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sdclaw
July 26, 2012, 12:18 PM
What are some of the pros and cons of piston and gas?

Creeper
July 26, 2012, 12:49 PM
In a nutshell...
Piston ops run cooler and cleaner, require minimal lubricant and less cleaning, and may be more reliable in extreme environments.
Standard DGI rifles may require a slightly higher level of lubrication, run warmer in the upper receiver, may get quite a bit dirtier in the upper receiver, if over lubricated may fail in an extreme environment, and may be, gun for gun, a bit more accurate.
I know... lots of "may's" there. The argument will go both ways dependent on the objectivity or personal experience of the arguer.

General consensus (and there will be arguers here too) is, if you're a freak for accuracy, go gas. If you're a freak for potentially superior reliability under any and all conditions, go piston.

There are other positive and negative attributes, but those are the primary ones.

On a personal note, I tend not to drag my ARs thru desert sand, mud and rotting undergrowth... and I keep them clean, so I'm quite happy with DGI.

Cheers,
C

cannonfire
July 26, 2012, 01:00 PM
Piston has more moving parts, which leads to more potential for parts breaking. The heat is not transferred into the BCG but leads to heat build up of the piston itself. Still have to clean carbon build up on piston system. Carrier tilt was a problem but I think it has been generally fixed

DI runs dirtier and hotter in the upper reciever. Proper lube will negate the build up and allow to keep running as long as carbon does not solidify to BCG. DI may need more maintance when cleaned.

I'm partial to DI system for the simple fact that it is less moving parts and less complicated of a system

plouffedaddy
July 26, 2012, 03:07 PM
I've had both but only have DI now.

Piston pros:
1. Way cleaner. You can shoot 500 rounds and it'll be cleaner than shooting 50 DI.
2. Adjustable gas settings

Piston cons:
1. Cost
2. Less accurate. This is ultimately why I sold it. My groups were about 2'' bigger at 100m than with my DI guns.

If you're one of those people that hate cleaning your guns, get the piston. Otherwise, I'd just buy more ammo and some CLP with the leftover money you'll have buying the equivalent DI gun.

pturner67
July 26, 2012, 03:18 PM
good video on this by nutnfancy...skip forward to about the 5:30 min mark for a comparison, etc

http://www.youtube.com/watch?v=6auXTiqNtEo

Quentin2
July 26, 2012, 03:51 PM
As far as ARs, the biggest con for the piston is there are multiple piston systems with no standard so far. No doubt there will be a shakeout down the road so you could be left with an orphan system that its manufacturer has abandoned. You'd want to get parts right then before they dry up. This is similar to the situation with the various incompatible AR-10/.308 rifles out there now.

Of course this is not an issue with the 50+ year old DGI standard, except possibly for the fairly rare intermediate gas length (where you might have to cut off a rifle length gas tube). Otherwise with a DI AR you enjoy a system that is pretty much compatible with the multitude of other DI ARs out there.

Bartholomew Roberts
July 26, 2012, 04:26 PM
There is no easy way to compare pistons as a whole to DI because there are a dozen different piston systems out there and they all use different approaches. DI amongst the various manufacturers tends to be standardized.

As to the piston running cooler, the one time I've seen someone try to qualify the difference, the piston bolt face (SR556) was 30F cooler after 5 magazines compared to the DI rifle (LE6920). POF has shown some better numbers on heat; but they also use a giant heat sink/barrel nut on both their DI and gas piston rifles that is more likely the source of the difference.

jason41987
July 26, 2012, 04:56 PM
haha.. nutnfancy videos... chubby kid who played too much call of duty pretending he's actually giving advice to special forces... some good advice is if you want to learn more about a firearm, skip his videos as a 10 year old buy could do a better job

Eghad
July 26, 2012, 06:17 PM
If you want a piston gun get one but unless you are going to shoot hundreds of rounds at a time or fire FA a direct impingement system will work for you. You can also buy a Anderson DI gun treated with RF-85 that you clean with soapy dishwater and use no oil on.

INMY01TA
July 26, 2012, 06:46 PM
Piston systems are great, on guns that were designed to use them.

Acc371
July 26, 2012, 07:04 PM
I researched both heavily in preparation for my 1st build.

My conclusion (Similar to Creeper) is:
Unless your going to run through 500-1000+ rounds per month or "drag your AR thru desert sand, mud and rotting undergrowth" just go with a DI.

I skipped the AA kit & just went DI. I'm happy with my decision.
I did make one concession; I went with a closed end instead of a forked muzzle device, due to going through branches & vines while I'm hunting.

Eghad
July 26, 2012, 07:17 PM
On most well made AR-15s you can drag them through the water, mud, swamp and sand and they will still function. Just make sure the barrel is not plugged or it may not matter which system you have

Sinlessorrow
July 26, 2012, 08:38 PM
My conclusion (Similar to Creeper) is:
Unless your going to run through 500-1000+ rounds per month or "drag your AR thru desert sand, mud and rotting undergrowth" just go with a DI.

say what?

all I run are DI ar-15's, they easily see 1,000+ rounds a month and only get cleaned once every year, if that.

keep the AR-15 lubed and it will have no issue, read this from someone with 10,000 rounds through his M4 clone in the desert.

http://www.ar15.com/forums/t_3_118/564927_Why_I_like_my_LMT___.html

pistons do run cooler but the difference is at max 50*F on the bolt(the hottest part of the bolt carrier group) not enough to make a difference.

the main difference is DI runs dirtier but it has not effect on reliability.

Acc371
July 26, 2012, 08:53 PM
pistons do run cooler but the difference is at max 50*F on the bolt(the hottest part of the bolt carrier group) not enough to make a difference.

Got to do a "Say What? on this. 50o.
Take an AA Kit. The gas is expelled out the the back of the gas block. So, very minute if any gas gets into the BCG. So, I would think it would run a heck of allot cooler than just 50oF difference from a DI.

Sinlessorrow
July 26, 2012, 08:58 PM
wrong ACC, there have been tests done between piston rifles and DI Rifles and the bolt was only hotter by 50*F after 5 mags on auto, this was compared to the HK416(the best piston AR)

ETA here it is and its not even a 50*F diff.

Colt M4

Flash hider: 423
Barrel: 343
Gas block: 360
Upper: 150.5
Carrier: 130
Bolt: 90

HK416
Flash hider: 300
Barrel: 281
Gas block: 338
Upper: 103
Carrier: 102
Bolt: 78

Acc371
July 26, 2012, 09:11 PM
Whatever you say man.
Have a good one!:)

http://www.youtube.com/watch?v=H3TVsekcFWo

Sinlessorrow
July 26, 2012, 09:13 PM
wow a poor animation that does not really illustrate how the DI system runs? did i mention they are trying to sell a product?

you do know the DI system vents all excess gas thats not needed when it cycles right?

dont believe me? here is the link to the results.
http://www.m4carbine.net/showthread.php?t=57400

cannonfire
July 26, 2012, 09:25 PM
Wow, I guess I was off with my statement about the heat just being relocated

Disregard my statement earlier

Acc371
July 26, 2012, 09:26 PM
I know they are trying to sell something. I just wanted to show the part on how the 2 systems work.

Thanks! Very interesting link.
Later!
:)

sailskidrive
July 27, 2012, 06:21 AM
The biggest problem I see w/ the piston guns is that there are no standards. It's not like the piston is part of the design package that the manufacturers can either license or copy; instead everyone is doing their own thing.

POF, Colt, SIG, Hk, Adams Arms, LWRC... everyone is different. Most of them are well made, the issue is if you needs parts.... 20 years from now. ;)

I have a SIG716 (308) and the Bolt Carrier Group appears to be the exact same as LWRCs; I'm sure others are sharing designs but in general it's still the Wild West.

Rogervzv
July 27, 2012, 07:50 AM
I used DI rifles for years in the Army. That caused me to develop a cordial dislike of the DI system. It is dirty and inelegant the way it dumps all of the discharge gasses right into the bolt carrier group. Only a Government contract would result in a design like that.

By contrast, a piston rifle is a far more elegant solution that keeps the waste products away from the bolt carrier group, which is the most critical system in the rifle.

It is true that modern ammo is a lot cleaner than the ammo that caused the DI system in early M16s to have such a terrible maintenance record. But that does not change the fact that the DI system is what it is.

Hey, DI works, it is cheap, and since the Government adopted it there are a lot of parts and rifles that use it. Just know it for what it is. I prefer piston but that's just me.

madcratebuilder
July 27, 2012, 07:52 AM
Piston systems are great, on guns that were designed to use them.

Bingo!

Sinlessorrow
July 27, 2012, 08:04 AM
I used DI rifles for years in the Army. That caused me to develop a cordial dislike of the DI system. It is dirty and inelegant the way it dumps all of the discharge gasses right into the bolt carrier group. Only a Government contract would result in a design like that.

You shoukd get a few things straight.

First off it doesnt just dump all the gas into the BCG. it siphons off a small amount of gas(around10%) as the bullet passes the gas port it is led down the gas tube, into the carrier key where it is channeled into the bolt carrier right behind the bolt tail, at this point the gas starts to expand sending the bolt carrier back.

As the carrier is moving rearward the cam pin unlocks the bolt and the rifle begins to cycle, once the bolt is fully unlocked the excess gas is exhausted out of the exhaust holes in the carrier.

Also the .gov did not design this system, eugene stoner did in his garage, he then marketed it to the military in the AR-10, but being late to enter his rigle it was rejected and the M14 was chosen.

It was only after being sold to Colt that the AR-15 went anywhere.

It should also be stated the Military has no idea how to run the M16FOW any better than a FUD at the gun store. The military teaches white glove cleaning, less lube is better cause sand sticks to lube, and that you have to stagger gas rings........None of which is correct.

Rogervzv
July 27, 2012, 09:51 AM
Sinlessorrow said:

You shoukd get a few things straight.

Actually, I'll stand buy what I said. The DI system is inelegant and dumps crud right onto the bolt carrier group. Poor design concept. Good engineering and cleaner rounds and rigorous maintenance were required to make this a viable concept which does not change the fact that it is an inelegant design. Piston is better when done by good companies like Ruger who know how to design and manufacture rifles.

Nice that you don't think that the US Military knows how to maintain or operate M16s. If they can't do it after 50 years I am sure hobbyists like most of us here on this forum will do better. :D Actually, your claim that after 50 years the military is still struggling to get the DI system to work right illustrates the inherent poor design inherent in the DI system.

I find that the military-style white-glove weapons maintenance regime works quite well for all my weapons and that's what I do because that is what I was trained to do and what I trained others to do. And because it has worked for me.

Sinlessorrow
July 27, 2012, 10:32 AM
I find that the military-style white-glove weapons maintenance regime works quite well for all my weapons and that's what I do because that is what I was trained to do and what I trained others to do. And because it has worked for me.

That right there^^^

That is why the military is clueless about how to properly use the M16FOW.

Why do it the right way when the wrong way works, it just deadlines part quicker but it works.

Im sorry but the fact that you refuse to learn is no excuse, white glove. Leaning the M16FOW does more harm than good, it strips away protective coating and damages parts before they would be had they been properly cleaned.

You think a piston would be different? You ever try cleaning the piston on the M27IAR? Yep same senseless scraping that kills the piston before its time.

It doesnt matter what rifle we get or have if we continue to overclean rifles.

By cleaner rounds do you mean what Stoner called for? Then got changed to a 7.62 powder? That led to excessive carbon build up and cyclic rates in excess of 1000RPM?

And by Rigorous maint. Do you mean a simple wipe down with a rag and relube daily to keep it running in afghanistan?

Man the M16 is such a hog for cleaning I ONLY have to wipe it down and put some lube on it daily........yeah so rigorous.

You see the reason the Military has issues properly runnig the M16FOW is people like you who refuse to learn and change techniques and instead continue preaching what you were taught from someone from Vietnam.

There is no excuse and a piston makes no difference. The Stoner system is an incredibly simple system with fewer parts than most and its incredibly reliable when in the hands of a competant person.

How to keep the M16FOW running overseas.

1. Field strip
2. Wipe down with rag
3. Scrub for 30 seconds with chamber brush and dry
4. Run bore snake down bore.
5. Relube, heavily with a good lube. The more the better.

There you go, that sure is a maint. Intensive system.

Rogervzv
July 27, 2012, 12:44 PM
Well, Sinlessorrow, the fact that we are fighting about how to maintain the DI AR platform rifle 60 years after its introduction simply illustrates the problems of the DI system.

FWIW none of my personal rifles have ever suffered any kind of parts failures in 40 years of shooting so I am pretty happy with "the Army way." It has worked for me.

You are entitled to your opinion, of course.

Ralgha
July 27, 2012, 02:03 PM
wrong ACC, there have been tests done between piston rifles and DI Rifles and the bolt was only hotter by 50*F after 5 mags on auto, this was compared to the HK416(the best piston AR)

ETA here it is and its not even a 50*F diff.

Colt M4

Flash hider: 423
Barrel: 343
Gas block: 360
Upper: 150.5
Carrier: 130
Bolt: 90

HK416
Flash hider: 300
Barrel: 281
Gas block: 338
Upper: 103
Carrier: 102
Bolt: 78

This test looks fishy to me. Why is the HK416 so much cooler in the flash hider and barrel? Actually I probably know why, different materials, thicknesses, etc. My point is, if those are so different when they should be roughly equal in a fair test, we can't draw a conclusion of upper temperatures in piston vs. DI.

A better test, and one that I would like to see, would be one where two identical DI AR-15s are acquired and then tested after modifying one with an after-market piston system.

Sinlessorrow
July 27, 2012, 05:33 PM
how do i quote?

Ralga, one thing to note is the HK416 barrel is incredibly thick, almost double that of the standard SOCOM profile M4A1 barrel, that is part of why its cooler, but also why the 10.4" 416 is heavier than the SOPMOD II M4A1.

to roger, I agree we each have our opinion, but I dont think it shows anything about the DI system.

as I mentioned the Marines clean their M27 just like they do their M16A4's and M4's. the only diff is instead of scrubbing the bolt tail they are scrubbing the piston. what this does show is that no matter the rifle the Military expects you to scrape and scrub till its white glove clean.

there is the wrong way, the right way, and then there is the military way.

there is a reason people like Pat Rogers no longer scrape and scrub their rifles religiously.

Creeper
July 27, 2012, 06:01 PM
how do i quote?

The text you want to quote will go inside this: Substitute the '3' for an 'E'.
You can also click the http://thefiringline.com/forums/images/editor/quote.gif box above and to the right to wrap the same tags around your selected text.

Sometimes the quote button will look like something else (occasionally, it's a smilie on my 'puter)... just remember that its the second button from the right.

To install the name of the person you are quoting, a equals sign and the name will go into the first text wrap, like so: [QUOTE=Sinlessorrow]

Cheers,
C

Eghad
July 27, 2012, 06:47 PM
I had a Colt DI AR 15 H Bar Pre-ban that I bought in early 1994. It was still working and in good condition 15 years later when I traded it in because I wanted a Flat Top Upper. I might try a gas piston model when they give me a good reason too.

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

TNT
July 28, 2012, 08:21 AM
PROS piston
Reliability
Cleaner shooting
Cooler operating temps
easy break down (depending on design)

I have used the DI systems for years while in service 20+ to be exact but I was never really sold on them they are more finicky than the piston designs. the are dirtier run hotter break downs are the same and accuracy is the same. Now they are in use today still making the M16 AR platform the longest serving rifle in service to date. Does it make it the best IMO no. Only one way to go and that is Piston. Its cleaner running, more reliable, easy break down, and they are accurate.

Arizona Smithshooter
July 28, 2012, 08:49 AM
This will always be a No-Win argument. My only observations come from owning and shooting both types, plus seeing what new products are being offered by major gun manufacturers, and many of those are of the piston design.

My M&P 15 piston has been the best rifle I have ever owned. Reliable, accurate, and very easy to clean and maintain. That's all I ask in any rifle and my S&W fits that to a "T". All other arguments for or against are irrelevant.

sailskidrive
July 28, 2012, 08:57 AM
I have used the DI systems for years while in service 20+ to be exact but I was never really sold on them they are more finicky than the piston designs. the are dirtier run hotter break downs are the same and accuracy is the same. Now they are in use today still making the M16 AR platform the longest serving rifle in service to date. Does it make it the best IMO no. Only one way to go and that is Piston. Its cleaner running, more reliable, easy break down, and they are accurate.

Accuracy on the piston guns is usually not as good do to harmonics and flexing of the barrel to upper joint as a function of the moving parts. While it is barely measurable at 100 yards it becomes a more obvious factor at 500-600. AK 47s are notorious for this problem as they are significantly less rigid due to the the use of stamped steel for the receiver.

I think piston designs in general are a great idea, unfortunately retrofitting the AR platform has been problematic with various issues which we've all probably read on here ad nauseum. Personally I like the POF and LWRC designs; I have a SIG716 and SIG seems to have solved the carrier tilt issue with groove in the carrier to help align in.

TNT
July 28, 2012, 09:49 AM
I think piston designs in general are a great idea, unfortunately retrofitting the AR platform has been problematic with various issues which we've all probably read on here ad nauseum. there may be some truth to that on the AR's but the Garands never had that problem there were capable of accurately hitting at 500 yds. (they are capable at 1000 yards) But it may be due to retrofitting the AR to work with it. I have never personally seen what the accuracy was with the piston AR's So maybe its a design flaw And maybe the Garands are the exception to the rule IDK just saying. :cool:

SR420
July 28, 2012, 09:57 AM
I started using the DI system in the late 70's and owned several. Even though I never had a serious problem with any of them, I don't own a DI rifle today.
All of my semi auto long guns are piston driven. I prefer the cleaner, cooler running piston system and it really shines when using a sound suppressor.

Crow Hunter
July 28, 2012, 10:20 AM
http://www.m4carbine.net/showthread.php?t=107613

Here are Larry Vickers thoughts on the matter.

He was involved in the creation of the HK416.

As to the viability of piston guns.

Keep in mind which ones have actually been used in combat and how long they have been in production and what companies produce them if potential self defense/"combat" are your intended use.

As long as you are comfortable and confident in whatever choice you make and you can make the shots that you need to on the targets you need/want to shoot, it doesn't really make a lot of difference in the long run.

Sinlessorrow
July 28, 2012, 11:02 AM
Here are Larry Vickers thoughts on the matter.

He was involved in the creation of the HK416.

As to the viability of piston guns.

Keep in mind which ones have actually been used in combat and how long they have been in production and what companies produce them if potential self defense/"combat" are your intended use.

As long as you are comfortable and confident in whatever choice you make and you can make the shots that you need to on the targets you need/want to shoot, it doesn't really make a lot of difference in the long run.

excellent point.

the HK416 design actually started because they needed a 10.4" rifle that had longer parts life.

I will say in the 10" package a piston is the better choice. in the DI system you get around 5-7k bolt life in the MK18. the 10" HK416 has a bolt life of 12k thats a huge difference.

Arizona Smithshooter
July 28, 2012, 11:20 AM
Here is more info on the M27 (HK-416) Infantry Automatic Rifle now being used by US Marines...and it is a piston rifle.

http://www.tac-tv.com/videos/tac-tv-season-2-ep.-2-the-m27-iar

http://www.youtube.com/watch?v=xbmYYs3bdbo

https://en.wikipedia.org/wiki/M27_Infantry_Automatic_Rifle

and more fuel on the fire:

M16/M4 reliability problem, increased bolt friction causing jams

http://www.youtube.com/watch?v=6JmIQXkoog8

Sinlessorrow
July 28, 2012, 11:57 AM
Here is more info on the M27 (HK-416) Infantry Automatic Rifle now being used by US Marines...and it is a piston rifle.

http://www.tac-tv.com/videos/tac-tv-...-2-the-m27-iar

http://www.youtube.com/watch?v=xbmYYs3bdbo

https://en.wikipedia.org/wiki/M27_In...utomatic_Rifle

and more fuel on the fire:

M16/M4 reliability problem, increased bolt friction causing jams

http://www.youtube.com/watch?v=6JmIQXkoog8

lets see the M27 IAR is an infantry automatic rifle.

its designed for high volumes of automatic fire which is one area a piston excels in, the main issue for the M4 and M16 is the gas tube in high volume firing sessions, something the M27 doesnt have to worry about.

alos the M27 has not replaced the M16FOW in the Marine Corps, it replaced the M249. the Marines are mostly only foot so the M249 was an interim solution till they could get a good IAR, they had the BAR, now they have the IAR.

the IAR(or BAR back in the day) is a doctrinal thing that the Marines have always had, kind of like every Marine is a rifleman(the reason they are reluctant to replace the M16 for the M4) and like how MARSOC is now using the M45 handgun when there are far better and more durable handguns in todays market. its all a doctrinal thing.

also your last video is a pile of crap, whatever that guy is talking about in that video does not exist in a real M16, I have never once seen any issues with the cam pin binding and I have never in my life heard of it.

DMZX
July 28, 2012, 05:13 PM
also your last video is a pile of crap, whatever that guy is talking about in that video does not exist in a real M16, I have never once seen any issues with the cam pin binding and I have never in my life heard of it.

Something looked rather fishy about that. So....

I tried to replicate what that guy did with the bolt to see if it would bind in the receiver, as shown in the video. Nope!

What that guy is doing is lifting the receiver with his off camera hand to make it appear that the bolt is stuck. I am not sure what his point is even though he says that the binding can be fixed with "some slight modifications to the bolt."
:rolleyes:

Smit
July 28, 2012, 08:37 PM
Ultimately, I think it's still too soon to make any solid judgement which is better than the other. Just look at the 1911, over 100 years old and companies are still finding ways to improve their overall reliability, accuracy, etc...

Most of the comparison studies/videos I have seen seem to be very subjective to whatever the presenter is trying to sell or prove their point as correct. Also, most of the studies arent even close to having enough sample sizes. Statistical comparisons require large sample sizes to "weed" through the crap in order to find what your looking for.

My thought on it was always less moving parts= less problems. But again, this could be absolutely wrong. Too soon gents, too soon.

Creeper
July 28, 2012, 08:40 PM
Just look at the 1911, over 100 years old and companies are still finding ways to improve their overall reliability, accuracy, etc...

And yet... the originals still do a pretty decent job of going bang. ;)

Cheers,
C

Sinlessorrow
July 28, 2012, 09:38 PM
Ultimately, I think it's still too soon to make any solid judgement which is better than the other. Just look at the 1911, over 100 years old and companies are still finding ways to improve their overall reliability, accuracy, etc...

Most of the comparison studies/videos I have seen seem to be very subjective to whatever the presenter is trying to sell or prove their point as correct. Also, most of the studies arent even close to having enough sample sizes. Statistical comparisons require large sample sizes to "weed" through the crap in order to find what your looking for.

My thought on it was always less moving parts= less problems. But again, this could be absolutely wrong. Too soon gents, too soon.

yep, MARSOC just began purchasing the M45 a new 1911 based off the Colt Rail Gun.

Once the PiP gets finished we will have a new M4 system that will take the cake and eat it to compared to other piston guns, the current piston ones are even to the SOPMOD Block II M4A1's and once the M4 gets a new BCG and new barrels and a FF rail system. well only time will tell.

Quentin2
July 29, 2012, 12:22 AM
As far as ARs, the biggest con for the piston is there are multiple piston systems with no standard so far. No doubt there will be a shakeout down the road so you could be left with an orphan system that its manufacturer has abandoned. You'd want to get parts right then before they dry up. This is similar to the situation with the various incompatible AR-10/.308 rifles out there now.

Of course this is not an issue with the 50+ year old DGI standard... with a DI AR you enjoy a system that is pretty much compatible with the multitude of other DI ARs out there.

I'm quoting myself (early in the thread) because it seems no one favoring piston ARs has addressed the issue. :confused:

Crow Hunter
July 29, 2012, 09:04 AM
One big advantage of the AR series is the lower receiver is the "gun", the upper is a part.

As long as you have a standard lower, grab whatever piston system you like for the upper. If it breaks or you can no longer get parts for it, just swap out the upper with whatever is available.

Pistons have some distinct advantages and if they fit your usage, go for it. (Heat in the receiver is NOT one of them. Think about it, if the combustion gasses were hot enough to effect the parts in the receiver, what would they do to the barrel and piston of the piston uppers? The gas is MUCH hotter where it is tapped off the barrel;))

If you are shooting a lot of full auto (with no opportunity to squirt a little lube into the action), need to swap from very short barrels to really long barrels on the same gun, have less than 14.5" barrels, do Over the Beach operations and need to shoot immediately after coming out of the water, do a lot of switching between suppressed/non suppressed, or need to shoot rounds with a large variety of pressure curves, get a quality piston system and enough spare parts to keep it running if you break something. (Chances are if you are doing this, the government buys your stuff for you anyway;))

Just be prepared to pay upwards of 2x or more the cost of a standard DI rifle and get the knowledge and parts that you need to become your own armorer should you need to become one because your company goes under or is banned from importation.

It is a free country, (right now) and you are free to spend your hard earned $ however you like.

Rogervzv
July 29, 2012, 10:33 AM
As far as ARs, the biggest con for the piston is there are multiple piston systems with no standard so far. No doubt there will be a shakeout down the road so you could be left with an orphan system that its manufacturer has abandoned. You'd want to get parts right then before they dry up. This is similar to the situation with the various incompatible AR-10/.308 rifles out there now.

Of course this is not an issue with the 50+ year old DGI standard... with a DI AR you enjoy a system that is pretty much compatible with the multitude of other DI ARs out there.
I'm quoting myself (early in the thread) because it seems no one favoring piston ARs has addressed the issue.

I suppose that this is one of the advantages of a DI gun. The parts are standardized across manufacturers. If you buy a piston AR rifle in my opinion you should buy from a manufacturer who has a reputation for standing behind their products. Ruger and S&W for example, to name just two. Companies like these will always be there to support their piston rifle products and I would not (and did not) hesitate to buy a piston-design rifle from either Ruger or S&W. Both companies' customer and product support are legendary. You do not have to "be your own armorer" if you buy from companies like these.

Quentin2
July 29, 2012, 02:55 PM
Still, the various AR piston system incompatibilities is a major CON! And a huge PRO for DI. :p

Guess you could say don't buy in to the con and hype spouted by gun magazines and people trying to sell you something - only buy a piston AR if you know for certain it has advantages for your application. For the majority of applications DI has and still works fine.

Arizona Smithshooter
July 29, 2012, 05:11 PM
Bottom line is we are all Americans with the freedom to chose whatever we want, be it anything from cars to guns. If we happen to be in a battle together and your DI gun quits, I will have your back. If my piston gun breaks I will expect the same from you. Who really cares...the guy at the muzzle end won't know the difference between a DI or PS...the end results will still be the same.

10-96
July 29, 2012, 07:40 PM
Does anyone know if any/how many pistons have made it to the top of the charts at Camp perry?

Heck , for that matter, does anyone know where to start looking?

Rogervzv
July 29, 2012, 07:40 PM
Still, the various AR piston system incompatibilities is a major CON! And a huge PRO for DI.

Just means a lot of manufacturers are copying a Government design.

Sinlessorrow
July 29, 2012, 09:19 PM
Does anyone know if any/how many pistons have made it to the top of the charts at Camp perry?

Heck , for that matter, does anyone know where to start looking?


I know.........none.........

Arizona Smithshooter
July 29, 2012, 09:52 PM
Beg to differ.......

M1 Garand, and M-14 have done very well.

http://www.m1-garand-rifle.com/gas-pressure.php

https://en.wikipedia.org/wiki/Gas-operated_reloading

kraigwy
July 29, 2012, 10:09 PM
Does anyone know if any/how many pistons have made it to the top of the charts at Camp perry?

NONE

But most of the Service Rifle events are CMP not the NRA, (Such as the EIC and Presidents 100, which require the service rifle. No piston guns are authorized.

Even in NRA matches where they can be used as Match Rifle, I've never heard of then placing (or even being used).

M1 Garand, and M-14 have done very well.

Yes, in their time, but they can't compete with the AR's now days.

Sinlessorrow
July 29, 2012, 10:57 PM
also not quite AR-15 but....

the DI M110 took the december USASOC sniper competition by storm.....

in the order they placed:
USASOC: 2x M110 w ACS stock kit

Dutch SF:1x AI, 1x Hk417 16"

10th Gp 2x M110 with Crane SOPMOD

San Diego PD: 1x 18" OBR.
1x Blaser .308

5th SFG
1x M110 wPRS
1x 16" OBR

10 SFG
2x 18" OBR

10 SFG
20" OBR w PRS
16" OBR

1 SFG
20" OBR
Mk13

10 SFG
2x 18" OBR

1 SFG
16" OBR
M110 w Crane SOPMOD

Unk SFG
Mk11 Mod0 w PRS
18" OBR


USMC SOI West :M110 w PRS, M110K1 w 762QDC/CQB

3SFG: 2x 18" OBR w SF can

7SFG: 2x M110 w PRS

1 SFG: 2x 18" OBR.

LSP Team (Louisiana State Police) .308 Bolt, 16" JP .308.

5 SFG : 2x M110 w Bushnell 3-20 Larue mount

10 SFG: 16" Larue New Gun 18" OBR. Both w SF Brake

Raleigh NC PD Team
2x 18" OBR w PRS

NC State Police Team
2x 18" OBR w PRS

Navy Team 1 (SEAL Team10 ?)
2x Mk20 SCAR SSR

Navy Team 2 (SEAL Team2)
2x Mk20 SCAR SSR

3 SFG
2x M110 w SOPMOD

Irish Defense Force
2x 20" Hk417

1st SFG
M24 in Chassis that uses AI mags (sorry Lazlo I forgot your compnaies name again) and Mk11 w PRS.

USMC SOI East: Larue Predator 16”, M40A5

3rd SFG
2x Mk11 Mod0 w SOPMOD

US Army Sniper School: 2x M110K1 w QDC/CQB.

DOE: 18" OBR, 16" OBR

ATF
2x Mk11 Mod0

3/75 Ranger
2x M110 with Crane Stock

1/75 Ranger
1x M110 with PRS
1x 16" OBR

Quentin2
July 30, 2012, 09:54 AM
Thanks for that information, Kraig!

Eghad
July 30, 2012, 06:11 PM
How many GP AR-15 varmint /accuracy rifles are built with a piston? Mine is DI.

For the vast portion of AR-15 shooters who punch paper on a semi regular basis whether you choose DI or GP it probably won't make a difference. I just run a Bore Snake with some CLP down the bore. Use some EWL Carbon Killer to hit the bolt and receiver areas hit the chamber with a quick brushing. Use Some EWL on the upper reciever and bolt and Im good to go in about 5-7 minutes after I shoot on my DI guns

10mm4ever
July 31, 2012, 06:41 AM
Stoner more or less admitted that he preferred the piston but chose DI due to the weight limits specified by the govt. His next design, the AR180, has a piston because Stoner designed it without any outside influence. The DI system is more accurate in rapid fire ONLY,due to the fact that the BCG has less mass.

Crow Hunter
July 31, 2012, 06:54 AM
Stoner more or less admitted that he preferred the piston but chose DI due to the weight limits specified by the govt. His next design, the AR180, has a piston because Stoner designed it without any outside influence.

Actually it was the AR-18 and he used a piston because Armalite/Fairchild sold the rights to the DI design to Colt.

Up until the patent expired, only Colt or those they licensed could produce the DI design.

After the patents expired, Stoner actually worked for Knights up until he passed away and worked on improving the DI design. (Bolts, cam pins, material improvments)

The AR-16 appeared in the later 1950s. The AR-16, a 7.62mm NATO selective-fire rifle, was Eugene Stoner's final design for ArmaLite. The AR-16 and its predecessor, the AR-12 were designed by Stoner in response to demands by the military forces of smaller, less developed nations for a less expensive, yet state-of-the-art selective-fire military rifle that unlike the AR-10 and AR-15, could be produced inexpensively of heavy-gauge sheet metal using automatic screw machines, lathes, and presses.[4][5] The AR-12 originally featured a direct-impingement (DI) gas operation system, but this was changed to a more conventional short-stroke gas piston in the AR-16 after ArmaLite sold the production rights to the DI system to Colt Firearms.[4] The AR-16 had a short, 15-inch barrel, hinged wooden butt, and weighed 8.75 pounds empty; only three examples were built.[5] Eugene Stoner left ArmaLite in 1961, shortly before Fairchild divested itself of ownership.[6]

The AR-18 was a scaled down version of the AR-16.

The U.S. military's later adoption of the AR-15 gave legitimacy to its 5.56mm cartridge, and ArmaLite sought to develop a competing design chambered in 5.56mm that did not infringe on the Colt licence agreement. With Stoner gone, it was decided to scale down the AR-16, and ArmaLite's new chief designer, Arthur Miller, embarked on the project. The resulting 5.56mm design appeared in 1963 and was named the AR-18. Miller later received U.S. Patent 3,246,567 for the rifle in 1969.

http://en.wikipedia.org/wiki/Armalite_AR-18

Sinlessorrow
July 31, 2012, 10:34 AM
Stoner more or less admitted that he preferred the piston but chose DI due to the weight limits specified by the govt. His next design, the AR180, has a piston because Stoner designed it without any outside influence. The DI system is more accurate in rapid fire ONLY,due to the fact that the BCG has less mass.

incorrect.

Crow Hunter has it right, this is easily seen by Stoners final rifle he designed the SR-25.

Stoner always intended his AR-10 to be DI. If the piston was his preferred method the SR-25 would have used a piston, but Stoner felt DI was and is the way to go and thus gave us probably the best AR-10 and subsequently the best AR-15 in the SR-25 and SR-16

Slamfire
July 31, 2012, 10:52 AM
I used DI rifles for years in the Army. That caused me to develop a cordial dislike of the DI system. It is dirty and inelegant the way it dumps all of the discharge gasses right into the bolt carrier group. Only a Government contract would result in a design like that.

DI is a dirty system which is why it is on the ash heap of history as regards military service rifles.

The real reason that Armalite used DI and configured the AR bolt is patent infringement. According Guns Magazine March 1957 “Is this the next GI rifle? http://www.gunsmagazine.com/1957issues/G0357.pdf Armalite had to work around existing patents.

As well all know, the adoption of the AR15 as a service rifle was a political matter, it was not based on technical excellence.

If you are to build a target rifle DI is a better system. Shooting Sports USA had an article where David Sams tested target DI versus Piston. Piston was not “awful” but DI was more accurate. What you would expect with less moving parts.

Sinlessorrow
July 31, 2012, 11:38 AM
DI is a dirty system which is why it is on the ash heap of history as regards military service rifles.

The real reason that Armalite used DI and configured the AR bolt is patent infringement. According Guns Magazine March 1957 “Is this the next GI rifle? http://www.gunsmagazine.com/1957issues/G0357.pdf Armalite had to work around existing patents.

As well all know, the adoption of the AR15 as a service rifle was a political matter, it was not based on technical excellence.

If you are to build a target rifle DI is a better system. Shooting Sports USA had an article where David Sams tested target DI versus Piston. Piston was not “awful” but DI was more accurate. What you would expect with less moving parts.

say what?

We must have a different version if history. The M16 had teething issues because of the way it was rushed into service and the incorrect powder being used.

Once Colt sent people over to check the problem they fixed them in the M16A1 that saw service near the end of Vietnam and ever since the M16FOW has been among the best general issue rifle in history.

The real issue is that people always want to bring up Vietnam when talking about the M16 but never admit that the M16A1 acually had very veryfew if any bad reports near the end of Vietnam.

To this day there are very veryfew bad reports with the M4, and the few that there are can be attributed to 1. Age of rifles, 2. Bad magazines, 3. Using the M4 as a LMG, 4. Lack of maintenance(read that as weeks without cleaning).

If anyone thinks a piston like the HK416 negates the need for cleaning your wrong. The HK416 requires as much lube as the M16FOW does, it still needs to be cleaned, and it will still fail you if you fail it.

There are reports of this online if you know where to look.

The M16FOW has served our country well once the M16A1 was fixed(BTW, every fix Colt did was specd by Stoner from the beginning), and the M16FOW will continue to serve for the forseable future, especially with the PiP in the works.

Eta: let me add, gun rags back in the 50's were just like gun rags today, take everything they say with a huge grain of salt. Stoner designed his sustem with a Piston, this is from Eugene Stoners patent# 2,951,424

It is a principal object of this invention to utilize the basic parts of an automatic rifle mechanism such as the bolt and bolt carrier to perform a double function. This double function consists of the bolt's primary function to lock the breach against the pressure of firing, and secondarily, to act as a stationary piston to actuate the automatic rifle mechanism. The primary function of the bolt carrier is to lock and unlock the bolt by rotating it and to carry it back and forth in the receiver. The secondary function of the bolt carrier is to act as a movable cylinder to actuate the automatic rifle mechanism. By having the bolt carrier act as a movable cylinder and the bolt act as a stationary piston, the need for a conventional gas cylinder, piston and actuating rod assembly is eliminated.
It is an object of this invention to provide a gas system which is lighter and less expensive to produce because of its simplicity than the present gas systems now used in automatic rifle mechanisms.

Crow Hunter
July 31, 2012, 11:40 AM
Interestingly enough.

The locking method of the AR is being carried over into all of the "next gen" rifles that I have seen the guts of.

The G36, SCAR 16/17, FN2000, Tavor TAR 21, and the ACR all use the same multilugged, cam pin rotated locking method of the M16 pattern rifles. The only difference seems to be the method of unlocking.

No one seems to use the AK method (2 lug long stroke) (except the Sig 550 series), M1 Garand/M14 (Short stroke, 2 lug receiver locking), G3 (roller locking), FAL (Camming block, reciever locking).

Anyone other than me wonder why that is?

What does the new Beretta 160 use?

Sinlessorrow
July 31, 2012, 12:00 PM
Interestingly enough.

The locking method of the AR is being carried over into all of the "next gen" rifles that I have seen the guts of.

The G36, SCAR 16/17, FN2000, Tavor TAR 21, and the ACR all use the same multilugged, cam pin rotated locking method of the M16 pattern rifles. The only difference seems to be the method of unlocking.

No one seems to use the AK method (2 lug long stroke) (except the Sig 550 series), M1 Garand/M14 (Short stroke, 2 lug receiver locking), G3 (roller locking), FAL (Camming block, reciever locking).

Anyone other than me wonder why that is?

What does the new Beretta 160 use?


the ARX-160 uses the standard 8 lug bolt.

The AK style bolt does not offer precise lockup every time which is one reason its accuracy suffers, the other issue is that if the extractor craps out it is not fixable in the field.

The bolt the M16 uses offers precise lockup every time and parts are easily replaced in the field if something breaks, it also offers 10,000 rounds part life under extreem firing schedules, and you can usually get 15,000 or so from normal firig schedules.

So you get a bolt that is accurate, easygo repair, and offers exceptional parts life.

The AK bolt gives you good parts life but thats it

PP99
April 5, 2014, 08:01 AM
"Piston systems are great, on guns that were designed to use them."
We agree. The PWS MK114 has become my favorite to go, let see what happens next… $.

boltomatic
April 9, 2014, 08:48 PM
Both are reliable systems, but the gas system requires more maintenance to retain that reliability. The accuracy advantage of the gas system only matters if you shoot in competitions, for hunting/range/self defense I would go with a piston for the reliability.

barnbwt
April 9, 2014, 11:27 PM
The Stoner bolt design allows for cheaply made barrel extensions in lieu of expensive, large, and heavy forgings. That's pretty much it for explaining its dominance, but it's a pretty big 'it.' It does the exact same thing as an AK bolt, rotate to lock the bolt relative to the barrel. There's no mechanism for 'consistency' being different between the two if both are made to the same quality (well, lug binding is more easily possible with the AR, but is a non-issue on a good quality make)

TCB

The Long Shot
April 10, 2014, 12:02 AM
It's a common misconception that piston rifles are less accurate than DI guns, that just isn't true. It is only improperly designed piston rifles that are less accurate. Gas pistons exert more force on an upper than a DI gun, so the upper receiver needs to be thickened. Piston systems also need to be designed so that the timing is correct, which many manufacturers don't do. Also, if you have a free-floated piston system (by that I mean that the piston and op-rod are in no way connected to the gas block or upper receiver) you will affect barrel harmonics less. All in all if you have a well-designed gas piston rifle you will have a very accurate rifle and a very reliable one. I have several POF rifles which shoot around .5 MOA, some shoot sub MOA with PMC 55 grain ammo.

I have also built a rifle which uses a custom upper and gas piston similar to POF's for personal use chambered in .308 with a Krieger barrel which is one of the most accurate rifles I own. I can put five rounds through what appears to be close to a single bullet hole.

I know from experience that piston AR's are MUCH more reliable than DI ones if you plan to abuse them. When an ex Special Forces officer tested a P415, he put around 30,000 rounds through it without cleaning it with flawless performance.

The only real downside of piston AR's is the cost if you want a well-designed one for accuracy. If you are looking for standard accuracy and extra reliability, there are many guns that fit that requirement. DI guns are very reliable if you clean them often, but if you want a gun to abuse, abuse, and abuse even more, a good piston AR can even surpass the legendary reliability of an AK! I am very partial to piston AR's because their functionality in mud, sand, and water has saved my life quite a few times. You can get a sub MOA DI AR for less than a sub MOA piston AR, but when you get to sub .5 MOA they cost about the same.

Also, piston AR's tend to preform better when switched to Fully Fun;)

Art Eatman
April 10, 2014, 09:58 AM
Odds are that the OP was satisfied, two years ago.