[noknock1]

I may have a good deal on buying one new M400 Enhanced rifle. Are there any owners on this site with experience with this or any other direct impingement AR style rifle?

The direct impingement is intriguing and conceptual I see how it would be cleaner, but wondering if anyone truly believes direct impingement is superior to the original gas design? Does it stay that much cleaner? I don't see the big deal with cleaning AR's, especially these days since I picked up a couple carbon scraper tools for the bolt and carrier assembly. Although if direct impingement is that efficient, it may make me lazy!

 

[g7777777]

There are varous "piston" guns out there- this is just another one

Of course there are a zillon of the gas tube models

The theory is that the gas tubes have less muzzle jumb and the pistons are more reliable but I dont know about either claim really

More likely to go with the gas tube models do have less felt jump - they are pretty darn reliable after 40 plus years of service behind them

Regards from Iowa

Gene

 

[wireguy]

Guns and Ammo magazine did an extensive torture test using several examples of both kinds. Their tests revealed no practical advantage from either design as compared to the other.

 

[Don Steele]

Thanks for sharing. Looks like a fine rifle. Also looks like a solution in search of a problem for 99.5 % of 5.56 shooters.
That doesn't make it bad...but I doubt I'll trade in my "old-school" gas tube AR to get one.

 

[Sky Buster]

Gas impingement in a AR is a answer for a non-existant problem.

 

[W.R.Buchanan]

Noknock: A Direct Impingement gun is what a normal AR is.

A piston operated gun is what the Sig is. A piston operated gun uses an operating rod to move the bolt, the combustion gasses never get near the breach or action of the gun. Thus they run cleaner and cooler.

The direct impingement guns use the "direct impingement of the gas" on the little nub on top of the bolt to move the bolt carrier, GAs is directed down into the bolt carrier where it pushes the carrier back while keeping the bolt in battery until the carrier moves far enough back to unlock the bolt and then travel back far enought the eject the round and feed a new one.

The chamber inside of the bolt carrier does get dirty and there is carbon build up to deal with on the piston end of the bolt itself. There is a special cleaning tool for this. Frog Lube works better as nothing sticks to it.

Since the combustion gasses are being directed into the bolt carrier the heat associated with that heats the bolt. Also, as soon as the bolt carrier starts to travel back those same gasses vent into the receiver resulting in dirt that would not mormally be there. IE: Garand/ M14, M1 Carbine..

The piston guns will run longer without cleaning than a DI gun, also they will run longer and more reliably in a prolonged gun fight due to not heating up the receiver which is made of aluminum and conducts heat very well. This will eventually show up as malfunctions which must be cleared in a timely manner to avoid getting shot.

That said, DI guns are what are most common by far, and they wouldn't have gotten that way if they didn't provide satisfactory service in a battlefield environment.

You just have to learn how to keep them running, and it ain't that hard.

I hope this clears up any questions you have.

Randy

 

[Brian in Oregon]

<i>"Gas impingement in a AR is a answer for a non-existant problem."</i>

Uh, no, gas piston in an AR is an answer for a non-existent problem.

Further, when you go with a gas piston setup, you are married to it. The gas pistons are proprietary, because there is no milspec standard.

A gas piston might make sense if you are trying to turn an M16 into a squad automatic, but most SAWs have evolved to belt feed, not mag feed.

 

[noknock1]

Thank each of you for the info, I understand how the system works, I am just wondering if in real world experience these rifles run SIGNIFICANTLY cleaner (no pun intended) than the gas rifles that I own?

 

[art g]

The Sig M400 is basically their version of a standard direct impingement AR15 M4. The 500 series Sigs use a proprietary short stroke piston system. If you are looking at a Sig M400 it basically is no different in its operation than any other AR15. I would say that 99% of civilian users will never shoot enough to have the piston drive vs. direct impingement debate matter in any significant way to them. Art G.

 

[noknock1]

Great information, the info that I received made me think that the M400 was a PISTON system, I see that it is the traditional GAS system that I am familiar with... Thanks to everyone for clearing that up.

 

[Shooting Coach]

Knowledgeable folks in the industry will tell you that IF you run a can or SBR, the piston driven gun may be better.

Other than that, the piston driven gun has numerous disadvantages.

 

[shadow]

I have a Sig M-400 and the little rifle has been an exceptional performer for me. Never a malfunction and accuracy is better than I can hold it. The rifle has digested any ammo I have fed it with never a problem. It shoots the heavier bullets with a bit more accuracy than most ARs, this must be because of the 1-7 twist.

 

[oz]

the gas piston sounds good but I wonder what effects the piston halfway down the barrel has on accuracy. I have a direct impingement gun (old style) with a chrome bolt carrier assembly. after getting it all dirty I just take the BCA out and wipe it off. looks just like new.

 

[Big Al 29]

I was hell bent for buying a Piston over DI. I did a ton if research and everything swayed towards the piston until I started reading articles how the pistons don't like to shoot junk ammo. stove pipe city.

The articles stated if you shoot good brass mill-spec ammo you are groovy but if you shoot Wolf, Brown Bear, WPT, Tula, etc... you will be running into problems.

i know the pistons have a gas valve adjuster so maybe you have to tweak with it with every type of ammo you are shooting.

I just decided on the DI and run it wet. It will shoot anything then and keep the cost to shoot lower.

 

[Leo]

While I have never been in love with the AR system that blows crap right into the trigger group, especially since I run high grade triggers, but I found that a piston operated rifle is not exactly clean either. Any semi auto is dirty. Add high volume shooting and the filth is pretty significant. An AK is a piston operated rifle, and they get filthy. An UZI has no gas system at all, and they are full of soot after any extended period of shooting.

My employer bought a piston operated Stag Arms AR rifle for use as a rental. We already had regular design AR's. Part of my job was to clean rental guns. I was surprised that the piston operated version got nearly as dirty as the usual gas operated. I guess a lot of the filth is coming out of the cartridge case as it is extracted.

 

[W.R.Buchanan]

Frog Lube! greatest thing since sliced bread.

Keeps all of these .223 guns running perfectly. Nothing sticks to Frog Lube once it's cooked into the pours of the metal or plastic.

I jsut did a 4 day rifle class at Front Sight last week and my Kel-Tec SU16CA ran well all week without cleaning.

After getting back home and cleaning the gun the only dirt was in the gas tube which is where it should be.

The gun would have ran for another 400 rounds easily. That would be 800 total.

Randy

 

[JH]

Tsk....tsk....tsk....you really need to go to other websites for more information......H&K, LWRC and LMT gas pistons eat DI guns for lunch......

Your Sig is an average to below average weapon that is a good value...if you want DI move up the food chain and start with Colt and move up from there: BCM, DD, LMT....eventually you will get to LaRue, KAC and Noveske....

You really need to get information in other sites...this is a "trapshooters" website.....

 

[Brian in Oregon]

<i>"Knowledgeable folks in the industry will tell you that IF you run a can or SBR, the piston driven gun may be better."</i>

Knowledgeable folks in the industry will also tell you that a gas piston can give you a big pop out its exhaust port when using a suppressor, and that the original gas system is quieter because the bolt and bolt carrier act to reduce the gas energy and muffle it. That's the trade off for less junk going into the bolt from the suppressor back pressure.

While not an SBR, here's a 16" barrel with a carbine gas system. The muzzle report is similar to a .22 WMRF in a 24" barrel or a .22 Mini-Mag or Stinger in a 16" barrel. The same suppressor on a gas piston gun makes a noticeable pop out the exhaust port.

As far as what Bangalore is asserting, he's right. If you want a good, reliable gas piston gun, it's a good idea to ante up for one of the better makes. As I mentioned earlier, these are proprietary systems, so how long the parts last depends on quality, and replacement parts will depend on how long the maker is in business.

 

[Shooting Coach]

Brian's last paragraph is Gospel. Wait until the fuss dies down and buy a $700 AR, or buy a $2K piston gun. DUH!

As one who has bought and sold Title II arms, including cans, a suppressor is hard on a gun. A high performance autoloader like the AR series overheats QUICKLY with a can.

I also said under certain circumstances, the piston gun MAY be better. I would stay with the soda straw blowing crud into the action. These guns have been around a long time, and they work.

 

[JH]

Hmmm....pistons have been proven reliable since WWII.....many a machine gun is piston driven.....H&K does very well, thank you very much......

It depends if you are into suppressors noise issues or full-auto.....sustained full auto guys like pistons better.....

Shooting Coach: A $700 DI non-Franken gun that is worth a hoot? Really? Name it!