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Wolf A1 Gas Piston AR-15 Upper Receiver Review

Got the AR blahs? Get out of your rut with Wolf's new A1 gas piston AR-15 upper receiver.

Wolf A1 Gas Piston AR-15 Upper Receiver Review
Got the AR DI blues? Spice things up with Wolf’s new 5.56x45mm Gas Piston A1 upper receiver assembly which comes complete and ready to drop on your lower.

Wolf Performance Ammunition’s distinctive logo has long been synonymous with economical steel cased ammunition, match grade .22 LR and high quality shotshells. While Wolf has traditionally sourced their ammunition from Europe, a few years ago they partnered with an arsenal in Taiwan. This allowed them to add a high quality brass cased 55-grain FMJ .223 Rem load to their extensive line-up. Produced by the 205th Armory of Combined Service Forces, and marketed under the Wolf Gold banner, it quickly became very popular due to its quality, accuracy and price. This successful partnership with Taiwan’s 205th Armory has recently led to an interesting new offering from Wolf, a short-stroke gas piston AR upper receiver assembly called simply, the A1.

While gas piston AR’s have not really caught on the looks of this one might get your attention. Based on the Taiwanese Type 91 infantry rifle, it performed flawlessly.

In recent years Wolf has been steadily expanding their offerings beyond ammunition. In 2013 they added an optics division which today offers both day sights as well as Gen 3 night vision devices. Plus they entered the AR market with an economical 16 inch 6.5mm Grendel upper receiver assembly to fire the inexpensive steel case Grendel ammunition they are flooding the market with. Their latest project is a 16 inch 5.56x45mm AR upper, but it’s actually quite different than other offerings on the market. It seems in addition to producing high quality ammunition Taiwan’s 205th Armory is also home to Taiwan’s current combat rifle, the Type 91. The new gas piston upper receiver being offered by Wolf is a sporting variant of the Type 91. This is a very high quality piece which is fully compatible with any standard AR-15 lower receiver.

Wolf’s new upper receiver features a short-stroke gas piston operating system. It drops onto any standard AR-15 receiver.

What I like best about Wolf’s A1 upper receiver is it’s not simply a commercial design; it’s a well proven military piece. When piston guns first became popular a number of models appeared on the US commercial market. Despite grandiose claims, most of these ended up having issues. Typical problems included shearing the piston tappet key off the bolt carrier, broken tappets, broken pistons and carrier tilt. All of these designs needed to go through an evolutionary process to sort problems and in the end most Americans decided to stick with Stoner’s DI system.

A Wolf WPA PSU 1x/4x32mm scope which had just survived a 5,000 round torture test was used during testing. Performance of the dual magnification optic was excellent.

Wolf’s new 5.56x45mm NATO Gas Piston A1 upper is a very different animal though compared to these American commercial designs. Rather than being developed for use by American sportsmen, the Type 91 was designed to provide overmatch to the best the People’s Liberation Army of Communist China can field in a life and death struggle. Keep in mind, Taiwan is an island. If Communist China should invade there is no retreat, only victory or death. Not only must a Taiwanese infantry rifle be reliable and accurate under the harshest conditions, but it must offer a rifleman an advantage over that wielded by his much more numerous foe. In this regard the Taiwanese Type 91 is notably superior to the Communists’ older 7.62x39mm Type 81 and offers many advantages over their latest 5.8x42mm Type 95.

With that in mind let’s take a look at Wolf’s new Gas Piston A1 upper receiver. The unit comes nicely boxed, complete and ready to drop onto your AR-15 lower receiver. The only thing missing is a rear sight or the optic of your choice. The heart of the piece is a flattop upper receiver assembly with a 1913 rail for mounting iron sights or an optic. A “slick side” design, it does not have the typical A2 forward assist or case deflector. The look is somewhat “old school” which I liked.

The upper is fitted with a cold hammer forged barrel 0.66-inch in diameter with a 1-7 inch twist. Note the combination flash suppressor/compensator.

Inside the upper rides a familiar looking bolt carrier assembly. A closer look reveals a one-piece bolt carrier with an integrally machined tappet key. This ensures a long and trouble-free service life. The bolt, cam pin, firing pin and firing pin retainer all look like standard AR parts. Removing the bolt from the carrier though reveals it is not cut for gas rings. The entire bolt carrier assembly is manufactured to Taiwanese military specifications. At the rear of the upper receiver you’ll find a standard GI type charging handle.

The two piece polymer handguards feature a top and bottom section locked into place by one captive cross-pin.

Fitted to the front of the receiver is a 16-inch cold hammer forged barrel. This measures 0.66-inch just in front of the chamber and runs this diameter to the muzzle. Barrel twist is 1-7 inch, which I prefer and it features a 5.56x45mm NATO chamber. The barrel is held in place by a beefy barrel nut noticeably longer than a standard A2 piece. Moving to muzzle you’ll find standard 1/2x28 threads allowing any standard muzzle device to be fitted. However, the A1 comes with a pretty interesting combination flash suppressor/compensator identical in concept to SureFire’s expensive WarComp 556. The design features slots and a closed bottom like a traditional A2 flash suppressor. However, it also features three rows of three round ports to reduce muzzle rise. These nine small holes are biased to the right to reduce muzzle rise for a right-handed shooter. A beefy locking nut allows it to be easily timed biased to the right, left or in a neutral position.

A robust gas block/front sight base is securely pinned in place. A traditional A1 type front sight post sits well protected by heavy duty ears. The front sight is adjustable for elevation when zeroing. On the left side of the gas block is a robust spring-loaded retainer for the gas piston assembly. Push this in and rotate it 180-degrees to unlock the gas piston assembly which is visible at the front of the gas block. Next, rotate the gas piston assembly 180-degrees and the entire unit can be pulled from the front of the gas block. Both the retainer and piston assembly are designed to allow a cartridge or tool to be inserted for added leverage if the piece is badly fouled.

The stripped bolt carrier assembly looks very familiar, note the integral tappet key machined into the carrier and the lack of gas rings on the bolt.

The “Rapid Clean” piston assembly pops out the front as a self-contained captured unit complete with gas regulator, piston, spring and tappet housed inside a metal container. In operation gas is vented through an orifice in the barrel into the gas block which in turn vents it into what I will call the regulator. Gas entering the body of the regulator comes in contact with the head of the piston and pushes it to the rear. The piston pushes the tappet which comes in contact with the tappet key machined into the bolt carrier. After a very short movement of approximately 0.25-inch the piston has moved far enough to the rear to expose two small round vents at 3 and 9 O’clock on the regulator. Any extra gas is vented from the system through these holes. The bolt carrier continues its rearward cycle while the tappet spring returns the tappet/piston assembly to its original position. Operation is very straight-forward, all components are easily accessed and maintenance is “old school” simple.

A look under the hood with the handguards and piston assembly removed. Note how the piston assembly comes out as one captured unit.

Surrounding the barrel and piston assembly is a set of heat resistant polymer handguards consisting of a top and bottom piece. The bottom piece is flat on the bottom to sit squarely on available support and ribbed for a secure grip. It also features an aluminum heatshield. The top piece has ventilation slots to aid cooling and two threaded inserts at 12 O’clock. The threaded inserts allow accessories, such as the sights for the T85 40mm under-barrel grenade launcher, to be easily mounted. The handguards are retained by one captive pin. So removing and installing them is relatively easy with no Delta ring to wrestle with.

A look at the piston assembly installed with the handguards removed.

Out of the box the WPA Gas Piston A1 upper receiver looked well-made and nicely finished. I had zero problems installing it on a half a dozen different lower receivers from various manufacturers. For my initial testing it was mounted onto a registered selective fire lower receiver and subjected to numerous full automatic magazine dumps. The Wolf upper not only ran flawlessly on full automatic, but it also proved very controllable. Cyclic rate was approximately 600 rpm and it proved very smooth shooting, thanks in part to the compensator. Short bursts, long bursts or 30 rounds at a time were no problem.

Next I moved to the bench, added a Carl Zeiss 6.5-20x50mm Conquest scope in a LaRue SPR scope mount, and checked accuracy. This was done using a semi-automatic lower fitted with a Geissele SSA-E trigger and an H2 buffer. Four 5-shot groups were fired from a rest at 100 yards with velocity readings recorded using a LabRadar unit. Test ammunition consisted of Black Hills’ 69 grain Open Tip Match and their 77 grain Tipped Match King, Winchester’s 77 grain PDX1 Defender and Wolf Performance Ammunition’s brass case 55 grain FMJ-BT from their Gold line.


At right is the gas regulator while at left is the piston with attached tappet.

Taking my time shooting slowly from a rest I noted rounds chambered smoothly and extracted and ejected cleanly. Accuracy was quite good with Winchester’s 77 grain PDX1 Defender load posting the tightest average at 1.7 inches. Wolf Performance Ammunition’s 55 grain FMJ-BT load was right behind it though, averaging 1.9 inches. Black Hills Ammunition’s 77 grain Tipped Match King load averaged 2 inches while their 69 grain OTM load averaged 2.5 inches. No issues were encountered, but I did notice the compensator pushed the sight picture slightly to the left firing from the bench.

The piston assembly strips easily for cleaning.

Moving from the bench I swapped a Wolf WPA PSU 1x/4x32mm scope for the Zeiss. With the PSU mounted up, I ran the WPA A1 upper through a variety of drills engaging multiple targets from 5 to 50 yards. No problems or malfunctions of any type were encountered so I moved to position shooting on steel silhouettes at 200 and 300 yards. Here I engaged targets standing, kneeling, sitting, supported and unsupported prone. At these commonly encountered distances the WPA A1 did very well if I did my part.

Accuracy was quite acceptable as this 5-shot 100 yard group fired with Wolf Gold 55 grain FMJ-BT demonstrates.

Shooting prone off the magazine at 300 yards provided hits on steel as rapidly as I could realign the reticle and break the shot. I had just finished sprucing up my rifle range with new berms at 450, 500, 550 and 580 yards so I decided to see what Wolf’s A1 upper could do. Using Black Hills’ 77-grain TMK load I had no problem making consistent hits at 450 and 500 yards. I made frequent hits at 550 and 580 yards if I stayed up on the wind and watched the fundamentals.

After spending time shooting from the bench steel silhouettes were engaged from the offhand, kneeling, sitting and prone position with excellent results.

Wolf’s WPA Gas Piston A1 upper receiver saw 3,000 rounds during testing and had zero problems of any kind. I found the handguard to be comfortable in the hands and the flat bottom proved stable on improvised rests. The recoil impulse is smooth and fairly light. The muzzle device does indeed add some compensating effect to reduce muzzle rise. During lowlight testing I found there to be more flash than a standard A2 flash suppressor, but out of the rifleman’s line of sight.

Wolf’s 1x/4x32mm PSU scope proved fast on target on 1x and able to range and hit distant targets when switched to 4x.

Overall the design is very simple and easy to maintain. Learning how to take it apart and put it back together is very simple. It comes apart easily for cleaning and the fouling is mostly contained in the gas block, regulator and piston. The bolt carrier assembly and upper receiver remain relatively clean, especially compared to a standard DI AR-15. If you hate cleaning a standard AR, then you will really like Wolf’s A1 upper. After firing thousands of rounds through Wolf’s Gas Piston A1 upper I came away very impressed. It’s an interesting and well refined military design now available at a reasonable price. The Wolf Gas Piston A1 upper and the PSU 1x/4x32mm scope are each priced at $599.99. If either strikes your fancy you can call 888-757-9653 to locate a dealer.

A smooth recoil impulse and compensator made for a flat shooting and easy to control piece.


Wolf Performance Arms Gas Piston A1 Upper Receiver Specifications

  • Caliber: 5.56x45mm NATO
  • Operation: Short Stroke Gas with rotating bolt
  • Barrel: 16 inches, cold hammer forged 4150 steel, Nitride treated
  • Barrel twist: 1-7 inches
  • Muzzle threads: 1/2x28
  • Muzzle device: Combination flash suppressor and compensator
  • Iron Sights: Protected front post, no rear sight included
  • Optics Rail: Yes, MIL STD 1913
  • Handguard: Heat resistant polymer with heat shield
  • Price: $599.99

Wolf WPA Gas Piston A1 Upper Receiver Accuracy Chart

Notes: Accuracy results are averages of four five-shot groups fired from a rest at 100 yards. Velocity figures are 20-shot averages recorded with a LabRadar Doppler chronograph at an ambient temperature of 55 degrees F at 1,030 feet above Sea Level.

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