFire WeaponLight Switch and mounted to an inline Arisaka mount, operating the light is easy with a C-clamp grip.


Emissary Development Handbrake

Like reins on a horse, having an under-rail forward grip can help shooters achieve better control of the rifle by pulling it tighter into their body. We achieved this with the addition of the Emissary Development Handbrake. Its forward-swept angle fit our grip perfectly and provided the support we needed to ride.

Flatline Fiber Rifle Sling

No battle rifle should be without a sling, and Georgia-based Flatline Fiber Co. makes one of our favorites. Their Standard Rifle Sling is constructed from durable 1” nylon webbing with quick-adjust pull tab for a slim, minimalistic, and functional look and feel. We attached it to the B5 Bravo Stock and Radian handguard using integrated and M-LOK QD mounts, respectively.

For storage, we like to wrap a Grayfighter SRC-3 retention strap around the sling to keep it tucked away while remaining quick to deploy.



Anyone who has built a rifle from the ground up knows the excitement of seeing the parts come together to form a functional firearm. The Radian Model 1 Builder Kit provided the perfect platform to start, getting us 75-percent of the way with unmatched fit and finish.

Each additional component we added, from the Roscoe barrel to the B5 Systems furniture, got us closer to the range. The Swampfox Warhorse 1-6x LPVO offers versatility to match the 5.56 rifle’s capability and the SureFire weapon light setup physically balances the build while contributing to the two-tone brown and black look we love.

More than just another rifle in our stable, the Radian Bay build is one we intend to break in and shoot regularly. It may even become our next thoroughbred.



Radian Model 1 Builder Kit, 15.5” Handguard, Radian Brown

Rosco Mfg. Bloodline M4 5.56 NATO Barrel, 16”

Dead Air Silencers KeyMo Flash Hider, 1/2-28

HIPERFIRE Enhanced Duty Trigger Designated Marksman

B5 Systems Bravo Stock

B5 Systems P-Grip 23, Black

Swampfox Optics Warhorse 1-6x FFP LPVO, Dragoon MIL, Red

Zero Gravity Summit Mount, 34mm, 1.93”

Magpul MBUS Pro Front Sight

Knights Armament Company Folding Micro Rear Sight, 200-600m

SureFire M640DF-PRO Turbo Scout Light Pro WeaponLight

SureFire SR07 WeaponLight Switch

Arisaka Inline Scout Pro Mount, M-LOK

Emissary Development Handbrake, M-LOK, Black

Flatline Fiber Co. Rifle Sling, Coyote

Greyfighter Gear SRC-3 Retention Strap, FDE

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