The M4 carbine owes its versatility largely to its collapsible stock making the rifle handier and lighter than standard issue. However, the regular collapsible stock may not be as rigid or user-friendly as a fixed buttstock, but the Magpul UBR (Utility Battle Rifle) adjustable buttstock compared to typical collapsing stocks, offers the stability of a fixed A2 type of stock, with consistent cheek weld in any position. The cheek piece is also repositionable, but it would provide the same piece of smooth, beard-friendly material every time to shooters skin.
Featuring seven-position length-of-pull (LOP) adjustment with five positions integral preset system and robust lock mechanism the UBR provides very solid support in the shoulder. Though it is constructed of glass-fiber reinforced polymer, at approximately 1.41 lbs., the weight of this stock is on the heavier side, exceeding in mass most of the rival telescoping buttstocks. Due to significant mass, the Magpul UBR provides extra counterbalance weight to improve handling on the 18-inch barrel as well as weapons with muzzle-heavy accessories or bull barrels.
As one of the strongest adjustable stocks on the market, the length of the UBR stock retracted is around 7.75″ and 11″ when fully extended, making it comfortably for using by operators of different size and equipment (body armors, and so forth). Additionally, at the central area, the UBR stock also has a small compartment that may fit a bolt, a bore snake, ear-plugs or any other small accessories that could be handy.
The robust, multi-shell construction stock that can withstand to even the largest calibers found in AR-platforms has a sleek design that is aesthetically pleasing. The UBR package includes the proprietary Entry-Length Receiver Extension tube, but the customer has to buy an M4 carbine spring and buffer separately. This hybrid adjustable and very appealing precision style rifle stock belongs to upper price range, but it is understandable as Magpul UBR offers numerous ways to customize the stock and accommodate it to everybody.