Gun of the Week: Primary Weapons Systems UXR

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posted on April 17, 2026
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For the modern firearm enthusiast, one of the key elements of new firearm design is modularity. From stocks to barrels to accessorization, it seems that everyone wants the ability to tailor their firearm to their personal needs and preferences. Primary Weapons Systems took that demand and created an answer that takes modular firearm design to the next level with its UXR or User Xchangeable Rifle.

"What's really neat about this rifle is it is modular. And it's not just modular like an AR-15 or an AR-10 where you can separate the upper and lower and change calibers among cartridge sizes. This swaps everything," American Rifleman Executive Editor Jay Grazio said. "You can swap out the barrel. You can swap out the magazine well. You can change it from a .308 to a 5.56. They're going to have 6.5 Creedmoor, 6 mm ARC down the road. They've got .300 Blackout in addition to the 5.56 NATO. All of these go into one rifle."

The Xchange conversion involves changing the barrel (held in place by three clamping screws), the piston rod, the bolt and the magazine well, if necessary. The rifle uses a universal recoil spring and bolt carrier. Parts for a specific cartridge are coordinated and clearly marked with a dot system. Conversion kits cost $600, plus $150 for the appropriate magazine well.

"If you are limited on space, if you're traveling, it's a super, super slick idea," Grazio said. "You loosen a few bolts, you take the barrel out and handguard. This whole top rail is all one piece. So if you put on a scope and you have a clip-on, it's rock-solid. If you put on iron sights, again, very solid set-up. You've got a side-folding stock, so it folds down for transport. It's very customizable to the individual shooter."

The human interface of the UXR is well thought-out and intuitive. Controls are fully ambidextrous, with a safety lever, magazine release and bolt release mirrored on each side of the rifle. All three can be reached without shifting the firing grip. The non-reciprocating charging handle is mounted forward, folding when not in use, and can be switched to either side without tools. Despite housing a gas-piston system, the handguard is slim and easy to grip, and it narrows at the forward end to provide space for a thumb over “C-clamp” hold.

"It does take a standard AR-15 style pistol grip. This particular model is in .308. And as you can see, we've got a standard Magpul SR-25 PMAG," Grazio said. "There's M-Lok slots up front if you want to add lights or accessories. Standard muzzle brake. You can obviously put on a suppressor, if you'd like."

For more information on the Primary Weapons Systems UXR, read our full review here, and you can visit the Primary Weapons Systems website here.

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