Can Someone Please Explain?

[Single Six]

Not expecting a boat load of replies here, just needing a solid answer to a question I sincerely don't know the answer to. First off, understand that I'm neutral when it comes to AR rifles; I am issued a Colt M4 by my LE agency, but if left to my own devices I prefer a Mini 14. Anyhow, to the point: I keep hearing this debate that piston-driven AR rifles are somehow superior to the standard design. Is this quantifiable in any way, or just another on-going argument for the forums and magazines? Thanks, guys.

 

[rantingredneck]

The rationale is that the DI (direct impingment) rifles "crap where they eat." Meaning that the gasses that cycle the action are driven directly into the action itself creating carbon fouling buildup on the bolt and in the chamber/action. With a piston action the gasses push the piston which pushes the bolt and allows for less direct fouling of the action.

Is it quantifiable? Yes in terms of how much cleaner a piston rifle runs.

Is it quantifiable? In terms of whether one system is better/more reliable? Dunno..........

 

[theinvisibleheart]

yes and no.

Gas impingement system like used in AR15/M16/M4 becomes an issue only if you shoot a lot(300-400 rounds) w/o cleaning and/or if you are in dusty environment like Middle East/Afghanistan.

If you really like Mini-14, go for it.

That said, gas piston system tend to be much cleaner.

 

[rattletrap1970]

I've just never used a mini 14 that was accurate as an AR. I'm not saying they can't be, I've just never seen it. Also, your customizability of an AR far exceeds what is available for a mini 14. You can make an AR a CQB rifle, and long range engagement rifle, you name it.

 

[Single Six]

Hmm..okay, I get what you're saying. So it looks like the chief advantage is that the piston driven rifles just run cleaner. Well, it seems to me that that is a good thing; the cleaner the rifle, the longer it should run with minimal chances of a malfunction. Makes sense to me. Thanks again, fellas.

 

[Jimro]

Single Six,

Just remember that not all gas piston systems/rifles are made equally reliable. Every system has a failure point, if it didn't it wouldn't be a system

Jimro

 

[theinvisibleheart]

Correct. I've shot original AR-180(gas piston successor to AR15/M16 which was never adopted by US military) and I liked it better than AR15/M16.

AR-180/18 formed the basis for many other guns adopted by government around the world such as Singapore, Germany, etc.

There's nothing wrong with Mini-14 design and it's a fine combat weapon.

 

[Single Six]

Rattletrap1970: I completely respect your opinion on this, and thanks for posting. For my purposes [home defense and patrol duty], I personally don't get too concerned over whether my rifle is an MOA shooter at 100 yards. Our M4s don't have scopes, irons only, and our feeling is that long shots calling for precision shooting call for a dedicated sniper rifle. For me and my co-workers, we mainly just care that our rifles are reasonably accurate at reasonable rifle distances and that they be reliable. In my own personal experience, I've seen AR rifles jam...I've never seen a Mini jam. I'm sure it's happened to someone somewhere, just hasn't happened to me [yet!]. Also, I do agree with you on this point: There are plenty of aftermarket accessories out there for the Mini, but nothing compared to the industry that exists to customize the AR. Still, I just like the Mini better...strictly personal preference.

 

[Tbag]

In the AR system the DI has been pretty much refined, where that piston is fairly new in an AR system.

I've have several DI AR's that have run 1000 to 2000 rounds in just a few days with no issues and minimal care. I'd stake my life on them if I had too.

 

[thekevster]

Hmm..okay, I get what you're saying. So it looks like the chief advantage is that the piston driven rifles just run cleaner. Well, it seems to me that that is a good thing; the cleaner the rifle, the longer it should run with minimal chances of a malfunction. Makes sense to me. Thanks again, fellas

Piston driven ar15s are cleaner that is true.
But no firearm stays clean forever no matter what you have to take care of your gear and your gear will take care of you.I wouldent put to much stress on this.
For your uses I think a direct impingement ar15 would work great if you take care of it (like any firearm).
AR15s are very dependable weapons despite what some people say.Watch this video below.

http://www.youtube.com/watch?v=u5CQOvdYW6c&feature=related

Another advantage of piston driven ar15s is they work better in water this is why Navy SEALs use them.

 

[Single Six]

Kevster: First, a belated welcome to TFL! Second: For me, a clean weapon is a foregone conclusion. Some newborn babies don't get the care and attention that my guns do when it comes to being clean....and that goes double for when I've just gotten through doing some shooting. We're on the same page here: I feel that I should give my guns every opportunity to work as they should, that means they stay clean.

 

[Bartholomew Roberts]

So it looks like the chief advantage is that the piston driven rifles just run cleaner. Well, it seems to me that that is a good thing; the cleaner the rifle, the longer it should run with minimal chances of a malfunction.

The problem with this assumption is that it assumes that the gas piston AR is in all other respects the same as the direct impingement AR (the standard design); but this isn't the case.

One of the problems with a gas piston AR is that the AR is designed to be direct impingement. The gas piston in a DI AR is part of the bolt carrier. When you try to put a more traditional long-stroke or short-stroke gas piston in the same space, you have problems. Here are a couple of common issues that occur:

1. Carrier tilt - A DI AR pushes the bolt carrier straight back because it uses gas to pressurize the space between bolt and bolt carrier - making the bolt carrier the gas piston as it were. On a gas piston AR, this happens around the front sight base and is used to drive an oprod rearward. The oprod strikes the carrier key on the top. Because there are no upper receiver rails in the AR and it is a round, tubular receiver, the bolt carrier tilts down in front and up in back when this happens. The tilt in back drags the bolt carrier across the buffer retaining pin and buffer tube. The opposite end of the carrier tilts up - dragging the top bolt lugs across the chamber lugs as they unlock. This same system also results in more violent unlocking of the bolt and greater stresses on the carrier key (which often has to be redesigned to withstand the increased stress).

2. Tiny op rods - the hole in the AR upper receiver is designed for a relatively small diameter gas tube that does not move. In order to put an op rod in the same space and still allow clearance for debris, movement, etc., you need either a really tiny oprod, a taller upper receiver or a combination of both.

Now these challenges aren't insurmountable. You can still make a good piston AR. However, it does mean that the knowledge base for piston ARs is smaller and they tend to have a lot of proprietary parts. And some pistons are better than others. However, there aren't any free rides. The price you pay for that cleaner bolt is a different set of problems.

 

[stellite]

I have tried to read up as much as possible on both systems. Neither is a solution for the other just an alternative. Both have advantages and disadvantages. Here is what I have found for both in reading from multiple sources.

Piston Pro's:
1. Does not blow gases into receiver as much as DI. Gasses still get into receiver from around cartridge so piston guns do get dirty from gas.
2. Can be used waterlogged so if you want to jump out of water like rambo it will work well.
3. Heat is not centered in receiver area it is centered around the midlength of the barrel. Not sure that this is an advantage.

Piston Cons:
1. Heavier
2. More moving parts to break(piston, piston spring)
3. Higher mass of moving parts causes higher felt recoil and more wear and tear on receiver.
4. Heat is centered at the barrel instead of pushed back to the receiver. Barrel area near piston port gets very hot. This can affect accuracy and barrel life. So this one is a wash. Heat is just in a different place.
5. Piston systems without rails cause a torque or moment on the bolt called bolt tilt which can cause premature wear. properly designed systems won't have this problem.
6. accuracy is not as good as DI.

in the end it is a different system not a better one. There is an article on "why piston systems suck" or something like that in a recent magazine. I know there has been articles like that on DI. I would not let the system choose the rifle for you.

 

[Single Six]

Bartholomew and Stellite: Very thought-provoking posts from both of you. Most appreciated. I should clarify that I have no intention of shopping for an AR of any stripe; I really just got my curiosity aroused by all the recent discussion in the magazines and thought I'd see what my TFL brethren had to offer.

 

[ipscchef]

I am not an LEO,an "operator", I don't do anything tactical that I am aware of, but I have a Bushmaster and a Mini 14. My Mini is almost 30 years old with many, many rounds through it, and as fine as my Bushy is, my bedside gun is still the Mini. I realize that the AR platform is used by the military, for I am sure many, many, reasons over the Mini, but for most of us, I have to agree with the OP, for my needs it is plenty of gun to do whatever needs to be done. I can hit a beer, uhhh, soda can with it at 100yds 6 out ten times if I do my part. For home defense, stoked with 30 55gr. HP's I feel comfortable that is a great choice for MY family in MY home. JMHO, and as always, YMMV. The OP stated that he is LEO, so I do not have any real world input, but I think IF I were in that position, I would still feel the same way about my Mini, with the right loads it would get the job done.

Willy

 

[Scorch]

Not taking a position one way or the other, but this one has been beat to death. The US military concluded their tests on piston-driven AR systems and concluded there was no benefit to the piston system over direct impingement. So, if the US military cannot find a benefit to piston-deiven AR systems after testing thousands or rounds and spending millions of US taxpayer dollars, what makes you think a bunch of internet "experts" can (many of whom, I might add, may have never owned any AR, let alone a DI and a piston AR)? FWIW, I own a DI AR, and it has never failed. I also carried M16A1 and A2 in the USMC, and those never failed either.

As far as AR vs Mini-14 or Mini-30, that one has also been discussed at length. IMO, ARs are more accurate, so ARs are more interesting and more fun, but Minis are super reliable and tough as nails.

 

[pythagorean]

Not expecting a boat load of replies here, just needing a solid answer to a question I sincerely don't know the answer to. First off, understand that I'm neutral when it comes to AR rifles; I am issued a Colt M4 by my LE agency, but if left to my own devices I prefer a Mini 14. Anyhow, to the point: I keep hearing this debate that piston-driven AR rifles are somehow superior to the standard design. Is this quantifiable in any way, or just another on-going argument for the forums and magazines? Thanks, guys.

You have asked three questions in this post.
I will try to answer all three:
1.M4 v Ruger Mini 14. The Mini 14 is a civilian weapon not on any battle field.
2. Piston driven: choose the AK 47 Kalishnikov if that is where you want to be.
3. The American response is the M4 above the Russian (USSR or Chinese or Yugoslavian or Romanian) entry.
4. Lastly,
The "piston v direct gas impingement (like the M4)" will continue depending upon your scientific reasoning capacity.

Buy the SIG 556 Tactical or other "M4" Platform with an extra piston attached to any rifle and compare with what the Army uses.
Or continue to choose elsewhere and argue you are the best in choosing the best design.
In the end the M-4 from Colt is the end.
I rest my case.
Do you need an M-4 chart to compare? I did this repeatedly and in the end most with sense acceded.

 

[pythagorean]

Pictures of my Colt LE 6920. It uses the Army M4 frame and says so on the front of the frame above the barrel.
The only difference is that the 6920 is semi auto fire--with all the rest according to US Army M4 standards.
There is no better weapon for LE in my understanding unless you want to go into 7.62--NATO; not Communist AK ssssi or hit or other spelling.
Then You choose the M-14 or Socom 16 and be done with all argument.

For civilian LE the Colt is enough. For War the SOCOM 16 is better.

 

[pythagorean]

Or buy the SIG 556 like me and figure it all out:

I sold the SIG 556 Tactical.
The chamber and bore were NOT chrome lined. I didn't have much problem cleaning the piston chamber--but I felt the Colt LE 6920 was better in all after shooting downrange with all bullet weights up to 79 grains.
And no rifle manufactured today beats Colt in the 6920 period. I've been watching.

 

[stellite]

you sound like a Colt infomercial