Anyone know who sells the conversion from direct gas to the piston.
Kurts Kustom Firearms is working on a conversion kit. Look over in the industry forums.
I'm curious about this too. I went to the Industry Forum and KKF's website and I didn't see anything there either. Links?
Frank DeSoma of POF-USA is about to release a gas piston upper (offical release date is December 3rd or 4th, I can't remember off the top of my head). I've pasted below a review he sent me a few weeks ago. Although I did not end up going with his upper because I didn't need the rail system and wanted a 16" barrel rather than the 14.5" his build has, it appears to be a well thought-out and constructed device. The final price I believe is $975 and that is with sights, a rail system, bolt group, and charging handle, so it's not that much more expensive than a similarly equipped direct gas setup. Compared to some other piston systems out there costing in excess of $1500, his is a bargin.
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 restr!
oom 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?
There is the link to the discussion thread on his website