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XL5 Offline
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All gas operated guns have to poop somewhere.

Direct Impingement poops where it eats, but it's in a location that at least is convenient to clean up after. All else being equal, the DI system probably will fail to function due to accumulation of poop after fewer rounds fired than an OpRod (gas piston) system.

Typically you have to remove the OR gun's handguards to clean up its poop, which is more involved than breaking down the DI gun to access its breech. But that's an action that typically is needed far less frequently than cleaning the poop from a DI gun. I haven't heard a credible real-world field report on them yet but there are a couple of piston ARs and piston conversions for ARs that advertise they are "self-cleaning."

The bolt in a DI gun gets much hotter in operation than the bolt in an OR gun, too hot to handle, which can be a deal-breaker if for some reason you might need to do emergency maintenance on the bolt (probably not very likely).

The OR system necessarily puts reciprocating mass outside the centerline of the bore, which potentially can negatively impact accuracy.

The OR system has additional parts, additional weight, additional complexity, additional manufacturing costs and additional potential single points of failure.

The OR system also will spray hot poop over whatever happens to be near the gas block when it releases the gas. This might be you hands or gloves or whatever you have hanging on your accessory rails. In the real world, the OR gun's hot poop has been known to overheat handguards.

OR platforms are fussier than DI about gas port tuning if you try to run them suppressed.

If you've heard the nightmare stories and have qualms about the DI platform's reliability, check out this video. It's an M-4, being fired full auto as fast as the operator can change mags:

[video:yahoo]http://www.youtube.com/watch?v=Kzfm4pYhIyY[/video]

At around 400 shots fired, the handguard begins to catch fire. At about 420, one round cooks off. Except for that one cook-off (and the bit about catching fire), the carbine functions normally until its gas tube melts after firing 810 rounds (27x30) in just over four minutes. That's about 190 RPM in a platform with a recommended sustained rate of fire of 12-15 RPM.

Originally Posted by tex_n_cal
I think Stoner pretty well knew what he was doing, when he went to DI. You obviously avoid the piston rattling next to the barrel.

Stoner wasn't married to DI. He built the Armalite AR-18 as a piston-operated advancement on the AR-16.

EDIT:
If my media tag for the video isn't working, it's here.

Last edited by XL5; 02/16/12.

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I wonder how much him selling the rights to the M-16 and it's DI operating system to Colt, had to do with the divorce???

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Nice video.


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Originally Posted by XL5
The bolt in a DI gun gets much hotter in operation than the bolt in an OR gun, too hot to handle, which can be a deal-breaker if for some reason you might need to do emergency maintenance on the bolt (probably not very likely).

Originally Posted by tex_n_cal
I think Stoner pretty well knew what he was doing, when he went to DI. You obviously avoid the piston rattling next to the barrel.

Stoner wasn't married to DI. He built the Armalite AR-18 as a piston-operated advancement on the AR-16.

EDIT:
If my media tag for the video isn't working, it's here.


I have pulled the BCG from my DI AR after some pretty long strings of fire and it was never too hot to handle while the barrel would blister skin.

The video shows how well the DI AR works and also shows how poorly most in the firearms industry shoot. As the video goes you can actually see the shooter improve his reloads and become more efficient at keeping the gun running.

I am always amazed at how well designed the ergos are on the AR-15 and it seems possible (based on the AR-18) that Stoner got somewhat lucky with the AR-10 and AR-15 in this respect.

This really is why all the other pretenders like the SCAR have such an uphill battle in the Carbine Improvement program. If the contenders keep the inline recoil then it is just another AR and if they try and drop the stock to look different then the gun will never shoot with the AR in the hands of someone who has the slightest clue.


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We used to practice rattle battle as a team quite a bit, and I did it at home because I wanted to be proficient.

600 yards could get upwards of 40 plus hits on a silhouette(with irons) in 50 seconds from prone. That of course included 1-2 mag changes.

I'd shoot that time and again. I still never had any melting or fire issues etc... which confirms a lot of what John says here. Still no reason to go piston.


We can keep Larry Root and all his idiotic blabber and user names on here, but we can't get Ralph back..... Whiskey Tango Foxtrot, over....
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Nice video. I wonder how much longer if any the gas tube would have lasted in a rifle length?


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I am impressed with the input here & thankful.


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http://www.thefirearmblog.com/blog/2010/06/09/a-clean-wouldnt-hurt/

Pictures of an DI AR-15 after 16,000 rounds of Wolfe ammo without cleaning, just lube every 1000 rounds. May be dirty, but it still fired.


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Wonder what lubricant he was using?


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Originally Posted by Reloder28
I am impressed with the input here & thankful.


Reloader,

I have been very fortunate to have been given the opportunity by Uncle Sam to be cross trained as an armorer on a whole host of weapons systems, including the M4/M16 series, as well as be the guy in the field carrying it.

I can tell you from spending many hours inside of many defense manufacturers factories acting like a sponge, that I have zero problem carrying a Colt M4 into battle,. The DI system M4/M16 series has served me well in some pretty lousy places, in some pretty austere conditions and has never let me down.


THE CHAIR IS AGAINST THE WALL.

The Tikka T3 in .308 Winchester is the Glock 19 of the rifle world.

The website is up and running!

www.lostriverammocompany.com

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Ya, I may have a deal on a DD m4 v7, but still wonder to just get another colt.


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Granted it's not that evil steel cased stuff but EAG Tactical has a Bravo Company AR that goes by the nom de guerre 'filthy 14' they use in their classes that has been cleaned once in more than 40,000 rounds fired. S.W.A.T. magazine reported on it about a year and a half ago when the round count was 31,165. It has had two or three parts replaced due to breaking/melting but there was a post at ar15.com a couple of weeks ago that said the up-to-date count was 42,770.

EDIT:
That post at AR15.com was wrong. There's a post from Pat Rogers hisself at lightfighter made last July that says it was up to 43,345.

Last edited by XL5; 02/19/12.

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No, no way in hell a non piston gun could run that long. DI from what I've heard, the guns just actually DIE around 10,000 rounds IF they get that far before being so jammed up it would take a torch to cut em apart...

Damn piston guys try anything to fix whats not broken.....


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Rost, you can take whatever Pat Rogers says to the bank.

That round count doesn't involve no lube, it just doesn't involve detailed cleaning.

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I was being a smart azz..... DI has worked that fine for years and years. I"ve got maybe close to 10 new barrels on some of my guns... never ran into a failure, jam etc... which amazes me. Keep em somewhat clean, IE not letting the lube get gummy in the upper, and keep em lubed and they seem to want to run forever.

Which is why I ask... WTF is about gas pistons that folks feel the need?

We had a guy shoot competition highpower one year, he was a high master shooter, took his service gun, shot it ALL year without cleaning the barrel. Wiped the carrier and lubed that every month. He usually shot 12 months of the year. Usually shot 2 matches a weekend if he could find them. Thats typically meaning without any practice and such, and not counting high round count big matches, he was shooting probably on average of give or take, 800 rounds a month, probably closer to 1000 if I wanted to bet.... no issues either.


We can keep Larry Root and all his idiotic blabber and user names on here, but we can't get Ralph back..... Whiskey Tango Foxtrot, over....
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It's common knowledge on the Internet that DI guns fail 90 %of the time....

So many experts, so little knowledge


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It is funny how things change over time.

The piston AR in the world of real high speed low drag was intended to make Short Barreled Rifles (SBRs) with suppressors reliable before we understood how to make SBRs with Suppressors reliable with the DI system.

Now days the guys in the know understand how to make the DI system work better than any piston in the first 2000 rounds or so without any cleaning or maintenance.

Give me a shovel and some nice dirt or sand and I can stop a piston gun sooner than a well built DI gun in the first 2000 rounds from a good cleaning and lubing.

After 2000 rounds and no cleaning then the silly piston might have an advantage.

The overpressure of the DI system will blow sand and crap out of the action long before the carbon build up will be a problem.





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Originally Posted by JohnBurns
It is funny how things change over time.

The piston AR in the world of real high speed low drag was intended to make Short Barreled Rifles (SBRs) with suppressors reliable before we understood how to make SBRs with Suppressors reliable with the DI system.

Now days the guys in the know understand how to make the DI system work better than any piston in the first 2000 rounds or so without any cleaning or maintenance.

Larry Vickers was an early proponent of the piston upper, even he has poste on his site that it probably only is off benefit to someone who has to be able to do sustained full auto fire.

We has 11.5in Bushmasters in Iraq in 05 that gave problems initially and Bushmaster got us different buffers and buffer springs and the guns ran great after that.

Give me a shovel and some nice dirt or sand and I can stop a piston gun sooner than a well built DI gun in the first 2000 rounds from a good cleaning and lubing.

After 2000 rounds and no cleaning then the silly piston might have an advantage.

The overpressure of the DI system will blow sand and crap out of the action long before the carbon build up will be a problem.





We had 11.5in Bushmasters in Iraq in 05 that had issues at first. Bushmaster got us different springs and buffers and they ran great after that.

Larry Vickers used to be pro-piston. Now he says they likely are only beneficial for sustained full auto fire.

Last edited by Take_a_knee; 02/20/12. Reason: spellin'
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I've used DI M16's and M4's in just about every environment from Arctic to Desert to Jungle and never found myself wishing I had a gas piston system. DI works just fine.


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Maybe I am too nice to my guns, I have never got sand or dirt in them, only some rain water sometimes, they never fail but now I know I need to buy a mini 14 because it has a piston and will be more reliable.


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