Self Defense

Primary Weapons Systems UXR

By: Dave Bahde

The most promising modular multi-caliber rifle to date

The idea of a “convertible” battle rifle or carbine is not new, with the concept going back at least 25 years. While there are multiple carbines with interchangeable or quick-change barrels, they are limited to an overall length cartridge that will fit in a STANAG (AR) magazine. Light versions are typically based on the 5.56mm cartridge, and heavy models are 7.62mm. Each can be changed to calibers using what amounts to the same size magazine and a similar size bolt face. For instance, 5.56mm can accommodate 6.8 SPC, .224 Valkyrie, 6mm ARC, 300 BLK, etc. Heavy calibers may include .308, 6.5 Creedmoor, 260 Rem, etc. Convertible rifles will accommodate all of those in the same basic rifle platform. While popular in some circles, these platforms have remained limited due to cost and interest.

There are several bolt guns that will accommodate anything from 5.56mm to 338 Lapua, but semi-autos are rare. Rumors spread about a convertible FN SCAR model twenty-plus years ago, but it never materialized. Colt’s Model 901 arrived in 2012, and my test rifle worked great in both .308 and 5.56mm, but it just never caught on, and production stopped. Desert Tech’s bullpup version is the only commercially successful example of a convertible platform. Their latest model works great, but it’s a bullpup, and America is less than enamored as a whole with that design. No one has introduced a more conventional design (AR-like) that worked until now — the new Primary Weapons Systems UXR.

Up front you’ll find the quick-change XChange barrel system and M-LOK handguard. The PWS piston-drive mechanism uses a three-position gas block for suppressed, normal, and adverse conditions, and a unique expansion chamber built into the barrel helps direct residual gas out the front instead of back at the shooter. The factory PWS FRC compensator prioritizes recoil reduction but also excels at flash reduction.

Primary Weapons Systems UXR

So, who exactly wants a single rifle that can be converted to either a .308 (or similar) or 5.56mm without much fuss? Competitors have enjoyed the flexibility when it comes to bolt guns; using the same sighting system and controls makes for an easy conversion. Commercially, they have been kind of hit-and-miss, but if you are looking at military and police use, there is some real value. Benefits here include one single platform, similar or identical parts, the same ergonomics, the same manual of arms, etc. Need to change assignments or missions? Just configure as necessary.

Like the SCAR and a few others, the upper receiver is the serialized component. Also like a SCAR, charging the UXR is done via a folding forward handle that’s non-reciprocating and easily swapped from side to side. The handguard — part of the UXR XChange system — is interchangeable for different lengths. The handguard is slim but taller, given it covers the piston system. The gas system is labeled a long stroke, but it is more like a “longer short stroke” because the piston is not attached to the bolt. A three-position rocker valve allows gas adjustments for suppressed, normal, and adverse conditions. The barrel, which is the heart of the XChange system, is nestled into a titanium trunnion for strength and light weight. An “evacuation chamber” on the barrel reduces pressure, resulting in a softer recoil impulse as well as less gas in the shooter’s face. Currently, UXR barrels are available in .223 Wylde (will chamber .223 Rem. and 5.56x45mm NATO), 300 BLK, and .308 Win — all in 16-inch variants (currently). The modularity of the UXR is about as good as it gets, and the rifle can be easily broken down and reconfigured without the need for any armorer’s tools. Two push pins and loosening the barrel fixture screws with a 1/8” Allen key are all that’s required to completely break down the UXR, which can easily be accomplished in less time than it takes to load a muzzleloader. Primary Weapons put a ton of engineering into the UXR, and it shows. They took the best aspects of the top players in this segment and melded them into a very versatile, very modular rifle.

The UXR uses a modified short-stroke piston system with a stainless-steel bolt-carrier group that rides on precision-cut rails. The recoil spring is contained within the upper receiver, allowing for a folding buttstock

Primary Weapons designed the UXR to encompass most, if not all, of the most popular characteristics consumers want. Prime examples of this are fully ambidextrous AR controls, an AR trigger, and an AR handgrip. The bolt release — sitting just forward of the trigger guard — is also ambi, but you push down to release, and it can be used to hold the bolt open. The lower receiver is polymer and encloses a metal housing that secures the trigger. The magwell, which is also part of the UXR XChange system, is polymer and interchangeable for different magazine sizes; outwardly sized to an AR10/SR25 magazine, the 5.56/300 BLK sized magwell is filled in internally to fit STANAG magazines. The stock can be configured to fold to either side, is made of aluminum, adjusts for LOP and cheek height, can be switched to fold on either side, and attaches to the receiver via a Picatinny rail section. The fact that the lower receiver is not the serialized part makes it easily interchangeable without the need for ATF paperwork.

UXR controls are 100 percent ambidextrous, including the safety selector with its short 50-degree throw, magazine release, bolt release/hold open, and non-reciprocating charging handle that can easily be swapped side-to-side. PWS outfits the UXR with an excellent single-stage 2.5 to 5-pound adjustable TriggerTech trigger.

Testing

My .223 Wylde chambered test rifle was equipped with the 16-inch barrel, which, as of writing this article, was the only option available. While PWS lists several caliber conversion kits, all were out of stock online, leading me to assume they’re still getting up and running with some components. The factory muzzle brake accepts the “Plan B HUB adapter” or Atlas system, so I picked up an adapter for my Dead Air Silencers (www.deadairsilencers.com) Nomad Ti to use during testing. The Nomad Ti is so light you barely notice it’s there and does not affect rifle handling outside of the added length.

The riflescope used for testing was a Trijicon (www.trijicon.com) VCOG 1-8 power. These scopes are built like small tanks, with glass that is incredibly clear and bright. The reticle is a lighted segmented circle TMR mounted in the first focal plane.

The UXR’s rugged aluminum buttstock can be configured to fold to either side, has six length-of-pull positions, and an adjustable comb height. Ambi QD sling swivel cups can be found at the rear of the buttstock as well as the rear of the receiver.

Range Time

Primary Weapons issues a “sub-MOA guarantee” for “every rifle / every upper,” and the UXR met this promise with the majority of testing ammo. My best five-shot group at 100 yards came with Federal’s 69-grain Gold Medal Match measuring 0.75 inches. The rifle also liked the Black Hills 69-grain TMK load, with a group size measuring nearly the same. All of the 77-grain rounds were very accurate. Most average groups were around an inch, other than the sole 55 grain, which was closer to 1.5”. This rifle clearly prefers heavier bullets.

Shooting it out to 500 meters provided consistent performance, especially with the Black Hills 77 grain load, which is consistently the most accurate 5.56mm round I’ve used. Moving between steel at 100, 200, 300, and 500 meters, it was essentially point-and-shoot with the heavier grain weight loads. The UXR is soft shooting with their FRC brake, so much so that I bought one for one of my other rifles. Suppressed, it was even softer and didn’t produce a ton of excess gas in the suppressed setting. It also worked fine shooting suppressed in the normal setting, albeit a little harsh. A really nice surprise was the almost complete lack of impact shift between running the rifle suppressed and unsuppressed. Shift was nonexistent at 50 meters, negligible at 100, and unnoticeable at 300 meters. I was able to complete pass after pass at those distances with and without the suppressor using the same holds on the 12-inch square steel.

Changing UXR calibers is extremely quick and easy, and PWS has made it affordable to do so with their caliber conversion kits. Currently listed calibers are .223 Wylde, 300 BLK, and 308 Win., with many more options in the works. Streamlining things, the upper is the serialized part, meaning all XChange components can be shipped directly to your door.

Thoughts

It’s important to remember this is really a small .308 rifle that can be converted to 5.56mm, much like most every “convertible” rifle out there (bolt or auto). The receiver is a tad longer by necessity, and there is no real way to get around the overall length other than to use a short barrel.

Another byproduct of design is that, at 7.90 pounds, it’s on the heavy side for a 5.56mm. That is about right, maybe even light for most 308s, but still heavier than your typical 5.56mm AR. Very high-quality AR15s are coming in a solid pound lighter, but that’s the price you pay for the high level of modularity you get with the UXR. That being said, the weight contributes to its soft shooting. The Primary Weapons Systems gas systems in their line of ARs run cooler as a rule, cleaner in most cases, and tend to be some of the softest shooting carbines out there. The UXR is no exception and may even be better.

The UXR met its sub-MOA guarantee with four of the five loads tested. The tightest five-shot/100-yard group, shown here, measured 0.75 inches and was printed with Federal 69-grain Gold Medal Match.

A rifle of this quality, with this level of modularity and convertibility, is not going to be cheap, but it’s not overly expensive either. Retail on the rifle is $2650.00, with barrel/piston mechanism kits coming in at a surprisingly affordable $575.00 each. Magwell’s are also on the inexpensive side at $129.95. The only other carbine out there that can do this is about the same price but with more costly conversion kits, and there are a couple of interchangeable barrel systems with significantly higher price tags, making the UXR reasonable for what you get.

The author took the UXR all the way out to 500 meters with excellent results. As a nice surprise, there was nearly zero impact shift between running the rifle suppressed and unsuppressed at distance.

Bottom Line

It would have been nice to test this with a .308 barrel as well, given its real stand-out difference is that it can be converted back and forth from small caliber to large. So, for now, it’s a really nice 5.56mm rifle with what appears to be a bright future as a rifle you’ll be able to convert to a bunch of other calibers. Maybe a follow-up review will be in order at some point. For now, this is the best multi-caliber platform I have seen in well over 20 years. Not for everyone, for sure, but for those like me who enjoy the versatility, the UXR is a really good example of a truly convertible rifle. See the UXR at your nearest dealer, or for more information, contact Primary Weapons Systems; Tel.: (207) 344-5217; E-mail: [email protected]; Web: www.primaryweapons.com.