At SHOT SHOW 2004, HK had all the publicity they had hoped for with their new piston operated upper receiver for the M4 Carbine. The M4D was deemed to be a huge leap forward in the battle to make the M16 family of weapons more reliable. The system boasts desirable features such as a railed handguard, a hammer forged bolt and carrier, and a chrome lined barrel. Unfortunately, it also "features" an extravagant price tag that will be far out of the reach for most. What most people didn’t realize, however, was that there was another, much more reasonable, piston based upper at that same show.

Frank DeSoma, the owner of POF-USA, had originally come across the idea of a piston based AR15 system when discussing the manufacturing complexities of another piston system with its creator. Frank took a look at the system from a mechanical standpoint, and designed a simpler version of a piston upper with parts that are already available. The system adds only four parts, a gas block w/ attached tube, FAL gas plug, a modified FAL piston, and a mechanical carrier.

With this being the original prototype, several things are different from Frank’s production version. On the current prototype the bolt carrier key is screwed and staked as usual, but it is also welded on. There’s no chance that it will shear off, unlike the "Rhino" gas piston conversion of the early 1980s. The production version will be of a different, improved design. I can’t talk about it here, but it does sound very promising. Also, there hasn’t been a decision on what type of gas block to expect, a "gas trap" or the current system.

The Predator handguard itself is a bit of a mystery to me, as I’m not a huge fan of "raised rail" systems. It’s fully machined from aircraft grade aluminum, and is VERY sturdy. There’s almost no lateral or vertical deflection when installed. No kidding, this rail has surprised me. I have to say that Frank came up with an innovative way to mount iron sights as well. On the "X" model rails he manufactures, the rail extends from front sight base to the rear of the receiver so the sights can be mounted on the rail. This can be good, or bad, depending on the usage. With a Trijicon ACOG, it’s too high for normal use… But when using a gasmask, it puts the sight right where it needs to be. I should also mention that POF-USA manufactures a fixed front sight for their Picatinny railed gas block, which just happens to be the same height as the upper receiver.

The rail also adheres completely to the critical dimensions of the M1913 Picatinny rail spec, unlike most other rails we tested which deviated on at least two (sometimes all four!) rails. All accessories tested worked great with the handguard, nothing slid around or rattled about on it. The handguard is also very light to be as sturdy as it is. During "static" deflection testing (hanging weights off of the handguard while the upper is placed in a vice) the upper exhibited minimal amounts of movement. During dynamic deflection tests (striking the handguard with a rubber mallet while the upper is placed in a vice) the system performed similarly.

When it comes to function, it’s hard to beat this upper. We did mud testing (similar to HK’s testing), sustained fire testing, and performed general neglect and abuse. There were over 10,000 rounds fired through the gun before I received it, and nearly another 5200 rounds fired through it afterwards. Beta C-Mag and 30 round mag dumps plagued this poor upper until we completely wore the chamber out. Most of the firing was full-auto through post-86 sample lower receivers with various weight and quality ammunition and different lower parts. No problems to speak of.

We did, however, have a problem with a rusty chamber (the production guns will have chrome lined bores and chambers, the pre-production did not) which was easily fixed with about 10 minutes with a chamber brush and a fine emery cloth. During the mud testing, I emptied two quarts of Southeast Texas red clay, sand, and water mixed into a pudding like substance directly onto the closed, charged bolt of the upper as well as the portion of the gas system underneath the handguard. After firing three 30 round magazines through the rifle with no malfunctions, it was evident that it had handled the mud fairly well. As long as the mud doesn’t enter the chamber, the gun will work fine. Like the total ham-fisted spastic retard that I can sometimes be, I washed the upper off with a water hose and went about firing the rifle for another half hour. Not thinking, I left the rifle in that dirty, wet state overnight and what did I get? A chamber that looked like a toilet in a public restroom at a truck stop. I doubt anyone would leave their gun in a similar state for any amount of time, but it does reinforce why "fighting" weapons of any type should have chrome lined barrels and bores.

Cleaning the upper was a breeze, as the only things that really got dirty were the chamber and the bore, and they weren’t really all that dirty. The chromed bolt and carrier really made the task as simple as can be. I have cleaned the gun once during the entire time that I’ve had it. The POF upper ran the same dirty, wet, or whatever.

The upper was one of the more fun to shoot of any I’ve tried, as there was very little recoil at all. It might be in part due to the 16" heavy barrel adding forward weight (fluted M4 barrels will be available on production units), the Bob Davies RROC compensator, or the piston operation. By whatever means, it was a riot to shoot, as all of the 10+ people that fired it agreed. With a cyclic rate that starts out at 560 RPM (with a X buffer) and is at most 675 RPM (with a standard CAR buffer) it’s extremely easy to control.

Now to the downsides to the upper… The Predator is a heck of a rail system for the price, but I believe that the raised upper rail does preclude usage of several optics, like the Trijicon ACOG. The raised rail helps with rapid acquisition of targets with the EOTech and Aimpoint, but it’s not all that easy to get a comfortable cheek-weld with the ACOG. The handguard is also rather wide for most people to grip with standard rail panel covers. It’s just shy of 2.90" in diameter with Tango Down panels, as opposed to the 2.38" of the Daniel Defense with the same panels or the 2.75" I have huge hands, so it isn’t a problem for me, but a few of the more petite shooters were preferring to grip the Tango Down Vertical Battle Grip. Magpul low profile rail panels are another solution to that problem, as they cut down on the horizontal girth of the system by about 0.35".

So, what’s the final verdict? For around $925-975, the system is a lot of bang for the buck. It’s an ultra-reliable upper that comes with a free float railed handguard, chrome lined and fluted M4 profile Douglas barrel, the utterly amazing Troy rear Battle Sights, detachable front sight, and the complete bolt, carrier, charging handle assembly and costs of a good direct gas impingement upper with a rail system and none of the extras. What more can you ask for?

-Cap’n

Anyone? Comments?

-Cap'n

Sounds very nice. Can we see the innards of the system?

It'll be interesting to pit the KKF gas piston up against this one.

Quoted: Anyone? Comments? -Cap'n

Cap'n I and a friend are very interested. We have been looking at the HKSl8 becasue of it's clean and reliable action, and had about given up hope on a gas piston AR system. I do have several questions from both of us:

1) will the upper be available only in 5.56 or will other calibers be available.
2) what parts will be interchangable with a standard AR15
3) what warranty will be offered
4) what type of steel is used for barrel/steel components (4140, 4150?)
5) are all aluminum parts forged, or are there any cast parts, if so, what are they?
6) will the barrel definitely have a chrome lined bore and chamber?
7) will a 1:7 twist ratio be offered.
8) what is the piston made of (4140 steel, stainless steel etc).
9) will the standard buffer spring system be used, or is there a forward operating rod?
10)how will the piston impinge upon the bolt assembly
11) can you provide photos of the actual gas system, both external and disassembled?
12) does the system shoot clean (ie keep carbon and residue out of the chamber/upper receiver/mag well)
13) what finishes will be offered?
14) will spare parts be available for purchase if a rifle is purchased?


Thanks!

Capn_Crunch

Did you get my IM Message?

strobe

Thanks, Capn, I'm excited, in general, about the whole gas-piston movement. Will be interesting to see if any of the various vendors becomes a stand out performer. I'll also be interested to learn how many SCAR submissions, if any, were gas-piston designs.

By the way, did you test this for accuracy?

John

-----------------
6.5 Grendel: AR10 Soul in an AR15 Body
www.65grendel.com

Looks and sounds sweet.

How much does this setup weigh?

Knowing the configuration of the SCAR submissions would provide a good point of comparison. That said, I'm not really a fan of POF'sPredator  rail (no offense), & would interested to know if any other aftermarket rail units would be compatible w/ this new uppper? Also, how accurate is the current iteration of this design?

Quoted: Knowing the configuration of the SCAR submissions would provide a good point of comparison. That said, I'm not really a fan of POF'sPredator  rail (no offense), & would interested to know if any other aftermarket rail units would be compatible w/ this new uppper? Also, how accurate is the current iteration of this design?

My thoughts exactly on other after market rail systems working with this upper.  Also, let me ask a stupid question here. ACOGs were originaly designed to be mounted on top of a carry handle right? How is the Predator rail giving a worse cheekweld than that? Or, is it only a bad cheekweld when compared to a regular flat top

I dont think any current rail systems would work. The pistion and gas tube are quite bigger than a standard tube. I think the M4 handguards on the HK are bigger.

Will post updates Monday, we've got electical problems at the house so online time until then is limited.

Strobe, got your IM, will update accordingly tomorrow. BTW, glad to see you on the board!

-Cap'n

great review Cap'n, now to get Frank to give me one for a few weeks of testing...................

Capn_Crunch,

Hop you get the electrical problems fixed.

strobe

Quoted: What more can you ask for?

The ability to order one and have it here next week?

Seriously, it is not much different than the Shrike. Looks good, but can't seem to get delivery of. I am waiting on a lot of things from POF to become orderable - MP5 part sets, MP5 Magazines, G3/MP5 Navy Lowers, etc.

Ive never had any trouble ordering things from POF, I guess ive had good luck to get stuff before its sold out and waiting for more

Capn_Crunch,

Any more info yet?

strobe

.

Capn_Crunch,

Have you given up on finishing the report?

strobe

Capn_Crunch

Well

strobe

tagged.

Take it back to 300yds, against a real M4, and see which gun makes smaller groups...

Unless you manage to add accuracy by chaning the operating system, this is a solution looking for a problem.

The normal AR system is functionally reliable (eg it can shoot a full combat load of ammo (far less than 5200 rds) without jamming due to lack of cleaning... It's also more accurate than any comparable piston-op gun (note, COMPARABLE. A $3000 'match' M21 is not 'comparable' to a rack grade M16A2)...

I dunno, Dave; the Daewoo DR200 I had was as accurate as any AR I've ever seen (as long as you used 55grn ammo in it, with it's 1-in-12 barrel).

Quoted: Capn_Crunch, Have you given up on finishing the report? strobe

Frank has ADD and has long since forgotten about this project.

ian187,

You may want to look at the latest Shotgun News.
We will begin our sale of this patent pending gas-piston uppers at the
2004 SAR (Small Arms Review), in Phoenix, AZ., December 3-5.
The test mule Capn_Crunch tested was one of our first test units that was on display
at the 2004 Shot Show. We have made great enhancements to the current gas-piston
uppers for the AR15/M16.
Best regards,

Frank
POF-USA

Quoted: ian187, You may want to look at the latest Shotgun News. We will begin our sale of this patent pending gas-piston uppers at the 2004 SAR (Small Arms Review), in Phoenix, AZ., December 3-5. The test mule Capn_Crunch tested was one of our first test units that was on display at the 2004 Shot Show. We have made great enhancements to the current gas-piston uppers for the AR15/M16. Best regards, Frank POF-USA

Please continue to keep us posted. There are those of us who would very much like a piston upper for our A15s.

Quoted: ian187, You may want to look at the latest Shotgun News. We will begin our sale of this patent pending gas-piston uppers at the 2004 SAR (Small Arms Review), in Phoenix, AZ., December 3-5. The test mule Capn_Crunch tested was one of our first test units that was on display at the 2004 Shot Show. We have made great enhancements to the current gas-piston uppers for the AR15/M16. Best regards, Frank POF-USA

Cost? If it isn't public yet, shoot me an IM.

i'll stick with a normal AR thank you

I personally have met Frank and have fired one of his full auto ARs with his gas system and they run beautifly, they help keep all the crap out of the chamber and really keep the bolt almost spotless. Only thing that I hated was that the range I met him at only allowed full autos to be fired while sitting.

tagged untill I can read this

Quoted: ian187, You may want to look at the latest Shotgun News. We will begin our sale of this patent pending gas-piston uppers at the 2004 SAR (Small Arms Review), in Phoenix, AZ., December 3-5. The test mule Capn_Crunch tested was one of our first test units that was on display at the 2004 Shot Show. We have made great enhancements to the current gas-piston uppers for the AR15/M16. Best regards, Frank POF-USA

I'll be there, I look forward to meeting you in person.

By the way, I hope you didn't take what I said seriously.

I'm interested if the cost has come down now that the system is in actual production?


"Happiness is a warm gun" -John Lennon

Yer furniture doesnt match.

Got a chance to meet Frank last weekend and try out his 11.5" system.  In auto it has about 2/3 the recoil impluse of a 20" M16 and in semi about 2/3 the recoil impulse of the M4 system.  the 11.5" was cycling around 645rpm in auto...a little more than half of what a standard  full auto 11.5" carbine runs.....nice an controllable.  The other benefits of the system is it runs super clean and cool, even in auto it doesn't seem to get very hot or retain heat.

Can't wait to see the next revision Frank brings out, once some of the kinks are worked out...this will be one bad ass system.

The price  quoted was not too bad either.....substantially less than other systems.

Where can I find more information about the KKFpiston upper?

Tsh77769

I wish I would have seen this earlier.  Great review Cap'n!

Nice review but NO way in heck is that handguard to the M1913 spec.
1) Groove down the middle is not spec and precludes the use of KAC type foward grips.

2) Rails look like they are missing the 'neck' (area from the underside of the angle to the where it connects to the tube or receiver.  (see the diagram on page 4 of MIL-STD 1913).

I take it you can clean the gas piston by removing the FAL gas plug? That is a neat feature.  You mentioned the welding of the gas key - can you post a pic of the final design of the bolt carrier when it comes out?  Since the gas key is designed to direct gas into the bolt carrier I'd imagine they could redesign the key to better work with the piston.

Quoted: Can't wait to see the next revision Frank brings out, once some of the kinks are worked out...this will be one bad ass system.

Frank hasn't brought the first model out yet so I would be more excited to just see something...anything...really.  

The 11.5" carbines we were shooting used Rock River Lowers with RRA/BM 6 postions stocks. The Bolt carrier has been modified to work with the piston and though it resembles a standard M16 Bolt assembly, it has some unique features....not going to let the cat out of the bag....  Frank was working on adjusting the gas system so it cycled better in Auto.....ran fine in semi..but had some hang ups in auto.

The Predator handguard covered in MAGPUL  Rail Protectors stayed cool to the touch after dumping several mags down range full-auto. Not a bad system and from pics I've seen, stong enough to hold up a car.

According to Frank the upper will us a standard 1913 spec  gas block so any detachable front sight can be used. He said he plans to use Troy flip up front and rear sights as standard when the upper comes to market. He said he planned to have around 50 units ready for the SAR show in Dec.

Also said he was thinking about making lowers  and would mark them with the pictogram feature found on newer HK's.


All in all a pretty neat system. Might just have to get one when they come out.

Tag

Here is the copy of the e-mails between Frank and myself. hopefully this will answer some others questions also.

Sent : Thursday, October 14, 2004 12:28 AM
To: [email protected]
Subject : AR15.Com Email :: Dwimmerlaik :: Gas Piston Upper

What is the price of the gas piston system now that it is in production?
Will there be kits available for the do it yourself type?


FROM:            "POF-USA" <[email protected]> | Save Address  
DATE:    Thu, 14 Oct 2004 06:58:44 -0700  
TO:    [email protected]  
SUBJECT:    re: AR15.Com Email : Gas Piston Upper  


  The Price is ONLY: $975.00
This includes:

POF-USA M4 heavy fluted chrome lined barrel
Mil-spec flat top upper receiver and charging handle
Vortec flash hider
Predator free floating tactical rail system with sling/bi-pod attachment
Magpul rail covers
Removalable front site
Troy Ind. rear flip up site
POF-USA Gas-Piston system (Picatinnay gas block/tube, gas plug, gas piston, op-rod)
POF-USA Gas-Piston  Bolt Carrier assemble w/mechanical key (NO Gas Ring/Exhaust Holes)

Our gas-piston upper come standard using C.R.O.S (tm)  (Crossion Resistant Operating System)
Chrome plated and chrome lined:
Barrel
Picatinny gas block/tube
Gas plug
Gas piston
Bolt
Extractor
Cam Pin
Firing Pin
Bolt Carrier

We will build and sell complete uppers only. We are proving our customers a very rugged system with MANY options as STANDARD, at a conservative price. Thanks for the inquiry. Let us know if we can assist you.
Best regards,

Frank
POF-USA
www.POF-USA.com
[email protected]
623-561-9572 wk
623-321-1680 fax

Now, $975.00 may be a "conservative price" for an upper with all that stuff on it to some but I won't be in that line for quite some time unfortunately.


"Happiness is a warm gun" -John Lennon