Wednesday, February 21, 2024

Adcor Defense BEAR Gas Piston Rifle (GPR): Gas Piston/Op-Rod-Driven Tactical AR Rifle/Carbine/SBR with Forward Charging Handle and Free-Float Barrel (Video)

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By David Crane
defrev (at) gmail (dot) com

April 21, 2011
Updated on 4/21/11.

A company called Adcor Defense is manufacturing and marketing a new gas piston/op-rod (operating rod) tactical AR (AR-15) rifle/carbine/SBR (Short Barreled Rifle) called the B.E.A.R. Gas Piston Rifle (GPR). “B.E.A.R.” is an acronym that stands for “Brown Enhanced Automatic Rifle”, since the weapon was designed and developed by Michael J. Brown. Piston-driven tactical ARs aren’t exactly uncommon these days, but what is uncommon is Adcor’s left-side-situated forward charging handle (FCH) system, which would seem to offer superior ergonomics to the traditional rear charging handle setup, except for one caveat, which was recently pointed out (in late January 2011) by “militarymoron” of (MM) fame (excellent site!) in a thread on the AXTS A-DAC fully-ambidextrous lower receiver. In response to “couch potato’s” proposition that the Adcor BEAR GPR’s forward charging handle system and A-DAC ambi AR lower with mag-release-activated bolt catch would go together like chocolate and peanut butter (my phrasing), “militarymoron” wrote:

i dunno about that. the ADCOR BEAR sticks the forward charging handle right where i like to mount a light (for thumb activation), and precludes mounting a rail panel right where i need it.

“militarymoron” makes a valid point. If you like to stick your thumb-activated tactical white light on the left side of the rail where he likes it, then the Adcor GPR’s forward charging handle may not be for you, but it’s still worth checking out, since you can just move the FCH to the other side of the rail system/forend rail tube like a lefty would do, which is indeed doable, since the FCH is ambidextrous/side-switchable. This would seem to be a viable solution for “militarymoron’s” tactical accessory integration dilemma, as all he’d have to do to operate a right-side-situated forward charging handle is slightly rotate the gun to the left, first. I mean, it ain’t rocket science. It’s perhaps not optimal, ergonomically, but it’s still pretty fast and easy.

And, for all those AR traditionalists out there, good news: the Adcor Defense B.E.A.R. Gas Piston Rifle tactical AR retains the traditional rear-situated AR charging handle. So, the forward charging handle just offers you an additional/alternative weapon-charging/bolt carrier group (BCG)-cycling solution without losing your traditional setup.

Adcor GPR’s other major differentiating features from other systems are a (claimed) completely free-floating barrel for optimal accuracy, quasi-monolithic rail system (forend rail tube is separate from receiver but with exceptionally tight lock up), and “tool-less” design, in that you can take down the weapon for cleaning and maintenance with just your firing pin. Like the Primary Weapons Systems (PWS) long-stroke gas piston/op-rod system, the Adcor Defense BEAR GPR’s piston/op-rod assembly is permanently attached to the bolt carrier group, supposedly preventing bolt carrier tilt by completely doing away with the hammering action on the bolt carrier key/strike key and running the op-rod through a bushing in the rail system. And, the piston pulls right out the front for cleaning and maintenance, a la the Adams Arms Distributor Piston, POF P-415, and Barrett REC7 piston systems, while the op-rod/BCG assembly slides out the back of the upper receiver, just like normal takedown.

Defense Review hasn’t yet had an opportunity to T&E the Adcor Defense BEAR GPR at the range, yet, nor have we seen any detailed testing data on it, so we have no idea how it will perform under adverse conditions and high round count. We’ll try to get our hands on a copy of the H.P. White Lab-conducted 6,000-round MIL-C-7186 test report on the BEAR GPR for review and analysis.

Adcor Defense B.E.A.R. Gas Piston Rifle (GPR) Upper Receiver Features:

– Piston/Op-Rod System
– True Free-Floating Barrel
– Ejection Port Dust Wiper With Cover
– Removable Folding Front Sight (Front BUIS)
– Ambidextrous Forward Placed Charging Handle/Forward Assist Lever
– Fully Integrated Mil-Std-1913 “Picatinny” Rail System
– Adjustable Cyclic Rate of Fire (ROF) via the Rotating Gas Plug in front of the Gas Block
– Tool-less Design

The following information comes from the Adcor Defense website:

New Piston System:

– The new top portion of the rifle includes a gas-driven piston incorporated into the upper half of the forward rail system. The system does not touch the barrel.
– The design of the gas piston system and operation rod completely eliminates carrier tilt.
– This design ensures reliability by preventing hot gases and carbon particulates from entering the receiver and fouling the chamber and the action. Diminished heat reaching the upper receiver means that Cleaner Lubricant and Preservative (“CLP”) applied in this area will evaporate at a lower rate and not dry out. The design allows less maintenance and increases the overall reliability of the weapon.
– A newly designed vent cover houses the piston exhaust ports, which protects the operator from exhaust heat and cuts down on the weapon’s signature.
– Mounting the piston on the underside of the rail system allows the barrel to float freely, ensuring greater accuracy of the weapon.
– The lower half of the rail system detaches with a unique tool free design for ready access to the piston and gas tube for operational maintenance and cleaning. The operating system can be cleaned faster than the existing weapon’s cleaning routine.
– The operator in the field can adjust the piston’s cyclical rate to keep the carbine operating within control rate of fire parameters, resulting in less wear on the carbine’s critical parts.
– The piston design is machined with close tolerances so that gas rings are not needed, eliminating another potential maintenance issue for the weapon.

Exclusive Ejection Port Dust Wiper With Cover:

– After a typical AR carbine fires, the weapon is susceptible to contaminants because the ejection port door remains open until it is manually closed. Dust, sand and debris can enter the receiver and work their way between the receiver and bolt, potentially jamming the carbine. These contaminants also create wear and maintenance issues.
– Adcor’s design solves this problem with a spring-loaded dust cover mounted on the carbine’s bolt carrier. Each time the weapon fires and the bolt carrier returns to the ready position, the dust cover moves into the ejection port opening, flush with the outside geometry of the carbine. No dust, sand or debris can enter the weapon.
– There is a biasing device, comprised of two springs, between the bolt carrier and the shield for biasing the shield outwardly away from the bolt carrier so that the dust cover shield continuously engages the inner surface of the receiver during movement in the firing and rearward positions.
– The shield is formed of a self-lubricating polymeric material that can withstand extreme heat and cold, and is extremely durable.

Ambidextrous Forward Placed Charging Handle/Forward Placed Assist

– Adcor’s design permits an operator to charge, clear or forward assist the weapon without losing any engagement with the target. The operator reaches forward and pulls back on a handle (which can be located on either side of the weapon for right or left handed operators) without losing sight of the target.
– If the carbine jams, the same handle clears the carbine with a single pull. It is an easy-to-use single mechanism.
– The handle is detachable (without tools) and is ambidextrous for use on either side of the weapon.
– It is equipped with a spring that returns the handle to a locked position once used, where the handle folds forward into a recessed area to keep it out of the way. To use the handle again, the operator reaches forward, swings the handle outward and back in a single motion.

– The handle does not move back and forth when the weapons fires, but only engages when the operator charges or clears the weapon.

Rail System:

– The new key locked, highly rigid rail system mounts seamlessly to the upper receiver.
– The upper rail guard and lower rail guard separate using a unique tool-less push button feature.
– The design ensures proper alignment of the rail with a redesigned boss, spline and groove system.
– The rail will not “spread” or fall out of time. The Adcor rail system is compatible with all accessory items such as optical sights, image intensification sights, thermal sights, laser targeting systems, bipods, tactical lights, Multiple Integrated Laser Engagement System (MILES) of the existing AR platform.”

The following information comes from the Adcor Defense GPR flyer (PDF format):

“Adcor currently manufactures AR piston weapons with barrel lengths ranging from 10” to 24” for both .223 and 5.56 calibers, along with receivers and rail systems for both gas impingement and piston style weapons.


– Piston system for cleaner more reliable operations
– Free oating barrel for improved accuracy
– Dust wiper to protect upper receiver and components
– Removable folding front piston sight for ease of cleaning
– Ambidextrous forward placed charging/forward assist handle to help maintain target acquisition
– Fully integrated rail system
– Adjustable cyclic rates for use with different ammunition or suppressors
– Toolless maintenance system allowing components to be removed with bullet or ring pin

Adcor weapons underwent a 6,000 round MIL-C-7186 test, conducted by HP White Laboratory, Inc., with zero failures or stoppages. The accuracy testing with a 14.5” barrel yielded groupings of .88” at 100 yards.

The Adcor 10” GPW is the weapon of choice for Baltimore City SWAT.”

Company Contact Info:

Adcor Defense
234 South Haven Street
Baltimore, Maryland 21224
Toll Free Phone: 888-612-3267
Fax: 410-522-3597
Email Contact Page:

© Copyright 2011 All rights reserved. This material may not be published, broadcast, rewritten or redistributed without receiving permission and providing proper credit and appropriate links.

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About David Crane

David Crane started publishing online in 2001. Since that time, governments, military organizations, Special Operators (i.e. professional trigger pullers), agencies, and civilian tactical shooters the world over have come to depend on Defense Review as the authoritative source of news and information on "the latest and greatest" in the field of military defense and tactical technology and hardware, including tactical firearms, ammunition, equipment, gear, and training.

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