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Pulled this from ar15.com. Piston ARs fixed the DI issues, right?


"With the direct gas impingement system, when gas goes through the gas tube and into the bolt carrier via the snorkel, the gas pressure forces the bolt FORWARD, holding it
securely in place, locked in the barrel extension, while the pressure behind the gas rings forces the bolt carrier backwards. The bolt is pushed forwards by gas, and the bolt
carrier is pushed backwards by gas. The cam action rotates the bolt out of battery and the inertia imparted to the bolt carrier pulls the bolt out of the barrel extension.
The pressure applied on the carrier is almost entirely aligned with the direction of travel of the carrier. The carrier gets pushed straight back, excluding some relatively
minor torqueing forces applied via the gas stream through the snorkel. The carrier action is very linear, without any significant lateral forces applied to the upper receiver
or carrier.


With a gas piston system, there is no supplemental pressure burst against the rear of the bolt to hold it securely in battery while the pressure curve drops off, which may or
may not be significant, but more importantly, the driving impulse on the bolt carrier is off -axis by a respectable amount, well outside the outer diameter of the carrier, which
makes the carrier torque toward the bottom of the upper receiver, causing rapid premature wear, and in some cases, a minor misalignment between the upper receiver bore
and the buffer tube bore can become a point at which the bolt, being driven back with a considerable downward torque force on its rear edge, snags and takes some damage
with every shot. Bolt carriers that are used in piston guns should have beefed up bearing surfaces on the lower section of them and the lower rear of the carrier should be
given a good, well polished ramp cut.

Knight also says that bolt breakage is considerably higher in piston ARs than in direct impingment ARs. The reason is apparently due to the very sudden impact delivered to
the bolt and carrier by the gas piston when driven by the gas stream, compared to a more moderate push given to those parts by a direct impingement gas system which
has a definite pressure curve profile to it, much different from the virtually "square wave" pressure curve delivered via a piston system. "
 

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Hmmm....

I've had no problems with my LMT piston upper on my AR... ;D

Maybe because it was designed as a piston upper, unlike some that are conversions? ???
 

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This will be debated forever. I still prefer my LWRC upper over DI. I can blow through 500 rounds of crap ammo and still have a BCG covered in lube and very little grit, which means not cleaning for 40 minutes
 

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This will be debated forever. I still prefer my LWRC upper over DI. I can blow through 500 rounds of crap ammo and still have a BCG covered in lube and very little grit, which means not cleaning for 40 minutes
Ditto. My LWRCs run perfectly. My DI AR just sits now.

In fact my DI AR is going up for sale shortly to fund another XCR.

Sean
 

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That's an excerpt from the latest issue of Small Arms Review, which features a lengthy interview with Reed Knight, owner of Knight Armament, who has had a long relationship with Eugene Stoner. Knight is a big fan of the Stoner system.

tk
 

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That's an excerpt from the latest issue of Small Arms Review, which features a lengthy interview with Reed Knight, owner of Knight Armament, who has had a long relationship with Eugene Stoner. Knight is a big fan of the Stoner system.

tk
There you have it. Straight from the mouth of someone who does not have Piston-AR in his lineup. DI is a great system if you have time to clean your weapon. I will still take my LWRC and XCR over a DI AR. Don't worry, I am not related to Kalishnikov so I have no pro-piston agenda to push.
 

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Well AR's and AR variants will usually work just fine for regular civilian use with proper care. But if your talking "battle" conditions I would rather take a Piston AR or quality Kalashnikov rifle for reliability without cleaning worry. I'm not saying you don't have to clean them, but my Russian cycles flawlessly without a cleaning in a few thousand rounds, plus the new Russian stuff have chrome lined barrels ect. They aren't as accurate as say a XCR or LWRC or HK 416, but it'll hit a target good enough. I had a DI AR from bushmaster and it worked great, cleaning sucked but still flawlessly operated. But I wouldn't take it into battle unless it was my only choice.
 

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That's an excerpt from the latest issue of Small Arms Review, which features a lengthy interview with Reed Knight, owner of Knight Armament, who has had a long relationship with Eugene Stoner. Knight is a big fan of the Stoner system.

tk
There you have it. Straight from the mouth of someone who does not have Piston-AR in his lineup. DI is a great system if you have time to clean your weapon. I will still take my LWRC and XCR over a DI AR. Don't worry, I am not related to Kalishnikov so I have no pro-piston agenda to push.
Beware of shills. This hobby is full of em. For months there was a guy on another forum who was a hack for KAC gear. He was always posting glorious range reports and how great they are. Turns out he is on their payroll.

This is the sorta crap people looking for information need to beware of, especially in threads about DI and piston guns.
 

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I am by no means an expert on this, but the folks at Adams Arms have a spring loaded bolt now. That spring puts forward pressure on the bolt and acts as an initial buffer to start the bolt rearward to avoid the slamming effect. I believe HK has something to this effect as well. AA also has changed their one piece bolt and bevelled it near the back and bottom side. They've been working on getting it as close to right as possible.

I have two of the systems. My first one built by Stag works perfect. My second one wasn't quite installed properly. The piston was banging against the bolt and bent the key. After a new key and proper fitting (no slack). Everything is perfect. Since mine are lefties, I can't get one of the one piece bolt carriers. They only have those for righties.
 
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