PWS MK111 Mod 2 Upper Receiver

Short answer:  If you plan to purchase or build a high quality upper for your NFA toys, just buy a PWS.

Prior to the 2016 election, my only panic buying was to get my SBR and Suppressor applications in to the ATF.  With my tax stamps in hand, I dove into the world of suppressed SBR AR-15s.  What I found wasn't pretty.  First off, discount parts weren't going to cut it.  SBR's put a lot more stress on the action and gas system than it was originally designed.  A can exacerbates that.  Not to mention the additional fouling that makes its way into the action of a DI rifle.  Since tax stamps are such a PITA, I decided not to skimp on a rifle would probably never see another owner.  My SBR lower is an Aero Precision Ambi with BCM LPK, Magpul furniture, PWS buffer assembly, AXTS Talon ambi-safety, and HiperFire 24E trigger.

I wanted to build the lightest upper possible to offset the weight of the can, with an 11" barrel to minimize length with the can attached yet still maintain good velocity and reasonable gas pressures that wont beat the action to death.  Originally I went with an SLR adjustable gas block and a Bootleg adjustable bolt carrier for gas regulation.  The SLR is set for PMC Bronze unsuppressed, with any subsequent gas adjustment done from the carrier.

Here's the cost breakdown of my upper build.

Bootleg Upper: 159.95
Bootleg Port Door Assy: 9.95
Bootleg Adj Bolt Carrier: 249.95
Bootleg Bolt: 79.95

BCM KMR Alpha10 Handguard: 179.95
BCM Gas Tube: 14.00

AXTS Raptor Ch. Handle: 89.95

Faxxon 11.5" Barrel: 149.00

SLR Sentry6 Gas Block: 119:99

Surefire Socom556 Muzzle Brake: 149.00

RailScales HTP Scales: 29.00

Total 1,230.69

What I didn't realize at the time was that I was basically building a DI version of what PWS already makes with a piston.  More on that later.

After getting everything assembled and torqued I hit the range.  Everything went great until I attached my Surefire 762 Mini.  I chose the 7.62 version for caliber versatility, and I figured the larger bore would reduce back pressure. I knew that suppressed SBRs were dirty but I didn't realize how bad it could be.  I was shooting 3-5 round strings of Federal M193, not Wolf or PMC, but even outdoors and moving, my eyes were watering after just a few rounds.  Support side was even worse. While I could tolerate this during a zeroing session or an actual encounter, this was something I didn't want to have to deal with during a defensive rifle class or at my indoor range.  I knew I wanted a piston upper.  I'd been looking at piston uppers for the past few years, but the drawbacks and cost held me back.  Most of the systems used heavy short-stroke pistons.  These often come with heavy profiled barrels, gas blocks that are large enough to limit rail length, carrier tilt, and reports of spotty reliability.  I knew PWS made a long-stroke AR, but I dismissed them as too expensive and assumed a long-stroke design would be heavier.  The release of their Mod2 line changed my thinking.

The first obvious change was that they incorporated the Bootleg lightweight upper into their build.  While this eliminates the forward assist, none of my current uppers have one, both as a weight saving measure and because I've never needed to use it.  The Picmod rail is skeletonized with Keymod on 3,6, and 9 o'clock as well as picatinny rails on the forward sections.

PWS MK111 Mod2 Upper: 1,349.95

Compared to my SBR build, the difference is 119.26  When factoring the included Triad flash hider and BCM Ch. handle vs Surefire brake and Raptor Ch. handle the difference is $238.31

While nearly $240 is nothing to sneeze at, PWS uppers often sell for $100 less.  Now factor the cost of shipping from multiple vendors and the difference shrinks to less than $100.  Do you already own all the tools needed to assemble an upper?  A torque wrench, action block, or armorer's wrench will set you back $50 each.

All the referenced prices are MSRPs.  I sourced the original upper parts while I waited for my suppressor Form4 to clear.  I had months to scour the web for deals and wait for price specials.  For the PWS upper, I asked a few Facebook friends to point me toward a Mk111 Mod2 and had one in my hands in 4 days.  My actual cost difference all in for both uppers was ~$100.

When the postman handed me the 28" long black cardboard box, I must have looked like a kid on Christmas morning.  I tore it open, and as I stared at the beautifully machined and anodized upper, a painful realization hit me.  There was nothing more to do.  No parts and tools to gather, no Googling torque specs, no assembly.  As a guy who actually enjoys putting together Ikea furniture, this was quite a a letdown.  But then I saw the BCM sling mount and the RailScales, and then I remembered I still had to transfer over my buis, MRO, Raptor charging handle, Karve handstop, X300U, and Surefire muzzle brake.  Since PWS specifies an H2 buffer with their rifles, and I was going out of town, I used the $25 gift card to purchase theirs.

A week later, I finally got some time to hit the range.  I set the gas block to position 3 (suppressed full power ammo), attached my can, set a target down range at 100 yards, and fired my first 3 shot group from sandbags using PMC Bronze .223.  PMC is known for being pretty weak and I wanted to see how the gun functioned.

1st 3 shots @ 100 yards

I'm pretty happy with that.  I didn't clean or lube the upper prior to firing.  As I got my red dot and BUIS dialed in, every so often the bolt would fail to strip off the next round.  Thinking it was the weak PMC, I tried XM193 5.56, but the same thing happened.  Checking the manual, I learned that setting 3 is for suppressors and heavy ammo, 62 to 77 grains.  I turned the gas block to setting 2, and experienced zero failures afterward.  I removed my suppressor and even though I left the gas block on setting 2, it still functioned flawlessly even with low powered PMC.  I didn't notice a difference in recoil but even with the can, the gas coming back through the action was much less than with an unsuppressed DI.  The real test came when shooting defensive drills.  This is where PWS's system shines.  Excess gas no longer vents a few inches from my head.  No matter the shooting position, I could breathe deep, my glasses stayed clean, and my eyes never watered.  After 6 full Pmags of ammo, I broke down the action to check for fouling and wear.

After 180 rounds

After 180 Rounds

After 180 rounds

After 180 rounds

After 180 rounds

There was no evidence of carrier tilt or any abnormal wear.  The bolt and carrier were lightly coated in a mix of factory grease and fouling, but the guts of the carrier and bolt return spring were clean.  Nothing was baked on or crusty.  The nooks and crannies in the receiver and trigger well were no dirtier than my handguns get.  Getting the bolt carrier out is a little more involved than with a DI gun since the BCG and charging handle have to come out together.  It was a minor annoyance during repeated bore cleanings at break-in, but a worth while trade off compared to scraping the bolt.  I always keep a spare bolt and gas rings handy for my DI uppers.  I'll have to inquire with PWS about spare parts.  All the parts wiped clean with just a patch soaked in Slip 2000 725 Cleaner.  I only needed 4 patches to clean the upper, BCG, and lower.  Keep in mind that only about 15 of the 180 rounds were shot unsuppressed.

Bolt Group Cleaned

Lower Cleaned

Upper Cleaned

I currently have a Griffin Recce5 5.56 can waiting in NFA jail, so I don't know how the upper will perform with a dedicated 5.56 can.  I can say that the recoil impulse feels softer than my DI guns.  It feels like the difference between a mallet and a dead-blow hammer.  When the bolt locks back on the last round, the impact of the bolt feels almost muffled somehow.  It's probably due to the gas acting on the piston over a long period and the added weight of the piston rod slowing the carrier speeds.  Needless to say, I like it

I can't say how happy I am with the PWS MK111 Mod2 Upper.  I've already ordered their MK114 a 14.5" upper that I plan to pin a Griffin Flash Comp for my non-NFA lower.  To pay for it, I'm selling my DI uppers.

-Carry On.