Direct Impingement or Piston Drive?

[roostercogburn98]

Working it over in my brain. Came here to seek opinions/experiences. Current setup is SA adjustable gas block, but I have an SA piston kit sitting around. What would be the benefit/downfalls of each in an SPR type rifle. I can think of a couple such as cleaner/cooler operating. Gun will run suppressed most of the time, and may do some night shooting with PVS14s and a laser so gas cloud interference is a concern.
Would piston leave me in a bad spot at night with the gas venting?

Gun setup is: mega upper and lower, Triggertech trigger, 18 inch Bartlein 1:7.7 SS barrel. Gun shoots good as is, so I hate to change things and start over getting the gas system set up BUT if the benefits outweigh the downfalls, I’m good with doing a swap.

 

[longshot2000]

I like AR platforms that I work with to be simple. DI is the way to go, unless you are using someone else's fantastic piston gun, like Barrett or LMT. Piston would be something I would graduate into if you are new to AR gas guns. There is a very small (less than 1%) market penetration for piston guns, but the guys who do them well... well, do them well. I would not use a retro fit kit.

 

[roostercogburn98]

I like AR platforms that I work with to be simple. DI is the way to go, unless you are using someone else's fantastic piston gun, like Barrett or LMT. Piston would be something I would graduate into if you are new to AR gas guns. There is a very small (less than 1%) market penetration for piston guns, but the guys who do them well... well, do them well. I would not use a retro fit kit.

I’m generally in that mindset of if it’s not broke, don’t fix it. The only other piston gun I have at the moment is a Scar16. I had a sig556 long time ago as well. I enjoyed the way both shoot, but as you said, they are built that way. I’ve never messed with a retrofit kit, so the reason for the thread. I guess I should also mention that the bolt was headspaced to the barrel in a WOA competition barrel extension so changing would require a new carrier. Usually not an issue if the carrier fits upper good. The bolt abd carrier are both Seekins, so I hate to change good components as well. I know SA makes good stuff, so not a knock on them either.

 

[KYAggie]

I have a SA piston kit I put on a 10.5” SBR I put together from parts. I did not retro fit an existing gun, but it’s not hard to do and I can’t imagine it would negatively affect the way it shoots. I like mine a lot and usually run it suppressed; haven’t had any issues with it. I have not run it with night vision, so I can’t speak to that.

It would be easy to swap and if you didn’t like it, swap back. I would go for it.

 

[ut755ln]

Working it over in my brain. Came here to seek opinions/experiences. Current setup is SA adjustable gas block, but I have an SA piston kit sitting around. What would be the benefit/downfalls of each in an SPR type rifle. I can think of a couple such as cleaner/cooler operating. Gun will run suppressed most of the time, and may do some night shooting with PVS14s and a laser so gas cloud interference is a concern.
Would piston leave me in a bad spot at night with the gas venting?

Gun setup is: mega upper and lower, Triggertech trigger, 18 inch Bartlein 1:7.7 SS barrel. Gun shoots good as is, so I hate to change things and start over getting the gas system set up BUT if the benefits outweigh the downfalls, I’m good with doing a swap.

I am not giving you a snarky answer, I am just going to say it. What we call a DI gun is a piston system. It is just a different piston setup than a short or long stroke. Tim on the Military Arms Channel has done a couple of videos on it but it terms of failure rates when systems start to break down and need to be replaced, DI>Long Stroke>Short Stroke.

I have a PWS Mod 2 Mk111 and it is far and away my favorite rifle to shoot suppressed. I adjust the gas block to the second setting and it shoots softer than any of my DI ARs. It is also the cleanest in the sense that it vents the gas up front. I almost never need to do anything other than blow a little bit of carbon off the bolt. I have something like 2k rounds through it so far without any problems, so far it has worked flawlessly.

 

[alamo5000]

I got advice from a very knowledgeable and well known person when I was first getting into ARs. It was the best advice I have ever gotten regarding firearms.

Summarizing the advice:

Go with a gas setup. Piston might be nice but they tend to all have proprietary parts involved. If something goes down, including the companies that make those proprietary systems you will be screwed.

 

[Doom]

Go with a gas setup. Piston might be nice but they tend to all have proprietary parts involved. If something goes down, including the companies that make those proprietary systems you will be screwed.

To this point, with the 2020 Remington bankruptcy we recently went through a period where spare/replacement parts were unattainable. You could not find a 700 extractor anywhere.

The DI system has been in use on the AR platform for over 55 years and its benefits and shortcomings are lwell documented. Personally I wouldn’t change unless I found that the DI system is an actual problem.

 

[KYAggie]

Go with a gas setup. Piston might be nice but they tend to all have proprietary parts involved. If something goes down, including the companies that make those proprietary systems you will be screwed.

This is all true, especially for a gun you would grab if the world ended.

However, having no idea when that might come about and if it will even be in our lifetime, given your stated current useage, the fact SA has been around a while, has a good reputation, and conversion back to DI is easy would all tip the scales towards running your piston set up. You have it, you might as well run it and see what it does for you on a one way range.

If you were going to use it as a primary weapon on a two way range, it’s hard to beat the proven DI system.

This makes me think of all the mall crawler 4x4’s I see that have never been offroad. They are set up with E rated over sized mud tires that have terrible on road wet and snow traction, they ride rough, the are noisey, and they decrease the gas mileage by a lot, but they look cool. The owners would be better off with a two sizes smaller P metric AT given 100% of their useage is on road.

If 100% of your useage is a one way range, give the piston a try. You can always swap back in short order.

 

[GUNNER10]

I've shot LMT's since the mid 2000's and never had any issues shooting suppressed so I have long had a bias towards DI's but I picked up an lmt 12.5 piston set and it's really good. So good that I have reevaluated my position on piston guns. I think we are at the point where as long as a manufacture has their stuff together you can get a damn good gun from them.

 

[roostercogburn98]

Thanks for the replies so far by everyone. My instinct just says stay DI and run it like it likes to be run. It’s not a duty rifle, strictly a range toy that might shoot something at night once or twice. It shoots exceptionally well as is, so I’m inclined to leave it for now. Seems like a pretty fairly split crowd on the subject though. Maybe I’ll try the piston on and SBR 300BO in the near future since I have two different length pushrods with the kit.

 

[KYAggie]

Maybe I’ll try the piston on and SBR 300BO in the near future since I have two different length pushrods with the kit.

I would suggest calling SA before you try that to see if there’s enough port pressure with a suppressed 300BO runnings subs before trying that with their piston kit; it may not work there may not be enough port pressure.

 

[Steel head]

DI

 

[roostercogburn98]

I would suggest calling SA before you try that to see if there’s enough port pressure with a suppressed 300BO runnings subs before trying that with their piston kit; it may not work there may not be enough port pressure.

Shoot mostly 110s I’m the BO now days. The heavy stuff is fun and quiet, but the 110s give some more room to play with.

 

[candyx]

The reason Mikhail Kalashnikov went with a piston system as he stated there wasn't any reason to reinvent the wheel. They tell you DI stands for direct impingement but in reality its Dirty Impingement.......

 

[troupe]

DI is proven, but piston is nice suppressed, cleaner and cooler.

 

[alamo5000]

I posted earlier in this thread, but to make it clear I'm not at all anti piston. Once I get my staple of DI rifles then I would definitely entertain a piston gun. If I had just one AR it would not be a piston gun.

At present I have 4 ARs built from top shelf stuff. Up the road a bit I might entertain something else but even then I would like to maintain the ability to fix/repair/or replace stuff.

The idea of having a Lego gun (or guns) is attractive, but introducing a variable would throw a monkey wrench in my current plans.

It's not just the gas system, but the bolt carrier group, and who knows what else (depending on what setup it is) that I would want to build redundancy for.

I'm not to that stage yet though.

 

[alamo5000]

To this point, with the 2020 Remington bankruptcy we recently went through a period where spare/replacement parts were unattainable. You could not find a 700 extractor anywhere.

The DI system has been in use on the AR platform for over 55 years and its benefits and shortcomings are lwell documented. Personally I wouldn’t change unless I found that the DI system is an actual problem.

If there ever is an event of some type that interrupts the global supply chain or something of that sort it's certainly nice knowing that I can swap parts or cannibalize parts from other things I own.

It doesn't need to be some end of the world scenario. Anything could happen...

 

[candyx]

If there ever is an event of some type that interrupts the global supply chain or something of that sort it's certainly nice knowing that I can swap parts or cannibalize parts from other things I own.

It doesn't need to be some end of the world scenario. Anything could happen...

Plenty of parts and weapons will be available if you win your skirmishes roaming the countryside when this thing shits the bed.

 

[alamo5000]

Plenty of parts and weapons will be available if you win your skirmishes roaming the countryside when this thing shits the bed.

I don't doubt it a bit.

That said, my point is if you get caught up in some proprietary piston setup you better hope that your neighbor owns a gun with the exact same type and dimensions of piston wigit that you need to make things run again.

If things go south you have to hope somebody else has the same tastes in piston parts as you do.

 

[White Death]

I have both LMT and barrett piston rifles and prefer them over DI. They run great even with minimal lubrication and will shoot any kind of cheap, dirty ammo with no issue.

 

[candyx]

I don't doubt it a bit.

That said, my point is if you get caught up in some proprietary piston setup you better hope that your neighbor owns a gun with the exact same type and dimensions of piston wigit that you need to make things run again.

If things go south you have to hope somebody else has the same tastes in piston parts as you do.

Any port in a storm , I have no problem switching to a DI that was never fired and only dropped once.

 

[KYAggie]

That said, my point is if you get caught up in some proprietary piston setup you better hope that your neighbor owns a gun with the exact same type and dimensions of piston wigit that you need to make things run again.

If things go south you have to hope somebody else has the same tastes in piston parts as you do.

Actually, all you need is a gas block, a gas tube, and a standard bolt carrier and you’re back in business with a DI system; that is IF you have problems with your piston set up.

 

[GUNNER10]

As somebody who owns both, the parade of imaginary horrible's, in regard to spare parts in a resident evil/book of eli type scenario is a little silly. Spare parts are easier to come by in DI, but its not exactly difficult to get spare parts for a piston set up its thats your cup of tea. I would recommend, the everyone, regardless if you shoot at DI or Piston, spend the money and get yourself a field repair/spare parts kits/tools/carbon scarper so if something weird comes up, it can be addressed .

 

[Milf Dots]

By a decisive margin and from the start the shooting world chose to describe the AR18 technology as a piston driven design and the AR15 as Di/Direct Impingement or Direct Gas design.

The logic behind the naming convention is based on the fact that in the AR18 there is a piston/piston rod moving the bolt to cycle the action, while in the AR15 dirty gases flow through a thin walled gas tube to move the bolt. There is no piston in a Di/Dg AR- the bolt isn't a piston in either design.

Even in an AK pattern rifle the piston rod is the piston, the bolt isn't the piston.

 

[GUNNER10]

Something interesting about the AR18 system that has emerged as the preferred operation system of modern shoulder fire weapons is that each manufacture does implements it their own way and and there is even less parts commonality between manufactures that you will find in a Piston or DI AR.

Be it Sig, FN, HK, Berretta, CZ, Styer, or anybody else the trend is moving towards proprietary systems on outside of maybe the AR or AK, one should not really count on parts commonality moving forward.

 

[Milf Dots]

The OP already owns the piston kit, yet the "no" replies give the false impression he asked about acquiring Piston vs Di, LOL! Hence my above reply to address some of that.

IMHO, if Stoner and colleagues had introduced the arguably then more reliable piston AR18 to the Army first, we'd all own AR18 clones and not AR15 clones! And nobody would be looking to move from piston to the much dirtier operating Di design.

When piston AR18 clone rifle manufacturers really started to heavily market the AR18 design, virtually 100 percent of the U.S. AR market owned Di models. So the huge Di AR parts and accessories industry simply chose to shut down the potential change to their business and product lines by discrediting the piston design and its advocates...

...The Di AR industry's response compelled many of the existing AR owners with an appeal to 'defend' the AR as if it were under some sort of attack. Most people new to ARs who inquired about Piston vs Di were almost always given the exact same talking points by existing Di owners who again made up almost 100 percent of our existing AR market, so it's no surprise that Piston ARs account for such a low percentage of the market.

In an interesting twist, the market segment least likely on average to properly clean and maintain guns, and most likely on average to benefit from the much cleaner running piston guns, are NEW shooters. But because the piston AR18 clone makers priced their offerings so much higher- instead of within, say, a hundred bucks of a similarly equipped Di gun, it allowed the Di fans and gun makers to use the erroneous argument that "new shooters would be better off with Di and that piston was for serious shooters- oh and you'll save money on a Di gun, too".

I'd really like to see piston AR18 clone manufacturers drop their pricing to within a hundred bucks of similarly equipped Di models, but I wouldn't be surprised if they've done the math and decided that selling fewer piston rifles at a much better margin is preferable to dropping prices to sell more. Many of the best piston gun makers are also now making some of the best Di guns, so maybe they've found the best for them business model of manufacturing both piston and Di.

IMHO one couldn't go wrong with a Piston or Di gun from Barrett, LMT, or LWRC.

 

[Milf Dots]

Something interesting about the AR18 system that has emerged as the preferred operation system of modern shoulder fire weapons is that each manufacture does implements it their own way and and there is even less parts commonality between manufactures that you will find in a Piston or DI AR.

Be it Sig, FN, HK, Berretta, CZ, Styer, or anybody else the trend is moving towards proprietary systems on outside of maybe the AR or AK, one should not really count on parts commonality moving forward.

Good point that appears to be supported by the USMC's wide adoption of the HK m27/416. The huge successes of both the FN SCAR and Sig MCX. The Army's NGSW contenders. I think there's some lineage from the AR18 licensed for the Daewoo rifles.

 

[Milf Dots]

DI is proven, but piston is nice suppressed, cleaner and cooler.

Yeah, the OP did mention running suppressed and NODs, and even with a suppressor a piston gun does put more of the gas away from the face/NODs than a Di gun.

 

[GUNNER10]

While the NGSW is more of a evaluation on feasibility more so than serious consideration, its would be somewhat interesting to see the Sig be adopted at some point. as it would be similar to what happened with the Mag58/240 and the M60 when first evaluated where we really ended up passing on a better design for internal reasons but ended up at that point decades later.

 

[GUNNER10]

Its interesting that you bring up that AR owners were led to defend the platform in light of new developments and I would considering myself being in that category for quite some time. Today, I think that pistons are good, and the way forward, While they may run cleaner, I don't think they are offer any game changers over a well built DI , and for practical use and in some cases, the higher end DI guns may actually be better guns in some regards, such as smoothness, and durability/robustness(LMT EBCG/KAC E3).

I think the the piston side of the house has done great work on coatings that has filtered back to the DI side. I think that Piston AR's/Modernized AR18's absolutely have the same ability to be refined to the point of say a Kac SR15. I would love to see an enhanced bolt make its way into an AR18 design as right now, AR18 type bolts do not offer any increase in service life when firing 855A1 as the failures originate at the lugs.

I think that a good DI AR right now, is an damn good weapon that has really benefited from from the last two decades of post 9/11/GWOT development From the Mk18 program to the SPR/Recce Program, to the M110 program, the DI system has had billions of dollars poured into it and its end results shows. In addition to DoD money, the US gun industry has also spent a ton of money making the AR better as well.

I think the original program objectives of the scar was and is still incredible, a lightweight, modular replacement for the M4/SPR/m14/what ever. The problem is that when the AR industry was going balls out trying and succeeding in reinventing the wheel 2 percent at a time, FN just dumped their rifle on the market at 3k and walked away, Todays scar is basically no different that it was when it went down range in the mid 2000's. In their large frame variant they need a Mk20 to do the accuracy thing and a mk17 to do the battle rifle/carbine thing. After two decades their is zero reason that they can not achieve this from a single universal large frame receiver. This is not a specific FN issue, HK is in the same boat, they developed the pinnacle of SMG's in the 70's and walked away. no need for a better trigger/ergonomic trigger pack, bolt hold open/release. Just done sir, done.

Despite the short comings of the DI system, its hard to find a DI AR with a bad trigger, Most AR18's triggers are poop. San Swiss made a solid trigger, although it is an AK trigger, but outside of Switzerland, I don't think this is a concept that they understand. Hell the triggers in our Russian SVD's and VSS's would blow most euro triggers out of the water,

At this point I think that the refinement of the AR18 lies with Sig and Brownels via the aftermarket. The sig is absurdly overpriced, but is marketed towards the US where most weapons development takes place, Brownels is the most economical option that is targeted towards the same market. I think the rest of euro AR18 are solid guns but basically can be summarized as basically what you see is what you get.

 

[GUNNER10]

Good point that appears to be supported by the USMC's wide adoption of the HK m27/416. The huge successes of both the FN SCAR and Sig MCX. The Army's NGSW contenders. I think there's some lineage from the AR18 licensed for the Daewoo rifles.

The Funny thing is that outside of line units, the M4 is still fielded. What is also entertaining is that their the MARSOC guys appear to went down the URGI route vs the in house M27. While the 416 is a good gun, especially the A5, the Marines, bought the heaviest variant they could find in 2006 to make an IAR, and being lazy, they said, hey, this is now our infantry service rifle. congrats, every rifleman now has a 2006 IAR. Good job guys.

Oddly enough, I was 2/7 when we did the initial evaluation back in 2000 with the g36, Colt LMG upper and Ultimax 100 i think.

Weapons procurement and evaluation has been a complete and utter shit show for at least the past two decades.


Sigh....

 

[roostercogburn98]

Yeah, the OP did mention running suppressed and NODs, and even with a suppressor a piston gun does put more of the gas away from the face/NODs than a Di gun.

Think I may swap it for a few rounds just to see how it plays. If I like it, I may just swap the SA adjustable gb over to the sbr BO. May just be a win/win, or could be a lose/lose. Only time and ammo will tell at this point.

 

[Milf Dots]

I've learned some stuff in this thread. Good stuff.

 

[schmi015]

Under 12 inch barrel gas piston, over 12 inches gas impingement.

 

[TheHorta]

All of my guns are pissed on.

 

[Milf Dots]

All of my guns are pissed on.

Best way to cool them down.

 

[roostercogburn98]

All of my guns are pissed on.

Cause you own moa trash in 6.5

 

[ansel]

At least one contender competing for the new squad rifle contract is piston driven (sig) ....Not sure about the Textron offering. Also there are at least several reports of the M4 jamming in intense fire fights during Afghanistan combat. The articles state overheating of the BCG resulting from extended high rate of fire during overrun attack episodes (just when you need it most). Google it up......

 

[Milf Dots]

At least one contender competing for the new squad rifle contract is piston driven (sig) ....Not sure about the Textron offering. Also there are at least several reports of the M4 jamming in intense fire fights during Afghanistan combat. The articles state overheating of the BCG resulting from extended high rate of fire during overrun attack episodes (just when you need it most). Google it up......

All three (now down to two) offerings are piston driven.