Upgrade Your Common AR Into A Varmint Powerhouse

Converting a standard AR-15 into a purpose-built varmint rifle can be a worthy exercise for those interested. It’s an advantageous process for rifle shooters seeking enhanced accuracy and extended range. Not to mention, converting an AR also means ending up with a semi-automatic platform tailored to the precise demands of small-game and predator hunting. 

While AR-15s are renowned for their modularity, optimizing them for varmint applications requires upgrading key components. The most critical upgrade is the barrel, but the optic, trigger, and stock play an important role in ensuring tighter groups and long-distance consistency.

After two decades of experience in the construction industry, I’ve learned that every successful project starts with a solid foundation. That same principle guided my approach to this build.

To kick off my project, I took a black-anodized Bear Creek Arsenal BC-15 multi-Caliber forged complete lower receiver and paired it with a right-side charging upper receiver. This gun comes with a heavy-contour .223 Wylde 18-inch parkerized barrel with a 1:8 twist rate from the factory. To cycle the action, Bear Creek added mid-length gas system that offers a balance of durability, accuracy and a pleasant recoil impulse.

Completing this AR-15 Varmint build is not about aesthetics or name recognition. Instead, I focused on selecting components with proven performance and reliable craftsmanship. Bear Creek Arsenal’s reputation for precision machining and affordability made it a practical foundation for a dedicated varmint rifle. Drawing a parallel to construction once more, careful planning, quality materials and skilled assembly yield dependable results. My AR-15 Varmint rifle was assembled with that philosophy in mind.

Varmint Friendly Stock & Grip Upgrades

Considering the relationship between a rifle and the way its stock supports accurate shooting, furniture upgrades for varmint-ready AR-15s are necessary for achieving the precision required in small-game and long-range shooting.

I used Magpul components to achieve this goal. Starting at the rear, I replaced the factory stock with the Magpul PRS Lite. This stock offers a range of adjustments, including comb height, length of pull, butt pad height and cant to allow for a highly personalized fit. PRS Lite stocks can easily be adjusted with simple Allen wrenches. Likewise, the PRS Lite’s enhanced design contributes to stable shooting whether from a bench, prone position or tripod. Its lightweight polymer construction keeps the rifle well-balanced, while the wider rubber butt-pad helps buffer out recoil. 

I replaced my rifle’s factory grip with a Magpul MOE-K2, an aftermarket AR-15 that provides a more vertical grip angle. Its angle is better suited for precise shooting from supported stances. Its unique Magpul TSP textured surface enhances grip security in challenging conditions. Like many other Magpul AR-15 grips, the MOE-K2  includes a practical built-in storage compartment that offers convenient space for small tools or batteries.

Varminting Trigger 

Upgrading the trigger on an AR-15 can have a highly rewarding impact on overall performance. My rifle received Rise Armament’s Iconic Independent Two-Stage Trigger. Its unique two-stage design stands out because both stages are independent with separate mechanical components. It definitely isn’t the norm in other two-stage triggers.

The Rise Armament’s drop-in design made it quite easy to install. Once in place, I noticed a consistent trigger pull of just over 3-pounds with almost no creep. This made it easier to take quick, predictable shots and improve my follow-up speed. Overall, this trigger upgrade gave me more confidence. Even my shot groups reflected this as I managed to print tighter groups. Upgrading the trigger wasn’t just a part-for-part upgrade, it altered  the rifle’s overall performance. Ultimately this meant having a level of control closer to what I’d expect from a custom setup.

AR-15 Varmint Barrel Upgrade

Barrel selection is a critical factor in optimizing the external ballistics and thermal stability, especially for an AR-15 set up for varmint. With that in mind, I replaced the factory 18-inch Bear Creek Arsenal parkerized heavy barrel with a 22-inch Tactical Kinetics FM Varmint Special unit. This barrel is manufactured from stainless steel and also has a heavy-contour with a 1:8 twist rate and threaded muzzle. It cycles the action with a longer rifle-length gas system.

The four inch increase in barrel length provides additional bore travel time for expanding propellant gases. It means I get a 100–200 feet-per-second muzzle velocity boost, depending on ammunition. It also means I get a flatter trajectory and reduced time of flight– are advantageous when engaging small targets at extended distances. Its 1:8 twist rate can stabilize both lighter and heavier weight projectiles. This makes my rifle especially useful for adapting to variable wind conditions or longer-range applications.

Finally, the stainless steel material enhances bore smoothness and corrosion resistance, while the heavy contour profile minimizes harmonic distortion (barrel whip) and promotes more uniform thermal expansion. These characteristics collectively support greater shot-to-shot consistency during extended firing strings.

I installed the new barrel in approximately 30 minutes by simply using an upper receiver vise block. I simply removed the handguard and barrel nut prior to taking out the factory barrel. Then I seated my new barrel into the upper receiver extension, aligned it and torqued it to the correct manufacturer specifications. I installed a new gas block and rifle-length gas tube. After verifying gas system alignment and pining the block, I replaced the handguard.

Crowning The Muzzle

There are plenty of barrel accessories out there, and choosing the right one depends on the needs of your build. In my case, I added a Kahntrol HexMod CWES muzzle brake. I found that it offered the balance I was after in my AR-15 Varmint build.

Like the barrel itself, installing this muzzle device was also straightforward. After securing the upper receiver assembly in a vise with a receiver block, I removed the original flash hider by backing it off counterclockwise (after taking off the crush washer). 

After cleaning the muzzle threads properly,, I mounted the HexMod brake using a new crush washer to time it properly.

The HexMod’s design uses hexagonal ports to redirect gas both outward and rearward, which noticeably cuts down on recoil and muzzle rise. Even though 5.56 mm cartridges don’t kick much, the difference is clear. Follow-up shots are faster and staying on target feels easier. Again two perks that really pay off in Varmint hunting scenarios or fast-paced shooting.

It doesn’t hurt that the Kahntrol brake feels solid and durable either. Besides its sturdy design, it includes a corrosion-resistant finish that should hold up well over time. If control and consistency matter in your build, this upgrade delivers where it counts without overcomplicating things.

Topping The Varmint AR-15 Off With Capable Glass

When it comes to varmint rifles, choosing the right optic is just as important as selecting the barrel, trigger or stock. A riflescope’s glass and its available magnification makes a big difference in how confidently you can engage distant targets. For my AR-15 Varmint build, I went with the Athlon Argos BTR GEN 3 10-40×56 scope, paired with the Athlon Armor Cantilever 30mm mount with 20 MOA built-in elevation.

I chose this combo due to the high magnification, solid tracking and overall rugged construction–all features that come into play when you’re trying to land precise shots on small targets at longer ranges. The 10-40x zoom range and large 56mm objective lens provide excellent clarity. I especially noticed the difference in early morning and late evening light, where visibility and a scope’s light-gathering ability can make or break a shot.

The BTR GEN 3’s second focal plane MOA reticle is well-suited for varmint shooting. This reticle features fine lines and floating center dot that a clean aiming point. I also really like this scope’s turrets because they give off a clear, tactile click that makes on-the-fly adjustments feel solid and consistent. These turrets also include a slick zero-stop system that quickly lets me return to zero after dialing for elevation. The BTR GEN 3 weighs a little over 2 pounds, which isn’t exactly lightweight, but that hasn’t been an issue with my benchrest-style or bipod-supported setup. In fact, my AR-15 Varmint rifle build’s overall added stability more than makes up for the heft.

Aim Small, Miss Small

Range time is a crucial step with any new rifle build. Once everything was mounted, zeroed and adjusted in place it was time to evaluate performance. I tested three widely available varmint loads: Black Hills Factory New 50-grain V-MAX, Fiocchi Field Dynamics 55-grain Polymer Tip, and Hornady Superformance Varmint 53-grain V-MAX. 

Early in the session, I noticed the need for a slight adjustment to the gas block to improve cycling. Once dialed in, the rifle ran flawlessly. I fired five sets of five-shot groups, allowing the barrel to cool between each to monitor consistency. 

I also ran a couple of ten-shot velocity strings to record extreme spread and standard deviation. The Black Hills and Fiocchi rounds produced decently tight groups. I was beyond pleased with the rifle’s performance and how the build came together.

Final Bullet Points

Transforming a basic AR-15 into a precision varmint rifle requires more than cosmetic changes; it’s about thoughtfully selecting and integrating components that elevate accuracy, comfort and consistency. Upgrading to a precision barrel significantly tightens groups. Installing a match-grade trigger ensures cleaner, more predictable shots. Swapping the factory stock for an adjustable precision stock and replacing the standard grip with one designed for comfort and control further stabilizes the shooting platform. Finally, adding carefully chosen accessories such as a quality optic and bipod rounds out the build, tailoring the rifle to the unique demands of varmint hunting. All of these upgrades in tandem transform the AR-15 from a versatile general-purpose carbine into a competent precision tool ready to deliver reliable performance in the field.

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