ArmaLite brings on the “Big Boy” AR-50

By Gary Reisenwitz

Ever wonder how new guns are designed? I used to wonder too. In a warm and cozy motor home parked on an Indian reservation in a remote part of South Dakota, during what was supposed to be the driest part of the year, it rained. Then it rained some more. When the sun occasionally pierced the drizzle to warm the high plains, we ventured out to do our part to eradicate the local prairie dogs that supposedly infested the area. Unfortunately, the ranch owners had little faith in our ability to control the critters, and had taken proactive population control measures a few months before. The miracles of modern chemistry had yielded precisely the effect that was advertised and very few of the now wary critters remained. Between the bad weather and lack of varmints to shoot, we had no choice but to design a new rifle. (Preferably one that would fire under water.) Actually, the trip was specifically planned with the primary purpose of brainstorming the rough design parameters of the ArmaLite AR-50 Rifle. We picked a great time to design a rifle, and a bad time to hunt prairie dogs.

Mark and Judy Westrom (President of ArmaLite, Inc. and Real Commander in Chief, respectively) wanted to build the .50 Caliber rifle “for the masses”. There were plenty of .50 Caliber rifles on the market, but they all suffered from the glaring defect of prohibitive cost. A lot of this “cost” is justified. The competitive .50 Caliber rifles are being sold as “sniper” rifles and “target” or “match-grade” rifles. There was no initial intent to market this rifle as a serious “match-grade” rifle. Mark felt that there were plenty of people that just wanted a .50 Caliber rifle, and would be willing to forgo the ultimate in accuracy in exchange for a reasonable reduction in cost. The initial goal was to produce an “economical” .50 Caliber rifle that would fall within the price range of the rest of the ArmaLite product line. The key to potential success in this project was to apply modern manufacturing techniques to a new, robust and simple design and produce the rifles in quantities sufficient to achieve the cost break. There never was any “rocket science” to building any of the commercially available .50 Caliber rifles. It is just that all others were made in such small lots as to preclude the economies of scale that can be obtained if the rifles are actually mass-produced. The modern production facilities that the ArmaLite folks are most familiar with are capable of the close tolerance reproducibility needed to make the critical components of the new rifle. Holding the tolerances in this manner precludes the time and cost prohibitive “fitting” required for all the other .50 Caliber rifles on the market. However, no matter how “clever” Mark and crew could be, there were many hurdles to overcome and these invariably affected the final cost and the delivery date.

Despite the many difficulties that lay ahead, many of the features that we agreed upon found their way into the production rifle. Mark Westrom, his wife Judy, myself, my wife Kim and Mark’s daughter Jeanelle Wanicki (operating a PC with a CAD package) worked as creatively as we could to “rough out” the design during that cold, wet Spring in South Dakota. We agreed upon the three-lug bolt design, a Sako styled extractor, spring loaded bolt-face ejector, V-grooved extruded aluminum stock with corresponding V shaped receiver bottom, screw type bolt stop, basic trigger configuration, three-bolt receiver/stock interface, conventional recoil lug, and a few other parameters that I’ve forgotten over the past two years. However, many hurdles remained before the ideas would turn to steel. The design of the muzzle brake would be Armalite’s Holy Grail and would be George Reynold’s most ambitious project. I think he exceeded everyone’s expectations, using the science he had mastered through years of experience in military weapon design to create a muzzle brake that would tame the recoil of the .50 Cal. unlike any had done before. I have to believe that this is the best muzzle brake ever designed for a .50 Cal. bolt gun. I’m not willing to say that it cannot be improved upon, but it’s darn good.

George took on the project of the production design of the AR-50 with a passion. He had spent the better part of his life as a small-arms designer at places like Aberdeen Proving Ground, Rodman Laboratories and Rock Island Arsenal, and took part in many design adventures, few of which unfortunately, ever saw the light of day. He worked with his son Paul as a father/son enterprise known as Knox Engineering, to serve as the chief engineer of the rifle design team. Most of the innovative features of the rifle evolved in the “bat cave” where the Knox Engineering machinery and instruments are kept and operated. (I’ve been promised a tour of the “bat cave” when I visit again.)

Progress continued and I’d get a package in the mail every few months with more bolt lug/receiver interface dimensions to go over for a “third look” for safety evaluation, and some nice CAD drawings of the final form of the AR-50 would show up as well. I was able to see the evolution of our rough design transformed into a real rifle. I was able to view the first prototype in steel and aluminum at the Shot Show in Atlanta this year, and was very impressed with how it turned out. I know that many orders for the rifle were placed on those few days the rifle was available for viewing.

More delays were encountered as barrel sources were sought, and innumerable computer problems plagued the company. Keep in mind that the demand for the rest of the ArmaLite line had exceeded their estimates, and their suppliers were also hit with an unexpected increase in market demand for all AR variants. The ArmaLite folks could not devote as much time to the AR-50 project as they wanted if they were going to remain solvent. The Y2K scare and new gun laws created a huge demand for all semi-automatic sporting rifles and the ArmaLite crew were hard pressed to do their part to meet the demand.

Finally, around the third week of October, 1999, the first of the new AR-50 rifles began to be shipped. I received mine a few days later. The work and waiting paid off. The box that it arrived in was huge. They ship these rifles fully assembled and they are just shy of 5 feet long. The packaging was the best I’d ever seen for a heavy firearm, and it is obvious that some considerable thought went into the safe packaging of this rifle for shipment. (I can’t count how many firearms I’ve received through UPS that had some portion of the firearm poking out from the side or end of the box.) This packaging was impressive. The rifle was well protected.

Taking it out of the box was easy enough. Finding a place to set it down to get a better look was a more difficult task. We settled on the dining room table. I had a few friends drop by to see the new arrival (with many more to venture by on the days ahead). Everyone was impressed. The only question was “when” and “where” were we all going to shoot the beast. We decided upon a remote range in northern Alabama, because they had at least a 200-yard distance to the backstop, and we thought it would be remote enough to avoid bothering people with the noise.

The weather was barely cooperating, with a heavy overcast and threat of rain. Unfortunately, hunting season was near and the range was in heavy use by the local hunters checking out the zeros on their deer rifles. No matter, we would wait our turn. We didn’t have to wait long. Once it came out of its box, and was assembled on the shooting bench, all eyes were focused on us. For the first shot, I thought it would be best to bore sight the rifle for the short-range (50 yd) test target. This was easy as I had the rifle supported on my shooting rest and rear bag, where it remained in a very stable position. Taking the bolt completely out, it is easily to see down the bore and then through the scope, to insure both are centered at the same point. Piece of cake. I then put the bolt back in, loaded a round and aimed at a short range target, a 4” orange plastic disk cut from the bottom of a Halloween pumpkin, nailed to the middle of a large piece of cardboard at about 50 yards down range.

After insuring everyone was ready, and had their ears plugged, I centered the cross hairs on the plastic disk and pulled the trigger.

To my very pleasant surprise, I was not injured! In fact, the recoil was far less than I expected, and I think less than any ordinary .308 rifle would impart. I was also surprised by the sound. It seems that this rifle presents more of a “crack” than a “boom” and you definitely feel the blast or pressure wave. I let some of the other members of our entourage shoot and Rob described the sensation as “being hit in the face with one of those inflatable plastic baseball bats, like clowns use”. Not being a clown (although frequently falsely accused), I really couldn’t relate to the experience, but many others in our group nodded in agreement.

Standing behind the rifle while others fired, was a little less pleasant. You really feel the concussion of firing far more if you are about six feet behind the shooter. Whether you are directly behind or off to the side did not seem to make much difference. However, if you stand close to 90 degrees and 15 feet away, it is much less noticeable.

We all took turns shooting. Everyone was impressed at the lack of discomfort. There was no doubt that the muzzle brake worked as designed. After a while, the joy of punching paper and plastic gave way to the joy of punching steel. We took a 5/16 inch thick piece of steel plate 100 yards down range and proceeded to put a couple of quarter sized holes in it. I wanted to try it out on thicker pieces, but neither I, nor anyone else was willing to haul anything heavier all the way down range. After the shooting, we all took a closer look at the rifle to examine the details of this new offering.

Description of Rifle

The rifle is nearly entirely made of metal. Forty-one pounds of metal. The only non-metallic parts are the recoil pad and the pistol grip. The recoil pad is very large and quite spongy. It works great. The pistol grip is the only readily identifiable part taken from the other Armalite rifles, and is a modified M16A2 type grip. The reason for this was to keep costs down and use a part already on hand. The beauty of this decision is that this makes it possible for the new owners to modify any of the aftermarket “AR” grips and easily customize their AR-50 with the grip of their choice. I can think of several I’d like to try.

The stock consists of two pieces of machined anodized aluminum. The forearm and forward portion of the stock is a single aluminum extrusion. It is extremely rigid, quite heavy and features a T-slot machined along its underside for mounting a bipod or other attachments. The buttstock is also machined from a single piece of aluminum and is secured to the forearm by three large socket head cap screws. (It will be replaced by a forging on later production rifles.) The buttstock features an adjustable cheek rest and an adjustable butt pad. The vertically sliding cheek rest has some insulation glued to it to provide some comfort and is retained by two button head machine screws. The cheek rest on this particular rifle had some sharp edges on it that needed some remedy. I have since been told that the rifles now being shipped have some black plastic edge banding to cure the problem. The vertically sliding butt pad is also secured by a pair of socket head cap screws, and permits a considerable range of adjustment.

The trigger guard is a machined and anodized aluminum forging that secures the grip. The assembly is secured directly to the receiver by a socket head cap screw (not just to the stock).

The trigger assembly is a very simple single stage trigger. This is probably the only part I think could use some improvement. The example I received had a very long engagement and a lot of annoying creep. I called ArmaLite about this and they got back to me right away with an apology that the trigger had not yet been adjusted. During the manufacturing process, the triggers were disassembled and machined to fit the rifle, and apparently, a few triggers were assembled into rifles without the “factory” adjustment completed. This results in a very safe trigger, as the maximum mechanical engagement is the default. I was assured that this was an anomaly and not indicative of their intention. The triggers are not intended to be adjusted by the user, but are supposed to be factory adjusted by ArmaLite to fire in the 3-4 pound range. I decided to forgo the adjustment for now, but don’t think I’ll have any trouble completing the task later.

The receiver is made from a massive bar of 4340 Chrome-Moly steel and is secured to the stock assembly with three socket head cap screws. At first glance it appears octagonal, but actually, the receiver is closer to being seven-sided. The top half has a typical octagonal profile, but the bottom half forms a deep ninety degree “V” rather than being flat, as a true octagon would require. There is a narrow flat machined on the very bottom of the “V” that is only about 5/16th” in width that forms the eighth side. The large receiver screws pull the V-shaped receiver down into the matching V-grooved stock. The third screw pulls the receiver to the rear of the stock, forcing the primary recoil lug into the front of the forward stock V-block, insuring the receiver cannot shift under recoil. The combination of the V-grooved stock, V-shaped receiver, massive recoil lug (captured between the barrel and the receiver) and rear receiver screw effectively ensure that the barreled receiver goes back into the stock the same way each time it is removed. This is especially useful as it is more difficult to transport the rifle fully assembled. (However, when disassembled, it does fit nicely into the large rifle case that ArmaLite sells.)

The bolt is a multi-piece assembly, but the main body and three locking lugs are machined from a single piece of 1.5” diameter 4340 bar stock. The bolt is retained in the receiver by a modified button head machine screw that is found at the left rear of the receiver. Removing the screw with a hex key is all that is required to enable the bolt to be completely withdrawn from the receiver. The bolt retaining machine screw also acts as the bolt guide, keeping the lugs in alignment as the bolt is worked in and out of battery. The decision to use three lugs was based on several factors. There was the self stabilizing feature of three lugs (like a tripod), the shorter bolt throw to engage and disengage (versus a two lug design) and the large surfaces areas and shear areas the three lugs would offer that helped make it all work. The extractor is similar in design to those used on the Sako rifles (and copied by lot of folks) and is coil spring activated. The ejector is a spring and plunger type fitted into the bolt face as in the AR-10, M15A2 and most modern rifles. The striker assembly is easily removed from the bolt body without any tools, by simply ensuring the striker is cocked and the safety is in the “safe” position, and unscrewing the entire cocking piece and striker assembly from the main bolt body. The bolt handle is very well proportioned for a rifle of this size, and on early guns is silver soldered onto the bolt body. There is also a roll pin that appears to secure the bolt handle, but it is there only to assist in initial alignment and assembly. Later bolt bodies will have the bolt handles attached by welding. There is a 1/4” hole in the side of the bolt, located about 2” back from the bolt face that serves as a gas port, in case of a pierced primer. The safety is conventional in design, and very simple in construction. It is massive for a purpose. The striker and spring are quite massive as well, and a very sturdy safety is required to be functional. It is stiff and difficult to apply, but this rifle was not designed to be carried anywhere in a loaded, ready-to-fire state. The safety is not likely to see much use on the bench.

The barrel is about 30” long, 4140 Chrome-Moly steel, custom made especially for ArmaLite and is capped by a threaded muzzle brake. The barrel is threaded into the receiver and also secures the massive front recoil lug. It is completely free-floated from the stock.

The muzzle brake looks like it came off a tank. It is made from two pieces of precision machined steel. The baffles are actually machined from a solid monolithic block of steel. The “cap” is retained by button headed machine screws, but is also relief machined to accept the baffles, ensuring that the screws are never subjected to shear stresses, just tensile stresses.

All the steel parts are parkerized to a near black finish and all the aluminum parts are hard coat anodized to a black finish.

The scope that was used is a Leupold 3.5×10 Vari-X III Tactical model. This is only a 1” tube scope that was not designed for use with .50 Caliber rifles, but it was available. The scope was mounted using the standard ArmaLite 1” scope mount and was attached to an aluminum riser block that ArmaLite produces exclusively for the rifle. These riser blocks are fitted with recoil shoulders that mate with corresponding milled recesses in the receiver to absolutely prevent shifting under recoil. The riser blocks are secured to the receiver with four 10-32 socket head cap screws. The top of the riser block is a standard Piccatinny rail and will interface with any number of scope mounts and ring types. The riser blocks are made in two different “sizes”. The “short range” riser block has a built in 15 mil elevation to ensure that your scope has enough vertical travel to engage targets out to 1000 yards. The “long range” riser has a 50 mil elevation built in to permit using a standard scope on targets from 500 to 1500 yards. Of course, you may not need more than one size if your scope has sufficient vertical travel, but not many scopes are designed as such. The option of the variable riser blocks solves this problem, and permits you to use the scope you already may have. I opted for the 15 mil riser block and used it for my initial testing.

(Some scopes are advertised as being designed for .50 Caliber use, while most simply do not discuss the potential. This rifle doesn’t recoil very much, and in my opinion, would not be as harsh on scopes as a typical 8 pound .308 hunting rifle.)

The Challenge!

Although this rifle was not designed for competitive marksmanship events to compete alongside custom made, hand tuned rifles; there was no reason to assume that it would not perform reasonably well at very long ranges. It turned out that hitting something at 1000 yards was not the challenge. The real challenge was finding a place to safely shoot at a target 1000 yards away. This may not be a problem in the far west, but in the southeast U.S., access to ranges capable of shooting 1000 yards is considerably more difficult. However, local interest in this rifle was very high, and with a few well-placed phone calls, the information surfaced, and the location became available. A local law enforcement firearms instructor had made arrangements for access to a nice flat cotton field with a 15 foot railroad embankment on the far end. His shooting buddy brought out a precision surveying transit (which included a range finder) and we were able to precisely place a large target frame at 1000 yards from our firing point.

The weather was very cooperative for a November morning. It was about 50 degrees outside and there was almost no wind. However, it was very hazy with morning fog, and the 1000 yard target was completely obscured. We felt it would burn off soon, so we began to set up and zero the rifle at a 200 yard target, using the less expensive standard US military Armor Piercing (AP) ammo. Once we got the zero, we set up a target at 500 yards, and re-set the elevation. Getting ready for the 1000 yard shot, we knew that an additional elevation adjustment was needed, so we estimated the amount of elevation and cranked it into the scope. Unfortunately, what we estimated exceeded the adjustment capacity of the Leupold Vari-X III that we were using. The haze burned off to the point where the 1000 yard target was visible (with the scope!) and I tried one round of AP to see where we might strike. The shot struck up the dust a considerable distance in front of the target. This was not encouraging. However, we decided to try the HSM match ammo to see if the lower drag bullets would make a difference, and we got lucky. The first two shots of the HSM struck the 1000 yard target about 24” to the right of my aiming point and about 4” high. The two holes were about 10 inches apart from each other. We were on paper at 1000 yards with less than 20 shots fired.

The aiming point that we were using at 1000 yards was piece of fluorescent poster board about 12” x 18” in size, taped to a piece of cardboard covered in butcher paper forming a background that was about 4’ tall and 6’ wide. For the rest of the morning, four of us took turns shooting groups and trying to move the zero around, with groups that ranged from 8” to 14.5” in size. It was very clear to us that this rifle/ammo combination is capable of sub-Minute of Angle (MOA) accuracy at 1000 yards. Keep in mind that this rifle was nearly brand new, two of us had never fired ANY rifle at 1000 yards before, the trigger was pretty bad, the haze between us and the target never completely dissipated, we were limited to a 10 power scope and only one of us could really be classified as a “marksman”. We all felt that with actual practice, less haze, a decent trigger and better scope, that we should have been able to do better than we did. If this had only been the experience of one shooter, you could make the claim of beginner’s luck, but all four of us were able to shoot very well at the 1000 yard target.

Improvements?

All first production guns have a few bugs that get worked out. The only “bug” I could find was a trigger that just wasn’t “perfect”. It worked fine, never malfunctioned, just didn’t “feel” good. However, I was told that this was merely a matter of adjustment and I will rectify it before I take it out again.

I’d really like to see ArmaLite build a real heavy-duty bipod for this gun. They offer a bipod adapter for a Harris bipod, but a Harris bipod and a 41-pound rifle is just not my idea of a good combination. I also think this rifle could greatly benefit from a rear buttstock mono-pod, as was used in some light machine-guns. The rear mono-pod when used with a good bipod (especially if the bipod is equipped with a small traverse capability) effectively turns the rifle into a tripod. This would be very useful when firing from the prone position. Finally, I’d offer a carrying handle at the point of balance along the barrel. It would make the rifle much easier to move around when firing from the prone position. Something like the BAR or M60 MG carrying handle would be nice.

Although not a function of the rifle itself, this rifle needs good optics to realize its potential. The art of really long range shooting requires features on scopes that are really not required for shooting at shorter ranges. Some of the features that I believe a fully capable scope should possess, for 1000 yard (and beyond) shooting are as follows:

•Parallax adjustment Parallax is the amount the cross-hairs on a scope move, on the target, as your eye moves laterally, in relation to the central axis of the scope. If you can ensure that you head and eyes are in exactly the same position for each and every shot, it may not matter. However, not many of us have a T&E device built into our necks. A parallax adjustment will enable the shooter to focus the scope at the target at a particular range, and simultaneously adjust the scope so that there is no perceptible parallax error that can be introduced at that particular range. Parallax adjustable scopes usually have a ring on the front or rear bell of the scope to turn to make this adjustment, but others have a third knob on the scope body for this purpose. I find the central third knob to be easier to use. A parallax error at 1000 yards can exceed 12”.

•Scope Level A spirit level, either built into, or attached onto, the scope tube will enable the shooter to keep the scope cross-hairs level on the target. Canting the scope even a few degrees can cause a bullet to miss the target by several feet at 1000 yards. These are inexpensive to attach, and some of the nicer scopes have them built into the field of view.

•Magnification I believe that 20X is a good level of magnification for a rifle capable of shooting at 1000 yards. More magnification than 20X just seems to reduce clarity too much, but at 10X, it was difficult to keep from totally obscuring the target with the cross-hairs.

•Durability The recoil is very manageable on this rifle, and is not likely to damage any good quality scope. However you still have to be concerned with bumps and knocks when handling and moving the rifle. Once you get 41+ pounds of metal moving, it wants to keep on moving, and a light duty scope and mount could easily be damaged though rough handling. My guess is that a variable power scope would be more fragile than a fixed power scope, so I’d opt for the fixed power version for this application.

Safety

A word has to be said about safety when shooting .50 Caliber BMG firearms. The maximum ordinate range of the .50 Cal BMG ammunition is extreme. As long as you are shooting at a good backstop, though, you should not have problems. There are some concerns about the Armor Piercing ammunition and ricochets. Because the hard steel core will not disintegrate when hitting dirt, there is a chance the core will bounce off the ground and carry some distance down range. Once again, a tumbling ricochet is not going to go as far as any ordinary hunting bullet that is not tumbling. It is a bigger bullet, and it does go a little farther, but the same rules of safety that pertain to shooting any high powered rifle apply to the .50 Caliber shooters.

The only ammunition that may pose a safety concern to the shooter is SLAP (Sabot Light Armor Penetrator) ammunition. The SLAP projectile uses a discarding plastic sabot to support a lighter, smaller bullet. This ammunition has excellent armor penetration characteristics, but was not designed to be fired from rifles with muzzle brakes. Upon firing such ammunition from any .50 Caliber rifle with a muzzle brake, plastic fragments may be blown back toward the shooter with dangerous results.

Sources:

AR-50 Rifles
ArmaLite, Inc.
P.O. Box 299
Geneseo, IL 61254
Ph. (309) 944-6939
Fax: (309) 944-6949
http://www.armalite.com

.50 Cal. Match Grade Ammunition
The Hunting Shack
P.O. Box 7465
Missoula, MT 59807
Ph. (406) 777-2106
FAX: (406) 777-3908
http://www.montana.com/hsm/