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Author Topic: Gas Piston vs Direct Impingement AR-15 system.  (Read 17147 times)
G22Cesar
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« on: May 08, 2011, 11:58:05 AM »

So stirring the pot I may but as I get close to finally being able to shoot my first AR (Thanks Bulldog for all the help) I keep doing my homework an learning as much as I can about my rifle.

So I am here to ask all the vet's and gents that know WAY more about AR's then I do what they think about this heated discussion. I'm trying to think back and maybe on the old site this topic was brought up but as I sit here and watch my Brisket smoke away the thought Creep'ed into my head.

So hope everyone is enjoying the sunday.

Oh and Pic's will be posted of the AR once Bulldog and I hit the range.

Cheers.

--Cesar
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bulldog7926
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« Reply #1 on: May 08, 2011, 02:17:20 PM »

there really is no discussion imo. the m16/ar platform was designed as a di system. it works VERY well when used with quality parts (ie milspec).
 
there is the cleanliness issue. di is dirtier, but Filthy 14 shows that filth does very little in the way of impeding weapon reliability or function. There have even been tests on di systems that used NO lube until the point of failure to function. If I remember they went about 7-12000 rounds until failing to reliably close the bolt. Ill hunt the tests down if need be.

Gas piston drop-ins and even ones made for the ar platform still have problems since the weapon was never designed for this upgrade. Ive heard of carrier tilt being one of the cited problems.

Pistons do have the advantage to tune the recoil so you can add suppressors . How many folks will really benefit from that? A supersonic round with a suppressor is kinda silly imo.

Now there are reliable weapons that are built around a piston design and work very well. However the price tag reflects this.

In short, gas piston guns that are designed to use the system work and work well.
Di guns built to spec work and work well for less money and reliability is as good as piston guns if not better.

Guns not built to the spec whether di or piston will not stand up to others that are.

My bitch about piston guns is that parts are proprietary. Even cheap di guns have interchangeable parts that can be substituted if need be.

My 2 cents, fwiw.
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kfeltenberger
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« Reply #2 on: May 08, 2011, 05:12:11 PM »

there really is no discussion imo. the m16/ar platform was designed as a di system. it works VERY well when used with quality parts (ie milspec).
 
there is the cleanliness issue. di is dirtier, but Filthy 14 shows that filth does very little in the way of impeding weapon reliability or function. There have even been tests on di systems that used NO lube until the point of failure to function. If I remember they went about 7-12000 rounds until failing to reliably close the bolt. Ill hunt the tests down if need be.

Im not so sure about the round count, I thought it was a bit lower, but be that as it may, a DI system not only adds carbon to the upper and lower receiver area, but also adds heat.  Heats the killer, in that it bakes the carbon onto the parts.  Properly maintained, its a good system and it works as its designed to work.  I wouldnt feel like I was handicapped if I had one.

Gas piston drop-ins and even ones made for the ar platform still have problems since the weapon was never designed for this upgrade. Ive heard of carrier tilt being one of the cited problems.

Pistons do have the advantage to tune the recoil so you can add suppressors . How many folks will really benefit from that? A supersonic round with a suppressor is kinda silly imo.

Suppressors dont muffle the crack of the bullet, but what they do is mask the muzzle blast.  The muzzle blast is what gives you a good idea the direction the shot came from and that confusion on the part of the targets is beyond value if theyre going to shoot back.

Some of the retrofit systems are good, some not so good.  I think its telling that none of them have really been adopted in any large numbers by LE or .mil. 

Now there are reliable weapons that are built around a piston design and work very well. However the price tag reflects this.

In short, gas piston guns that are designed to use the system work and work well.

Absolutely.  Gas piston guns in an AR format are out there, and given my choice, thats the flavor of AR that Id own.  One thing thats a major stumbling block is that there are numerous competing designs and none of them are in widespread use, other than perhaps the LWRCI design (several government contracts).  YesI know that HK has a wunderwaffen out there, but there are some issues with the gun that absolutely preclude it from any serious consideration as anything more than range toy.
Di guns built to spec work and work well for less money and reliability is as good as piston guns if not better.

Guns not built to the spec whether di or piston will not stand up to others that are.

My bitch about piston guns is that parts are proprietary. Even cheap di guns have interchangeable parts that can be substituted if need be.

My 2 cents, fwiw.

At this time, if youre looking for a weapon as your go to gun when the chips fall from the sky, DI is probably the way to go unless you have enough excess cash to buy a large stock of the proprietary spare parts that your rifle uses.  If you have to have a piston driven design, consider biting the bullet and buying either an AUG, MSAR, SCAR, or AK.  I cant in good faith suggest the Bushmaster ACR because it just has too many issues for prime time at this point in time.
 
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G22Cesar
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« Reply #3 on: May 08, 2011, 05:41:51 PM »

@ Kelft I have no plans on changing to a GP system. I appreciate all the info and if I ever do get another Tactical Type Rifle it will probably be a SCAR. I just love that Rifle but the 2000+ price tag always makes me hesitant and I figured I would go all Milspec with my first AR-15 and see how it goes.

I'm sure before Bulldog and I hit the range on Thursday I will put another coat of SLIP on the BCG and let it "bake" per the instructions then WET it up again and finally make it go bang bang.

Super excited for that and keep the info coming if anyone has anymore info on the subject.

Cheers,

Cesar
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bulldog7926
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« Reply #4 on: May 08, 2011, 06:23:45 PM »

did a quick search. here's one that's interesting but not the 7000 i said before. i still need to hunt that down.


http://www.defensereview.com/the-big-m4-myth-fouling-caused-by-the-direct-impingement-gas-system-makes-the-m4-unreliable/
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kfeltenberger
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« Reply #5 on: May 08, 2011, 07:00:04 PM »

did a quick search. here's one that's interesting but not the 7000 i said before. i still need to hunt that down.


http://www.defensereview.com/the-big-m4-myth-fouling-caused-by-the-direct-impingement-gas-system-makes-the-m4-unreliable/


I think that an institutionalized hate for the M-4 has developed in the last ten years based on hearsay, innuendo, and agenda.  The weapon works, and works very well.  I've read articles about the M-4 going back to Mogadishu and rarely if ever were they written by the people pulling the triggers.
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G22Cesar
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« Reply #6 on: May 08, 2011, 08:53:24 PM »

did a quick search. here's one that's interesting but not the 7000 i said before. i still need to hunt that down.


http://www.defensereview.com/the-big-m4-myth-fouling-caused-by-the-direct-impingement-gas-system-makes-the-m4-unreliable/


After reading that I'm pretty happy you steered me into getting the H2 buffer bulldog. All this reading has me more and more excited for Thursday.

--Cesar
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kfeltenberger
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« Reply #7 on: May 09, 2011, 09:55:51 AM »

IMO, provided you have good parts and remember your maintenance schedule, a DI gun will run just fine.  You may need the roll of quarters to feed the "Cuss Jar" when you clean it at the end of the day, but it'll run well.
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Haji
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« Reply #8 on: May 10, 2011, 10:05:35 PM »

Clean it? What's that? No idea what you're talking about. I don't do any real maintenance until I'm somewhere over 1,000 rounds. Then I sometime run a snake through the bore if I remember to, and wipe the bolt, bolt carrier, and anything else that looks like it needs it. give it a good wet dose of SLiP 2000 EWL, put it back together, and take it back to the range. If you're using anything that scrapes on your AR, you're doing it wrong and doing more damage than good.

In terms of piston guns, there's a HUGE difference between the cheap drop in kits and an gun built from the ground up to be a piston gun like the 416 and the LWRC guns. There's a very significant price difference, too. Is it worth the difference? If you shoot a LOT, then yeah, it may be. They generally have a somewhat longer service life. The gas rings (really an o-ring) on a 416 don't need changing for 20,000 rounds. Is it worth the price difference vs. a DI gun? Not on my ammo budget. If you can swing a good one, have at it. Don't expect a commercial spec piston AR (Stag, Bushamster, Ruger, etc) to perform like a duty-quality DI gun, and you can't go wrong.
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RCS
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« Reply #9 on: May 15, 2011, 07:15:47 AM »

I've gotta say, guys.  I may be coming back here more often.  There was a time on here when the only logical response to "gas piston AR" was "you're an asshat."  I'm happy to see this.

Also, I own DI and don't see myself switching at all anytime soon (that is, unless, SCAR 17s come down in price--by about half).  keep your weapon oiled, and it's hard to beat DI.  Piston is a much more maintenance-free system, but it's costly at this time.
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BlackDogExpress
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« Reply #10 on: May 15, 2011, 07:26:36 AM »

To each his own. I own both, and the gas piston guns run exponentially cleaner and cooler than the direct impingement guns. I don't know why so many 'DI guys' take offense to that being said, since a DI AR15 is a great gun as well, but it is not only more sensitive to crud, it creates a lot more. As far as the cost gap the differences are much smaller than they used to be, and getting smaller all the time. As far as the quality of 'cheap drop in kits' goes, I know a bunch of guys shooting them with no problems. There were rumored issues with early kits that did not use one piece carriers, just a push pad replacement for the gas key, but basically everyone has moved away from those now. I'm sure I haven't bought my last DI AR15, but the last one I currently have is about to get an Osprey piston kit because of my experience with GP AR15s. I chose the Osprey for this gun because I don't want to remove the FSB. Five minutes of work and you can throw your carbon scraper away.

As far as proprietary parts go, the bolt carrier is not going to break, and the piston/rod will outlive the barrel, so there is no need for spares on the 'proprietary' parts. All other parts are standard and interchangeable with any DI gun. I also never have to fool with changing gas rings again - they are actually removed in a piston gun, so there's one part that needs regular replacement gone, and taking most of the heat off of the bolt and its internal components extends their life as well.

I can also use a roller cam (Patriot Ordnance Factory) pin in a piston gun without having to remove the gas key and stake on a new one that is relieved for it, and run a bolt spring (Adams Arms) although I guess you could run this part in a DI gun, both optional parts that save some wear in two more places as well.

Here is a picture of the stock Ruger SR556 bolt and carrier parts.


« Last Edit: May 15, 2011, 07:55:21 AM by BlackDogExpress » Logged

Shell Games
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« Reply #11 on: May 15, 2011, 12:03:36 PM »

Quote
  I own both, and the gas piston guns run exponentially cleaner and cooler than the direct impingement guns. I don't know why so many 'DI guys' take offense to that being said, since a DI AR15 is a great gun as well, but it is not only more sensitive to crud, it creates a lot more.   


I think you answered your own question with the "more sensitive" bit. I've yet to see the "crud" (carbon) created by a DI gun have any negative impact on its performance. Saying a DI gun runs dirtier is technically correct... Acting as if it makes any difference other than for unnecessary OCD cleanings is when many "DI guys" will take issue.

BTW- What's a carbon scraper?  Wink
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bulldog7926
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« Reply #12 on: May 15, 2011, 05:34:51 PM »

glad Shell asked cuz what is a carbon scraper? as for cooler, what part are you referring to? i ran 150 rounds through my bcm middie a month ago to see how well the magpul hand guards worked and pulled the bolt out while the barrel was smoking. i held it by the lugs as i've done before to prove a point to my shooting buddie who is on the verge of buying a piston gun. he didn't think you could do this without burning your fingers to the bone. neither the bolt, carrier or upper behind the barrel got hot at all. now the little rivets on the magpul guards burned my ring finger a bit but that's about it.
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BlackDogExpress
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« Reply #13 on: May 15, 2011, 06:21:29 PM »

Check my post in the gun pics thread to see DI and GP ARs side by side. I have no hate for the DI guns,  Wink but guns do fail from being dirty. That's a simple fact. Pretending like cleaning your weapon is an optional endeavor doesn't make it less necessary. Can most military weapons get pretty hot and dirty before they stop running or start to run badly? Yes, but it does happen. The military went looking for a piston system (and found the HK-416) for just that reason. I have seen a trigger group jammed up from caked on carbon fouling breaking loose badly enough to stop a gun from working. The exponential reduction in fouling also means a piston gun will run with a lot less lubrication.

As for cooler, yes I was talking about the upper receiver and everything in it, particularly the bolt carrier and bolt assembly. Run a DI gun and a GP gun side by side and the difference is quickly obvious.

Not everyone will see a cleaner, cooler running weapon as being worth a little extra money, and that's cool as well. The DI platform does offer one advantage. It's a bit cheaper. That's not the deciding factor for me personally, but to each his own. I don't buy the cheapest ammunition either.

Carbon Scraper: http://www.ar15.com/content/products/cleaning/boltCarrierScraper/
Moacks, which includes a purpose designed bolt tail cleaner: http://www.m-guns.com/tool_new.php?product=moacks
Otis scraper kit: http://www.brownells.com/1/1/43018-brass-scraper-tool-set-brass-scraper-set-otis.html
« Last Edit: May 15, 2011, 06:27:28 PM by BlackDogExpress » Logged

bulldog7926
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« Reply #14 on: May 15, 2011, 07:47:08 PM »

well um, ok. i sighted and "broke in" a robinson about 6 weeks ago. this was done using over 500 m855  and about 200 sellier and bellot that was on hand. I noticed no difference in the temp of the upper or the gun in general compared to all the di guns Ive used over the years. I will say that it was less accurate. My stash consists of 2 bravo middies, an lmt and cmmg. Compared to these it did not hold as tight groups no matter what setting was used on the gas block. Recoil also did not seem at all different between settings even though my buddy swears he can feel the difference.

just last week i helped a guy sight and almost break in a di gun with 300 rounds of xm193 black box federal. we opened the rifle when finished to show him what to clean at his request. there was no fouling to speak of. he said" what do i clean?" i just wiped the carrier with one swipe of a towel and said "done".

that's the difference between quality and commercial.

Also, there is a wonderful article out there about a di gun that was used while it was disgustingly filthy. No remark was made that it failed to operate due to dirt. It did fail to run because of extraction spring fatigue and once it broke some lugs off the bolt. At last count this gun has over 40,000 rounds through it and has only been cleaned one time at something like 26,000 rounds or so. So your statement that dirty guns will fail isnt exactly accurate.

I have never used a carbon scraper. I will never use one. I was being facetious.  There is no need if you purchase a quality ar. My lmt has over 2000 rounds through it and I have never had to clean the inside of the carrier or scrape the bolt tail. If you buy low end then you get what you pay for. There are a few manufacturers that are jumping on the gp bandwagon and its quite sad to be sure.  To get any benefit from a gp system the weapon needs to be designed from the ground up and not just thrown together from other folks parts. That bolt carrier you referenced in the pic reminds me of such a company.

As someone said recently,
I think that an institutionalized hate for the M-4 has developed in the last ten years based on hearsay, innuendo, and agenda. The weapon works, and works very well. I've read articles about the M-4 going back to Mogadishu and rarely if ever were they written by the people pulling the triggers.


But heres a link to a rifle that according to you should not work. 

http://www.bravocompanymfg.com/v/vspfiles/assets/images/filthy14_oct10.pdf



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