Adcor Defense 5.56 x 45mm Semi-Auto B.E.A.R. (Brown Enhanced Automatic Rifle)

UPDATED with new Two-position Regulator Direct Gas Impingement System

by Jeff Quinn

photography by Jeff Quinn & Boge Quinn

October 29th, 2011

UPDATED January 13th, 2012





Click pictures for a larger version.



Adcor direct-impingement system has a two-position gas regulator.

Magpul telescoping buttstock.



Magpul pistol grip.





Forward-mounted charging handle.



Gas regulator.



Magpul folding sights.



Two-piece handguard.









Back in October of last year I reviewed a very innovative AR-15 platform rifle from Adcor Defense. This rifle used a free-floating gas piston system with several unique and useful features. The rifle functioned perfectly, and the adjustable gas regulator is very useful to have, if using a variety of ammunition, or for use with a sound suppressor.

Now, Adcor has integrated their two-position gas regulator for use with the simple and reliable gas impingement system, which has served well for decades on the AR-15/M-16/M-4 platform rifles. This regulator is marked for use with either 5.56mm or 223 Remington ammunition, and is a very good feature to have that option, as most gas impingement system rifles are marked for one cartridge and not the other. To get 223 rifles to function well with 5.56mm NATO ammunition in standard rifles, the higher-pressure 5.56 ammo works the action too hard, accelerating wear and parts breakage. 5.56mm NATO rifles will work with 223 Remington ammo, but only if they also accelerate wear when using the high pressure NATO ammunition. A rifle set up properly to run smoothly using only 5.56mm ammo will sometimes not function properly when loaded with 223 sporting ammunition. The Adcor adjustable system solves this problem, and allows optimum pressure regulation for using either cartridge, and will also regulate pressure better when using a suppressor (silencer) or when the weapon becomes dry and dirty, or when using sub-standard ammo.

The Adcor gas impingement rifle functioned perfectly, and exhibited excellent accuracy. To change the regulator position, all that is needed is a bullet or other pointed object, to push in the retaining pin, allowing the regulator to rotate, or to be removed for cleaning. To check the regulator, I set the position for 5.56mm NATO ammo, and loaded the rifle with 223. Sure enough, it would not cycle, but rotating the regulator to the proper 223 position, the weapon cycled flawlessly. This is a very good, reliable gas system to use on an AR-15 rifle. This Adcor rifle also has all the great features of their piston gun, such as the dust seal on the chamber, and the forward reversible charging handle. The Adcor solves the problem of using 5.56mm ammo in a 223 rifle, and that of using 223 sporting ammo in a 5.56mm NATO chamber. Great idea!

A couple of months ago I received a package containing what appeared to be an AR-15. I opened it up, but finding no info packed inside the box, I just gave it a quick glance. Good-looking AR, with rails, M-4 profile barrel, telescoping buttstock, and flash suppressor. Very popular configuration, but I figured it was just an AR like dozens of others, and set the box aside. That was a mistake. As I retrieved other weapons from the gun room for review, I would notice the box with the AR, and planned to get to it later. Finally, after it sitting patiently awaiting its turn on the range, I opened the box, removed the weapon, and took a closer look.

There are many variations of the AR-15/M-16 rifle system on the market today, with some straying farther from the original concept than others, and at some point, the question has to be asked; “When is an AR no longer an AR?” The subject of this piece, and the weapon to which I referred in the preceding paragraph, looks like an AR, but is not an AR.

The Brown Enhanced Automatic Rifle has wandered far from the original AR concept, but shares some of the better features of the Ar-15 with that wonderful and innovative rifle. To be clear, I love the AR-15. Properly set up, it is one of the most accurate and reliable semi-automatic rifles ever produced. It is ergonomically superb. The weapon is easy to shoot, fits almost any shooter, is relatively lightweight, and beautifully accurate. The B.E.A.R. retains all of those qualities, but has a unique upper half that takes the AR design and makes it more user-friendly, and more resistant to dust and sand contamination.

The BEAR gas system differs from the direct impingement system of the AR, but the BEAR piston also differs from any other piston system of which I am aware. The BEAR piston is very simple, requiring few parts and no O-ring seals or piston rings of any kind. The gas system parts are built to such close tolerances that none are needed. Most uniquely, the BEAR gas piston does not contact the barrel, but is instead supported solely by the upper hand guard, which is mounted rigidly to the upper receiver. Adcor claims that this free-floating system improves accuracy, and judging by the results exhibited by this sample rifle, they have a right to make that claim. The only connection between the barrel and the piston system is the small gas tube, leading from the gas block to the regulator block. The regulator block does not touch the barrel. The regulator has two positions, easily changed, to allow the operator to go from a suppressed weapon to one without, and to also adjust for dirty or weak ammunition. The piston taps the rod, which is securely attached to the bolt carrier. Carrier tilt is a complaint often voiced by users of other piston guns, but the rod on this BEAR travels through guides in the upper hand guard, eliminating carrier tilt in the buffer tube.

As mentioned, the upper hand guard is unique, is a critical part of the BEAR rifle system, and is not just an afterthought, as on most AR rifles. As is popular, the hand guard contains plenty of Picatinny rail to accommodate accessories for the weapon. Rigidly attached to the upper receiver, the upper hand guard supports the piston system, and with the piston rod, guides the carrier as mentioned above. It also is dovetail-mated to the lower hand guard, which can quickly and easily be detached from the upper guard to expose the gas system for disassembly and maintenance. The accompanying pictures and video will explain this better than I can with the keyboard. It is a very unique and innovative design.

On the bolt carrier is a dust wiper. The BEAR has a dust cover, as do most AR-style rifles, but the dust wiper is in addition to the cover. After the weapon is fired, a dust cover stays open until manually closed. The dust wiper seals the upper receiver from intrusion by sand, dirt, snow, etc. after each shot is fired. If the bolt is closed, the dust wiper is sealing the ejection port from contamination. The polymer wiper is attached to the carrier, and is spring-loaded to seal the ejection port as the bolt closes. Great idea, especially for those in dusty environments.

Another really innovative feature is the charging handle that rides in the upper hand guard. The BEAR also has the standard AR-style charging handle, but in addition to that, there is the folding, ambidextrous charging handle up front. This is a very handy feature, especially if the weapon wears an optical sight, like the Hi-Lux CMR shown here. Also, the weapon’s action can be cycled with the buttstock firmly planted on the shooter’s shoulder. The operator can keep the weapon on target, and still cycle the bolt carrier. The forward charging handle does not reciprocate with the bolt, but stays in place while firing. It is also easily reversed for use by right-handed and left-handed shooters, without tools.

The Adcor BEAR wears a Magpul telescoping six-position buttstock and Magpul pistol grip. The grip has a storage compartment inside. The rifle also comes supplied with two Magpul P-Mag magazines, which are some of the best available, but can use any AR-15/M-16 5.56mm/223 compatible magazine. For bench work, I prefer the twenty-round surplus magazines from the US-Vietnam war era.

Speaking of bench work, for accuracy testing, I mounted my mule; the Leupold Mark 4 8.5 to 25 power target/tactical scope. This scope allows me to get all the accuracy that I possibly can out of a rifle/ammo combo. Velocity testing was done with the chronograph set out twelve feet from the muzzle at an elevation of 541 feet above sea level, approximately. Temperatures hovered around the seventy-five degree Fahrenheit mark during all velocity testing. Velocity readings are the average of several shots fired, and the results are listed in the chart below. Velocity readings are listed in feet-per-second (fps). Bullet weights are listed in grains. FMJ is a full metal jacket bullet. HP is hollowpoint. V-Max is a polymer-tipped varmint bullet. TSX is a Barnes Triple Shock homogenous copper hollowpoint bullet. The handload listed uses the TSX bullet with 24.5 grains of Ramshot TAC powder, a Remington small rifle primer, and Winchester commercial .223 Remington cases. Accuracy results are listed below in inches, and are the average of four groups with each type of ammunition. Accuracy testing was done with the rifle resting in a Target Shooting, Inc. Model 1000 rifle rest, to eliminate as much shooter error as possible. The rifle was allowed to cool between each brand of ammo tested.

Ammunition Bullet Weight Velocity Accuracy
Stryker V-Max 55 2854 0.375"
Lake City M855 62 3012 0.75"
Hand Load TSX 62 2766 0.88"
Winchester USA FMJ 62 2820 2.00"
Buffalo Bore HP 77 2701 0.50"
Black Hills HP 69 2536 0.82"
Wolf Gold HP 75 2443 1.25"

The BEAR proved to be very accurate with most ammo, acceptably so with some, and superbly accurate with the Buffalo Bore, Stryker, and even the military green-tip ammunition. Functioning was perfect with most ammo tested, but the Stryker V-Max load did not have sufficient energy to completely cycle the bolt, with the gas regulator in either position. Everything else tried functioned perfectly.

After accuracy testing, I tried out a new scope on the Adcor BEAR rifle. The Hi-Lux CMR series scope proved to be a rugged, reliable optic. The BEAR came supplied with some very good Magpul folding backup sights, but like most folks, I prefer an optical sight on my rifles. The CMR has a 30mm main tube and an illuminated reticle with ranging capabilities. It has variable magnification from one to four power, making it useful in close quarters and also out to moderate ranges. The CMR has multi-coated lenses, and a bright, clear image through the scope. It is a very versatile scope, and appears to be well-made. I mounted the Hi-Lux atop the Adcor BEAR using a one-piece mount from CDNN Investments. These are some dandy scope mounts for a Picatinny rail, and are very inexpensive.

The Adcor BEAR exceeded all of my expectations. It is a rugged, reliable, accurate rifle of innovative design, well-executed, exhibiting superb craftsmanship. It is certainly not another “me too” AR-15 rifle. Weighing in at seven pounds with its sixteen inch FNH hammer-forged barrel, it balances very well, shoots accurately, and promises to be a very good rifle design for the twenty-first century.

Check out the BEAR rifles online at

To order high quality 5.56x45mm and 223 Remington ammunition online, go to,, and

To look at the Hi-Lux line of scopes, go to

To order the scope mount shown here, go to

To order the 3 Bucc brass catcher, go to

Jeff Quinn

NOTE: All load data posted on this web site are for educational purposes only. Neither the author nor assume any responsibility for the use or misuse of this data. The data indicated were arrived at using specialized equipment under conditions not necessarily comparable to those encountered by the potential user of this data.  Always use data from respected loading manuals and begin working up loads at least 10% below the loads indicated in the source manual.

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Click pictures for a larger version.



Adcor Defense BEAR (Brown Enhanced Automatic Rifle).






Hi-Lux CMR scope.



Hi-Lux CMR Ranging Reticle.



Target Shooting, Inc. Model 1000 rifle rest.







Gas piston system.



Dust wiper.