In 2003, Arne Boberg, founder of Boberg Arms, began work on an unusual cartridge feeding system in the comfort of his own basement. His goal was to redesign the pocket pistol platform so that it could be powerful and reliable with a manageable level of recoil. In 2013, the company released the XR9-S sub-compact 9 mm pistol. In 2014, the XR line grew with the addition of the XR45-S chambered in .45 ACP.
One of the characteristics of the XR45-S that immediately caught my attention was its relatively short 5.77” slide assembly. Next to another top-notch compact .45 ACP, the Glock single-stack G36, the XR was a full inch shorter in overall length. But when the slides were removed and the barrels lined up side-by-side, they looked to be the same length (the G36 barrel is actually 3.78” long, making it 0.03" longer than the XR barrel).
How is it possible to fit this much barrel into an abbreviated slide? Boberg did it by changing how the ammunition feeds into the chamber. The typical modern semi-automatic uses a box magazine fitted into the grip frame which positions the cartridges with the nose of the bullets tilted slightly upward. When the pistol is fired, a portion of the energy expended by the cartridge is used to move the slide backward toward the shooter. This motion opens the action and compresses the spring(s) of the recoil assembly. As the slide reaches the end of its reverse journey, the energy stored in the recoil assembly forces the slide to move forward, pressing a fresh cartridge from the magazine forward against a feeding ramp and into the chamber.
The XR series of pistols still use a removable magazine fitted into the grip but the ammunition feeds from the magazine in reverse (much like the massive Mars Automatic Pistol that went out of production in 1907). Cartridges rest in the magazine nose down with the cartridge base tilted up. As the slide moves backwards, a pair of spring loaded extractors grip and pull the cartridges backward out of the magazine onto a lifter. When slide moves forward the cartridge is pressed directly into the chamber, so no feed ramp is required.
This reverse-feed system is paired with a rotating barrel, locked-breech type action. The barrel, bolt face and slide stay firmly locked together until after the bullet has left the barrel. The barrel and slide then move backward in tandem for the first 0.125" of the cycle. The barrel then rotates 23 degrees counter-clockwise before unlocking from the slide which then continues to move rearward on its own. The result is a barrel that remains pointed directly forward instead of tilting upward like the barrels of traditional short-action pistols.
The Boberg XR design provides several noteworthy advantages. The barrel's chamber rests above the magazine well instead of in front of it. This provides the space needed to fit a longer barrel inside of shorter slide. The rotation of the barrel acts like a brake to slow the rearward movement of the slide, reducing felt recoil. Because a heavy recoil spring is not required, the slide is easier to cycle manually.
The XR45-S pistol tested for this review is the Standard two-tone version. The beveled slide is constructed of satin finished stainless steel with angled slide serrations at the rear. The barrel, barrel block, external extractor, external hammer and trigger are also stainless steel. To help reduce the pistol's weight, the frame is made of aircraft-grade aluminum with an oval trigger guard and a matte black hard-anodized finish. The two removable textured polymer grip panels are each held in place by a pair of small hex head screws.
The metallic low-profile 3-dot sight system features dovetailed front and rear sights that are both adjustable for windage. A passive firing pin safety prevents the gun from going off if dropped. The thin full-length guide rod, fitted with a single recoil spring, rests to the left of the barrel instead of underneath it. It can be seen protruding from a small hole in the slide when the action is open.
The double-action-only trigger cycles a flat, plate-like exposed hammer. Some double-action-only pistols have heavy triggers as a safety feature, sometimes as heavy as 10 to 12 lbs. Glock offers its safe-action pistols with a typical trigger pull of 5.5 lbs. The XR45-S trigger split the difference at 8 lbs. 4-oz. of trigger pull. The trigger's travel is a little longer than some but it's so smooth that it feels lighter than the trigger gauge indicates.
The remaining external controls consist of a takedown lever and a small round button magazine release, both of which are mounted on the left side of the frame. The slide does not lock open automatically when a last shot is fired or with an empty magazine in the grip. The takedown lever can be used to hold the slide open when rotated 80 degrees while the slide is pulled all the way back. The magazine button is small and must be pressed and held down while the magazines are manually removed from the grip. The 6-round rear-feeding magazines have been simplified to just three components. These include a stainless steel body, a spring, and a polymer base plate. There is no follower and the base plate is held in place by the spring instead of an insert.
Despite its unconventional configuration, the XR45-S is easy to field strip for cleaning. After removing the magazine and verifying the chamber is empty, pull the slide all the way back until the notch in the slide aligns with the takedown lever. Rotate the takedown lever 180 degrees. Pull the side assembly forward off of the frame. Pull the recoil assembly out of the rear opening in the slide. Push the barrel forward to remove the lock block, and then push the barrel back to lift it out of the slide. Along with several lubrication points that will need attention, don't forget to add a drop or two of special anti-seize grease where the barrel lug and locking block meet in order to keep the pistol running smoothly.
Because the Boberg action is built to tight tolerances, this gun is a bit more finicky when it comes to ammunition selection. To help customers keep track of the best ammunition options, the company posts a list in its online forum of the .45 ACP loads known to be compatible and incompatible. The information is derived from in-house testing along with customer feedback. When I was packing up for the shooting range, I stuck to the listed compatible loads.
The compact XR45-S provided a positive shooting experience, especially for a reduced-size pistol. Despite having an unloaded weight of just 22-oz., the pistol’s action measurably tamed felt recoil. The deep arch along the back of the grip and its narrow profile made it comfortable to hold. I was able to sneak my little finger mostly onto the grip. Folks with larger hands will most likely need to curl their pinkies under the grip. The smooth trigger was a real pleasure to work with and aided in solid shot placement. The XR45-S is nicely balanced, fast to get on target but it is slower to reload because of the manual removal of the magazine and the need to rack the slide when a fresh magazine is inserted.
The pistol fed, fired and ejected the test ammunition without any malfunctions. Usually I would conduct formal accuracy testing for a sub-compact pistol at 7 or 15 yards. But this pistol has a barrel the same length as many midsize semi-automatics and a good set of iron sights, so I went ahead and pushed the targets out to 25 yards for bench rested 5-shot groups. The best single 5-shot group of 2.79", and best five-group average of 3.09”, was produced using Hornady Critical Duty 220-gr. +P FlexLock loads. Liberty Ammunition Civil Defense 78-gr. +P copper hollow points averaged 3.20", followed by Winchester USA practice grade 230-gr. Full-metal-jacket loads at 3.40".
The Boberg XR45-S pistol represents a commendable piece of engineering that lives up to the company's promise of a big-bore pistol that is also compact, accurate and comfortable to shoot. It's obvious from the fit and finish, inside and out, that the company is dedicated to producing high-quality handguns. For those individuals who want to pack .45 ACP ammunition in a sub-compact pistol, the Boberg offerings definitely deserve consideration.
Manufacturer: Boberg Arms
Model: XR45-S Standard
Action: Rotating Barrel Locked-Breech Semi-Auto
Caliber: .45 ACP, .45 ACP +P
Slide: Satin Stainless Steel
Frame: Black Hard Anodized Aluminum
Grips: Textured Polymer
Sights: Low Profile 3-Dot
Barrel Length: 3.75”
Overall Length: 5.77”
Slide Width: 1.08"
Grip Width: 1.01”
Weight: 22.5 ozs. with magazine
Capacity: 6+1 Rounds
Rifle Grooves: 6
Accessories: 2 Magazines, Hard Case, Lock, Manual