upper

Primary Weapon Systems MK116 Pro Upper

 When it comes to AR upper receivers, there are a ton to choose from. You can get dirt cheap, or super hi-end. There’s also different ways for the firearm to cycle those upper receivers. One of those is the long stroke gas piston. Which leads us to Primary Weapon Systems (PWS for short). Primary Weapon System has been making long stroke gas piston AR uppers for some time, as well as complete rifles. PWS is well known for their long stroke gas piston AR’s and upper receivers.

  Primary Weapon Systems sent me one of their MK116 Pro Upper receivers. Which version they sent isn’t as important as how the upper operates. As all of the PWS uppers use the long stroke gas piston for operation. The long stroke gas piston operates differently than your standard AR’s direct impingement system. Instead of using the gas to cycle the Bolt Carrier rearward, the PWS long stroke gas piston uses a piston that is, essentially, directly hooked to the BCG through the piston rod. When gas comes into the gas block, it directly pushes on the piston to cycle the action. This gives a few advantages over the normal direct impingement system. For one, the gun runs cleaner because all the gas isn’t being directed directly into the action. It also allows the action to run cooler, since the hot gas isn’t being directly blown into the action. A big plus if you are running an upper on a full auto gun. Lastly, the action can tend to run smoother because all the operating parts are fixed together. There are also a few downsides to a long stroke piston upper. They can weigh a little more. The PWS upper is only a few ounces heavier than my comparable DI upper, so it’s not a lot of extra weight. The only other notable thing is that it comes apart differently than a DI upper. Not a big deal at all, just different.

  The PWS MK116 Pro upper has a lot of great features. First off, I’ll mention that I received the 16” barreled version. This is important to note because it uses a mid length gas system for the piston. It also has a 15” M-Lok handguard. The handguard is a little different then what most people are used to. This is because it is missing a small chunk of the top picatinny rail, or basically one lug of the rail. This lug is missing so that you can easily adjust the 3 position gas block. The MK116 also runs a slick side upper, so no forward assist. There is a small shell deflector on it to keep the ejected brass from hitting you, but it will hit your camera man in the face. This particular upper came with an A2 birdcage. If you want flash suppression, the A2 birdcage works very well. Lastly, the PWS MK116 comes with a Radian Raptor charging handle. I really like the Raptor charginging handles, PWS made a good choice in using them. 

Staking on Carrier bolts is different due to long stroke piston setup

  PWS gave the long stroke gas piston uppers, and firearms, a 3 position gas block. As mentioned earlier, this is easily adjusted through the handguard. One can even use the tip of a bullet to adjust it. The 3 positions are labeled 1,2,3, and “X”. All 3 positions have a detent and click to them. The X position is for disassembly and cleaning, it’s not a click adjustment. Position 1 is for unsuppressed use, or normal everyday use for those without a suppressor. Position 2 is for suppressed light loads or low back pressure (flow through) suppressors. Position 3 is for suppressed heavier loads or higher back pressure suppressors. I did try out all 3 positions. Position 1 works exactly as advertised. Position 2 would eject rounds without a suppressor, most of the time, Position 3 would not cycle without a suppressor. With my 556 suppressor, position 3 was spot on. Positions 1 and 2 had a bit of force behind the ejection pattern. I really like how PWS gives you a simple, yet effective, way to adjust the upper for suppressed and unsuppressed use. Through all my testing on the PWS upper, I had zero malfunctions, not counting the ones I caused by using the wrong gas position (I had to test them). I also used a variety of ammunition types and brands for testing, both suppressed and unsuppressed.

  Being that the Primary Weapon Systems MK116 was just a complete upper receiver, I needed something worthy of mounting it on. I ended up using an Aero Precision lower. This lower has a few options that make it a great companion to the PWS upper. The lower has a Blackout Defense Zero trigger installed in it, a VZ stipple grip, and an ambi safety selector. The trigger is what really makes such a great combo with the PWS long stroke piston. You can shoot this rifle super fast if you want to. Also, I needed to have some way to aim the rifle. I ended up using a 1x prism sight. Well, I did have a 1-6x on it at first, but I took it off in favor of the prism. The last thing I did to enhance the PWS upper was to install some NILE grip panels and a sling. The NILE panels use a M-Lok attachment, so they mounted up super easy to the PWS M-Lok rail. I had to use a M-Lok QD attachment for the sling. This particular PWS upper doesn’t have QD mounting points built into the handguard, that’s not a big deal for me, but it would be nice. I was really happy with how the PWS upper worked in conjunction with my lower receiver. The fit to the lower receiver was a bit tighter than what I would call “normal”, but not tight enough that it was hard to install on the lower. The PWS upper, when mated to my lower, made a really nice rifle.

  Anyone looking for a great way to upgrade an AR rifle, needs to look into the Primary Weapon Systems long stroke gas piston uppers. The PWS system works very well. The action is super smooth. The piston system is robust and will keep your rifle cleaner than the original gas system does. If you are using a suppressor, it also keeps the blowback gasses out of your face. So if you are searching for a top tier upper receiver, do yourself a favor and go check out what Primary Weapon Systems has to offer.

Firearms Insider Reviews - Key Points

Claim to Fame:

Long Stroke Gas Piston Upper

Target Market:

Those wanting a super reliable gas piston rifle

Features & Benefits of this product:

  • Operating System: PWS Long Stroke Piston System, 3 setting Adjustable Gas Regulator

  • Caliber: .223 Wylde

  • Barrel Length: 16.1”

  • Gas System Length: Mid-Length

  • Barrel Twist Rate: 1:8

  • Muzzle Device: A2 Flash Hider

  • Upper Receiver: PWS Proprietary Piston Upper, 6061 extrusion, Anodized

  • Handguard: PWS M-Lok™ 15” Handguard (1.7” width, 2.25” height)

  • Charging Handle: Radian Raptor™ Ambidextrous Charging Handle

What other aesthetic options or finishes are available?

PWS has a ton of different uppers, all are gas piston

What others are saying?:

Not much found

Link to other reviews:

Pew Pew Tactical full rifle review  

Price point:

MSRP = $824.95

Retail = Same

I need it now! Availability:

Primary Weapon Systems

Our Rating:

Pros:

  • Long Stroke piston

  • Radian Raptor charging handle

  • Adjustable gas block

  • Cut-out in handguard for gas block adjustment

  • Quality

Cons:

  • Cut-out in handguard for gas block adjustment

  • Proprietary system

  • Pricey

Score: 8.00 Great

Kaiser X-7 Blackbird receiver set

  When you think about lightweight AR’s, you usually don’t think of composite hybrids. Kaiser US is here to change that, and in a big way. Kaiser has plenty of experience in the hybrid AR market with great product success. Recently they introduced a new Titanium-Graphite composite AR15 receiver set called the X-7 Blackbird. The name pays tribute to the SR-71 Blackbird spy plane, a composite plane that was way ahead of it’s time, thus similar to the X-7 Blackbird receiver set. After having Mike, from Kaiser, on the podcast, he offered to send me one of these hot new Blackbird receiver sets for review.

  Let’s talk a little about this Ti-Graphite composite. There are a lot of misnomers about composite, or plastic, receivers. Even though some of these are true, they do not apply to the Kaiser X-7 Blackbird, or any of Kaiser’s other receivers. This is because Kaiser engineered the composite receiver, so it is not just your everyday “polymer” like the others. It has more material in certain places to help with strength. But Kaiser doesn’t stop there. They wanted it to be stronger than the standard aluminum AR15 receivers. So they put titanium and anodized aluminum inserts into the places needing strength. For instance, some of these places are the threads for the buffer tube and the barrel nut threads. The Blackbird’s Ti-Graphite composite also adds in some more strength, simply because the titanium and graphite are molded into the composite. Another huge advantage to the Ti-Graphite composite is its lubricity and wear resistance. Essentially, it is so smooth that very little to no lubrication is needed. I still put some oil on the BCG, but it cycled smoothly without it. So what does this Ti-Graphite composite get you? It yields a super strong upper/lower receiver set that weighs in at 9 ounces stripped. For comparison, a standard stripped, forged AR15 lower receiver, without an upper, weighs 8.8 ounces.

   Besides the Blackbird being a super lightweight receiver set, it also has some other enhancements. Up first is its textured magwell. Not only is it textured on the side, but the front as well. This texture consists of raised rectangles. For those of us that grab the magwell with your support hand, this gives you a good, no slip, grip on the Blackbird. The magwell is also beveled to help get those magazines changed quickly. Next is the fit between the upper and lower receiver. It’s tight! I have never had a matched receiver set fit like this before, in a good way. I can push the receiver pins out, hold the upper, and shake it vigorously before the two halves come apart. If you are using the Blackbird for a precision style rifle build, this fitment would be perfect and would definitely help in the accuracy department.

  With the X-7 Blackbird being engineered differently, it has a few slight differences. All of them are good, just different. First, since the lower receiver is slightly wider than a standard aluminum one, at least in some spots, it can’t use standard anti-walk pins to hold the trigger in place. Standard trigger pins will work, but there is no reason to use them. Kaiser gives you their proprietary V2 anti-walk trigger pins, as well as the allen wrenches to install them. These V2 pins work for any trigger you wish to install into the Blackbird lower. It pretty much accepts any mil-spec or drop in AR trigger. The X-7 Blackbird also uses a proprietary port door on the upper receiver. As with the trigger pins, the lightweight port door assembly is also included. Most standard and ambi safeties will work with the Blackbird. I installed a Timber Creek ambi safety and it works well. Because the Blackbird is about weight, Kaiser also includes a skeletonized titanium grip screw for mounting your favorite grip. I went with the old A2 style grip, because it is one of the lighter weight grips around. The Blackbird upper receiver also does not have a forward assist. My guess is to save weight, since the forward assist isn’t always needed. The last two differences have to do with assembling the lower and upper. Instead of being able to put the rear takedown pin spring in normal, it now goes under the pistol grip, similar to the safety detent. I have zero problems with this, it's just different enough to mention. When installing a barrel and handguard onto the Blackbird, Kaiser recommends the use of a “reaction rod”. This prevents the upper receiver from being over torqued and damaged. They also only recommend 30 ft lbs of torque on the barrel nut as to not cause any unseen damage to the receiver.

  A little bit about the build with the X-7 Blackbird receiver set, is in order. I wanted to try and make this build pretty light, since the Blackbird is so light to begin with. I basically took an assembled AR pistol and took it apart, that way I could use the lightweight parts on the Blackbird. These consisted of a Faxon Lightweight 10.5” pencil barrel, a Walker Defense Titanium BCG, a Dark Hour Defense Magnesium handguard, and some other miscellaneous parts. What this gave me was an AR pistol that weighed 4.2 lbs without an optic. That is with parts that one can buy everyday, no custom special parts here. If you were to put a small lightweight red dot on it, it wouldn’t weigh much more. I did install a larger red dot, a finger stop, and a light. This only brought the weight up to 5.2 pounds, which is respectable with a light. It is possible to get the Blackbird to below 4 lbs without sights, I just haven’t tried to do it yet. One could put a shorter handguard and some titanium small parts to help reduce the weight even more. I am happy with how this build turned out. When you pick it up next to my decked out 11.5” SBR, it feels like it weighs nothing.

  How does it shoot? “Fantastic” would be the first word to come out of my mouth. The Ti-Graphite composite makes it so smooth. There really is barely any recoil, partly due to the Ti BCG and adjustable gas block. But It’s smoother feeling than when the same parts were in a standard aluminum receiver set. Double taps are super easy and quick to make. Essentially, this lightweight Blackbird receiver set makes an awesome place to start your lightweight AR build. I’m sure full Blackbird rifles will be available soon if building isn’t your thing.

  In the end, if you are looking at a lightweight AR15 receiver set, the Kaiser Blackbird can help you out. This Ti-Graphite matched upper/lower receiver set is one of the strongest and lightest ones around. The Blackbird is way lighter than its nearest, more expensive competitor. Don’t be scared by those who say “plastic” will break, they haven’t used the Blackbird and they probably haven’t ever heard of Kaiser US either. So, if you want one of the lightest AR’s around, start with the Kaiser X-7 Blackbird receiver set and don’t look back. You’ll be getting a quality product that will perform above your expectations.

Firearms Insider Reviews - 8 Key Points

Claim to Fame:

Ultra lightweight AR15 receiver set

Target Market:

Anyone wanting a lightweight receiver set

FNBs (Features & Benefits of this product):

  • Titanium Graphite Composite Material

  • Titanium & anodized aluminum inserts at all critical wear points

  • Beveled mag well

  • Compatible with any Mil-Spec drop-in trigger

  • Compatible with all Mil-Spec and most aftermarket grips

  • X-7 Weight - 9 oz, for the complete receiver set

  • Non-Slip texture

  • Skeletonized Titanium Grip Screw included

  • Ejection Port Cover (EPC): Proprietary for X-7 EPC /Spring /Rods (Included)

  • V2 System: Anti-Walk Trigger Pins (included), Proprietary for X-7

  • Trigger Pin Screws and Allen wrenches included

  • No Forward Assist

  • Zero Corrosion

  • Impact Resistant

  • Maintenance: No Oil or Lubrication Necessary

What other aesthetic options or finishes are available?

Midnight Grey

What others are saying?:

Could only find stuff on the Monarch series

Link to other reviews:

Only found Monarch series reviews    

Price point:

MSRP = $375.00

Retail = $356.00 at Rainier Arms

I need it now! Availability:

Kaiser US

Our Rating:

Pros:

  • Super lightweight

  • Smooth operation

  • Tight upper/lower fit

  • Unique look

  • Includes anti-walk pins, port cover, and titanium grip screw

Cons:

  • Price, but lightweight always costs money

  • Slightly wider, in some places,  than standard AR lower receivers 

Score: 9.00 Amazing

Favorite Link:  Blackout Defense 

Expo Arms Patrol Series AR Upper

  Expo Arms has recently gotten into the AR-15 upper receiver market. They have a few options for pistols, SBR’s, and standard AR configurations. This particular upper is their Patrol series with a 16” barrel and A2 flash hider. If you didn’t know, Expo Arms is the in-house brand for Primary Arms and is sold exclusively through them.

  The Expo Arms Patrol Series is an everyday use AR-15 barrelled upper receiver. These do not come with a bolt carrier group (BCG) or charging handle. However when you order the upper, Primary Arms gives some drop down menus with discounted add ons, such as a BCG. The Patrol Series comes with a bunch of good specs: A 5.56 chamber, 1:7 twist nitrided 4150 cmv barrel, mid-length gas system, A2 flash hider, T-marked upper receiver, and a 15” M-Lok handguard.

  Barrels are an important part of any AR system. On 16” barrels, like this one, I like mid-length gas systems. They are smoother feeling and put less wear on components then a carbine length gas system. Being that the barrel is also salt bath nitrided, it will have a good lifespan and keep corrosion away. Expo Arms uses a SOCOM profile on the barrel. I like the profile as it gives strength and consistency without being heavy. Of course the muzzle is threaded and comes with an A2 flash hider installed. The barrel consistently shoots under 1 MOA for me with 69 grain match rounds. 

  Expo Arms uses their own T-marked upper receiver. This is a standard forged version made from 7075-T6 aluminum. It has a round style forward assist and a standard mil-spec port door. The whole upper is nicely machined and anodized. 

  To cover the barrel, and give you something to hold onto, is the 15” M-Lok handguard. This is a very nice, useful, no frills handguard. It runs a full top rail that is not sharp. The sharp parts of the rail have been deburred slightly. Along the other portions of the handguard are M-Lok slots. These M-Lok slots are every 45 degrees around the handguard, not just the standard of every 90. It’s a clamp on style handguard, but also has some anti-rotation tabs to keep it from rotating. I’ve never had a problem with these style handguards rotating on me, but the tabs are a nice addition. I really liked the Expo Arms handguard, I’d even consider it as a stand alone item. 

  If you’re looking for a good quality AR upper, the Expo Arms Patrol series might just be it. It has a lot of nice features for the price. In fact, I am still amazed at the 0.75” group I shot with it. Definitely go check out the Expo Arms series of stuff over at Primary Arms. 

Firearms Insider Reviews - 8 Key Points

Claim to Fame:

Quality 5.56 AR Upper receiver at a fair price

Target Market:

Anyone wanting a 16” AR upper

FNBs (Features & Benefits of this product):

  • 7075-T6 forged aluminum MIL-SPEC upper

  • 5.56 NATO chamber

  • T-Marked

  • 16" Patrol Series Nitride barrel

  • 41V50 Chrome Moly Vanadium Steel barrel

  • SOCOM barrel contour 

  • Mid-Length Gas System

  • 1:7 Twist Rate

  • 15" Expo Arms Patrol Series M-LOK Handguard

  • A2 Flash Hider

  • No BCG or Charging handle

What other aesthetic options or finishes are available?

Various

What others are saying?:

Nothing as of publishing

Link to other reviews:

Nothing as of publishing

Price point:

MSRP = $349.99

Retail = Check Primary Arms for sales

I need it now! Availability:

Primary Arms

Our Rating:

Pros:

  • Nitride Barrel

  • T-Marked upper

  • M-Lok handguard

  • Full top rail

  • Accurate

Cons:

  • Doesn’t come with BCG or CH (options are available)

Score: 8.50 Great

Favorite Link:  Walker Defense Nero Review

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