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Old November 12, 2012, 08:12 PM   #1
JW74
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Piston AR-15 Advice

Hello, I'm hoping for some input on a new AR buy. I'm in the market for a new AR in the 16" barrel length. I have narrowed it down to the Ruger SR556 and Sig 516. Both are piston operated and close in price. I wanted to hear from people that have shot both and which one would you recommend? What's good and what's bad about each?

I currently have a Bushmaster Predator with 20" barrel and scope that I like a lot. It's a great varmint gun but I wanted to add a shorter barreled AR with a collapsible stock that I would possibly put a Eotech on at some point or just keep the iron sights. Thanks for the advice!

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Old November 13, 2012, 12:19 AM   #2
chris in va
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Any reason why you want a piston rifle? How about just slapping an upper on your existing receiver?
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Old November 13, 2012, 12:40 AM   #3
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I'm also curious why you decided on a piston AR and chose those two models. You can get a lot more for your money, or even more for less money.
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Old November 13, 2012, 01:02 AM   #4
JW74
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I am for the most part fairly green when it comes to all the ins and outs of the AR platform but was thinking about going with the piston system as I heard it is cleaner than the gas system and easier to maintain/clean. Is this incorrect? As for those two models, they were both available at my local shops and I have heard positives about both and both had a good feel to me and had the type of rail system that I wanted. I am also looking for a gun with folding sights ect. I'm open to suggestions and advice. Thanks!
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Old November 13, 2012, 01:13 AM   #5
chris in va
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The whole idea with the AR platform is modularity. Just find the upper of your liking and fit it to the lower. Keep in mind piston uppers are generally heavier than the DI counterparts, and reliability is pretty much a wash. They do run cleaner though. It'll save you a few hundred bucks over buying a separate rifle.
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Old November 13, 2012, 01:40 AM   #6
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More reliable? Not really. Not in any realistically possible conditions anyway. (You don't plan on taking them to the moon do you?)
Easier to clean? Maybe, then again a direct impingement AR is not really that hard to clean anyway.

Like others mentioned. For the money you would dump on a piston AR. You can get a very nice DI rifle that will be just as reliable as the pistons and probably an overall better rifle. Plus have parts commonality with pretty much every other AR out there.
What happens when Ruger or Sig decide they don't feel like producing their rifles anymore, and yours breaks. Can't just swap in a replacement from another manufacturer. Since the all have their own proprietary system.
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Old November 13, 2012, 08:34 AM   #7
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Since you are already using a DI rifle, do you have problems keeping it clean/maintaining it?

Personally, I would go with what shared the most parts with something that I already had.

That being said, even if you do get a piston upper, and you later find out you don't want it or the supplier doesn't support it anymore, you can just swap to a new DI upper (or whatever the flavor of the month is at that time).

One of the great advantages of the AR family of weapons. The lower is the "gun".

I have heard really good things about the Sig 516 though. Supposedly one of the lead engineers from the HK416 program (the premier piston upper) designed the Sig 516 and added in some interesting improvments.
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Old November 13, 2012, 09:12 AM   #8
MikeGunz
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My buddy has the ruger, it is very front heavy. He was jealous of my DI gun with magpul hand guards on how light it was. Cleaning DI guns really isnt bad at all, dont let that be the reason you want a piston gun,
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Old November 13, 2012, 04:30 PM   #9
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I have a Barrett REC7. The total weight of the entire piston system is 3.3 oz. It is much, much cleaner operating than the DI gun I have.

You can argue theoretical reliabiity advantages as long as you want - there are pros and cons for both systems. I bought the piston gun because I wanted to see for myself if there was an advantage and not just read the opinions on Internet gun forums. Other than the super clean operation of the rifle - that's about it so far after having it for a year.

I've cleaned the gun once in 3K rounds and only because I wanted to disassemble it at that point to get an idea of what was going on with it. The piston in the REC7 is self cleaning - so even that doesn't get fouled and need cleaning. I dipped it in Carbon Killer and wiped it off - and a little fouling came off of it - but really not much. The white rag was just slighty grey.

The bolt / bolt carrier are unique to Barrett, but so is the bolt / carrier on a KAC AR. I understand the Erector Set interchangeable parts commonality fascination with AR owners - it doesn't matter to me - so I don't find that a liability with the REC7.

As to all of the "what if" parts failure scenarios - if I was that worried about it, I'd buy a second bolt, carrier, and piston system.
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Old November 14, 2012, 02:53 PM   #10
RadioFlyer8
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I decided to go with a DI build when I did do my build. I was looking into piston but decided not to mainly because of the little extra cost.

DI has worked for years as well.
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Old November 14, 2012, 03:53 PM   #11
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JW,

I own the Ruger SR556E (w/o chromed barrel and bolt) and it has been flawless after 5,000 rounds. I have never shot the Sig, so I can not give you a comparison there.

What I can tell you is that the Ruger piston system works very, very well. The gas block is adjustable for the type of ammo, which helps keep that spent brass going where it should. It also allows for the use of very light loads and extra power loads. Just turn the gas regulator with a bullet tip and continue fireing without worry! I have yet to have a FTE or FTF caused by the rifle. (I have had a few FTF from ammo).

Many people have cussed the piston guns for bolt carrier tilt and recoil buffer tube ware, but I have found that Ruger has solved the problem. My 556E tube is as pristine as the day I brought it home.

The bolt, carrier, and upper action remain cool to the touch after dumping 3 mags. But beware, don't touch the gas block, it gets scortching hot!

The 556E model does not come with the chromed bolt and barrel, nor does it have the four rail hand guard. The SR556 comes with sites and the 556E does not.

I found that the single rail of the 556E was much easier to hold than the 4 rail 556 model. The 556E does have pre-tapped mounting holes that you can attach rails to in any configuration you desire. The rails can be purchased in three lengths from Ruger. I chose to buy a 3" rail and mount in to the forward bottom of my handguard to mount a bipod on. I also purchased some Troy battle sights to go along with the Lucid red dot I mounted.

I think the rifle was around $1100.00 without the add ons and the sites/rail/reddot/bipod added another $300.00. Not bad for just what I wanted! And the gun will shoot <2 MOA all day, even when the barrel is too hot to touch!

BTW, I also own a few DI guns - DPMS and S&W- and they are fine weapons also.

I hope this helps you out.
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Old November 14, 2012, 04:31 PM   #12
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If you want a piston AR go with Ruger. I think it’s the best value for such a gun on the market and they are pretty close to 100% trouble free.

However I would point out a fact to you and the readership.

In semi-auto guns the piston is a perfect answer to a non-existent problem.
The thing that has caused failures in the M-16 family of rifles and carbine in the US Military’s action is heat. The idea is not valid that the “cleaner piston guns” make them work in sand better. They don’t

The heat from the Stoner system dumps on top of the bolt from the gas key in the carrier. The bolt heats up in full auto fire and in some actions, the amount of FA fire is enough to get the bolt over 900 degrees. I have heard from some folk in Va that it can go even hotter in some cases.
If you take steel and heat it quickly and cool it slowly, and if you do it enough times, you can soften the steel. It’s called annealing.

So, the bolt body gets hot. It cools slowly. It’s hot right where it’s the thinnest, at the cam pin hole. If that gets a bit soft it can elongate in use. Only a few thousandths is enough to make the pin “slap” back and forth as it locks and unlocks. As that continues you see cracks develop at the pin hole. After time the crack can turn into a break, and then you have a weapon failure.

So the piston guns dump the heat outside the action not in the action and the bolt never gets very hot.
Problem solved!
For FULL AUTO!

Note; such a system does NOTHING to keep sand from getting between the bolt and the receiver, so the idea that it’s “better” in the sand is not really true.
You still need to lube them. And lube does attract sand. And the lube will burn off on full auto guns a LOT faster than it does in Semi-auto fire.
So again, the piston gun is a great answer to the problem……IN FULL AUTO!

In Semi autos you CANNOT get the bolt hot enough to soften it without having a LOT of loaded mags, a lot of ammo and a very small brain.

According to the tests we did in Nevada in 2004, firing 10 mags as fast as you could load and shoot an AR-15 (semi-auto of course) in the heat of the day, (in june) and then taking an infrared heat reading on the bolt carrier we found we could not get the bolt and carrier any hotter than 465 degrees. But 4 mags fired full auto in an M-16 got the heat up to 925.
925 will anneal most alloys of steel. 465 will not.

So I make my statement again, that for semi-auto guns the piston is not bad, but it is not doing anything of real value for you that the DI doesn’t do as well.

Also the DI system can be made into a more accurate gun than the piston system just because you can’t totally free-float a piston gun.

Ok……
Your turn.
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Old November 14, 2012, 04:57 PM   #13
TMD
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One nice feature on Rugers SR556 and some other piston driven models is the selectable gas block that allows you to turn it off and make the gun a single shot. Sounds silly unless your running a suppressor then it kind of makes sence.
Now if I could just get my hands on one of Rugers piston systems for my .300 BO
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Old November 14, 2012, 08:09 PM   #14
buckhorn_cortez
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Quote:
If you want a piston AR go with Ruger. I think it’s the best value for such a gun on the market and they are pretty close to 100% trouble free.

However I would point out a fact to you and the readership.

In semi-auto guns the piston is a perfect answer to a non-existent problem.
The thing that has caused failures in the M-16 family of rifles and carbine in the US Military’s action is heat. The idea is not valid that the “cleaner piston guns” make them work in sand better. They don’t

The heat from the Stoner system dumps on top of the bolt from the gas key in the carrier. The bolt heats up in full auto fire and in some actions, the amount of FA fire is enough to get the bolt over 900 degrees. I have heard from some folk in Va that it can go even hotter in some cases.
If you take steel and heat it quickly and cool it slowly, and if you do it enough times, you can soften the steel. It’s called annealing.

So, the bolt body gets hot. It cools slowly. It’s hot right where it’s the thinnest, at the cam pin hole. If that gets a bit soft it can elongate in use. Only a few thousandths is enough to make the pin “slap” back and forth as it locks and unlocks. As that continues you see cracks develop at the pin hole. After time the crack can turn into a break, and then you have a weapon failure.

So the piston guns dump the heat outside the action not in the action and the bolt never gets very hot.
Problem solved!
For FULL AUTO!

Note; such a system does NOTHING to keep sand from getting between the bolt and the receiver, so the idea that it’s “better” in the sand is not really true.
You still need to lube them. And lube does attract sand. And the lube will burn off on full auto guns a LOT faster than it does in Semi-auto fire.
So again, the piston gun is a great answer to the problem……IN FULL AUTO!

In Semi autos you CANNOT get the bolt hot enough to soften it without having a LOT of loaded mags, a lot of ammo and a very small brain.

According to the tests we did in Nevada in 2004, firing 10 mags as fast as you could load and shoot an AR-15 (semi-auto of course) in the heat of the day, (in june) and then taking an infrared heat reading on the bolt carrier we found we could not get the bolt and carrier any hotter than 465 degrees. But 4 mags fired full auto in an M-16 got the heat up to 925.
925 will anneal most alloys of steel. 465 will not.

So I make my statement again, that for semi-auto guns the piston is not bad, but it is not doing anything of real value for you that the DI doesn’t do as well.

Also the DI system can be made into a more accurate gun than the piston system just because you can’t totally free-float a piston gun.

Ok……
Your turn.
My turn? You protest too much.

I have a question. You used a non-contact infrared thermometer - did it have an adjustment on it for emissivity? Without the correct emissivity adjustment, you can be 10 F or more off in temperature measurement. Did you adjust the thermometer to the correct emissivity for the surfaces you were measuring?

As for accuracy, I don't consider the AR15 an especially precision rifle. That being said, a friend and I were shooting my REC7 at steel plates using my shooting bag as the rest, and hitting an 8-inch steel plate at 300 yards quite easily.

When I sighted in the scope on the gun, I used the 100 yard tunnel at my gun range to eliminate cross wind problems. The REC7 shot two 5 shot, 3/4-inch groups - I don't need better accuracy than that out of an AR15.

BTW - lubrication cannot "attract sand." It can certainly hold dust, and dirt -but attract it? No. One thing on the Barrett. The bolt is NP3 coated and the gun needs minimal lubrication. I live in New Mexico - it's always dusty, especially on windy days. I use minimal lubrication on REC7 as the gun really doesn't need much. In fact, I haven't lubricated the bolt in the last 1,000 rounds.

There is one advantage to a piston gun even in semi-auto rifles. If you use a supressor on the rifle, a DI rifle requires more lubrication as a larger amount of gas is directed back through the gas tube by the supressor. It is also possible to over gas a DI gun with a supressor. Those problems cannot happen in a piston gun.

The Barrett has a second valve position on the gas block for use with a suppressor and vents more gas out through the block. Without the supressor, the normal gas block setting is self-regulating and does not require an adjustment to run with any type of ammunition.
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Old November 15, 2012, 02:54 AM   #15
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Quote:
Wyosmith posted:
Also the DI system can be made into a more accurate gun than the piston system just because you can’t totally free-float a piston gun.
You're right that the DI system has the potential to be more accurate, but a DI gun can't be totally free-floated any more than a piston can; they both have a gas port and something that connects that gas port to the upper receiver.

Quote:
buckhorn_cortez posted:
There is one advantage to a piston gun even in semi-auto rifles. If you use a supressor on the rifle, a DI rifle requires more lubrication as a larger amount of gas is directed back through the gas tube by the supressor. It is also possible to over gas a DI gun with a supressor. Those problems cannot happen in a piston gun.
If you have issues with getting gas in your face when using a DI gun with a suppressor, just switch to a heavier buffer. On the other hand, a suppressor is usually quieter on a DI system because with a piston there are hot, loud gases being vented near the gas port.
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Old November 15, 2012, 04:55 PM   #16
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Read up some reviews of the PWS MK116 before you make your decision.
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Old November 15, 2012, 07:01 PM   #17
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On the other hand, a suppressor is usually quieter on a DI system because with a piston there are hot, loud gases being vented near the gas port.
I 2nd this.

It is noticeably more quiet, even to the "naked ear".
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Old November 15, 2012, 07:12 PM   #18
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If you have issues with getting gas in your face when using a DI gun with a suppressor, just switch to a heavier buffer. On the other hand, a suppressor is usually quieter on a DI system because with a piston there are hot, loud gases being vented near the gas port.
True story. A H3 buffer does wonders to eliminate gas in the face, and a full auto bolt carrier and better charging handle will help as well (BCM Gunfighter or PRI Gasbuster for example). And for those who really want to address the gas concern, there are plenty of adjustable gas block options out there that will allow you to tune the gas on a DI system. So I'm not sure that a piston gun has any distinct advantage here.

I'll add too that as an 07/02 FFL who shoots lot of full auto guns, I'm not sure a piston gun has much advantage over a DI even in sustained automatic fire. The kind of sustained fire required to heat internal components to the point of damage that some have suggested is going to wear out other parts of the system anyway, so that if you're really dumping mags at that rate of fire you're going to run into other problems beyond the BCG. We've seen for example barrels shot out and fire control groups broken, either of which can and do happen on piston guns as well. One of our AK's developed such a problem with trigger pins walking out after time that we had to finally weld it in place, a problem that came about directly as a result of sustained automatic fire.

The point is that automatic fire puts a level of stress on the entire weapon system that is going to cause unique problems regardless of whether it's a piston or DI system. Knowing that, we prefer to run DI guns since access to parts and ability to repair them is much easier and cheaper than any of the piston systems.
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Old November 16, 2012, 09:02 AM   #19
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So I'm not sure that a piston gun has any distinct advantage here.
The big advantage with the piston system is the fixed expansion chamber/piston dimensions that remain irrespective of barrel lengths.

So you can swap out barrel lengths/uppers without needing to "tune" the gun to run with different gas pressure inputs. It is always the same, assuming you keep the required inlet pressure coming into the piston from the barrel. (You "should" be able to run a 20" upper and a 10.5" upper on the same lower without having to fiddle with the buffer.)

There is also the improved "over the beach" performance. But since most civilians aren't going to be swimming into an objective and popping up out of the water and "going hot" without having time to let the water out of the gas system it is kind of a moot point.

The biggest advantage I could see in fullauto is that it would require less lube to be added during a high volume shooting string since the piston won't be blowing lube out.

In my experience, when it comes to shooting suppressed, I can't visually see a difference between the amount of crud the gets blown back into the action due to the suppressor between a piston and a DI gun. Both absolutely cover the inside of the gun/cartridge stack with soot.

If you need any help wringing out any of those full auto guns, let me know, I would sacrifice some of by valuable time helping you turn cartridges into noise.
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Old November 16, 2012, 09:42 AM   #20
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Hello, I'm hoping for some input on a new AR buy. I'm in the market for a new AR in the 16" barrel length. I have narrowed it down to the Ruger SR556 and Sig 516.
before you go with the Ruger or SIG, look into this one, i own three (3) LWRCI piston carbines they are as accurate as any DI guns, in fact this company was the first to introduce the AR piston system.., then all the other AR makers had to jump into the piston craze with their versions some are good others are crappy. i believe the M6A2 is the best of them all..., just my OPINION !!

http://www.lwrci.com/p-4-m6a2.aspx#inf-tabs
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Old November 16, 2012, 02:55 PM   #21
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If you need any help wringing out any of those full auto guns, let me know, I would sacrifice some of by valuable time helping you turn cartridges into noise.
If you make ever it out to Eastern Washington then you let me know and I'll make sure to take you up on your offer to "help". There is no greater joy than putting a full-auto rifle in someone's hands and seeing the smile it creates.
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Old November 16, 2012, 03:27 PM   #22
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If you make ever it out to Eastern Washington then you let me know and I'll make sure to take you up on your offer to "help". There is no greater joy than putting a full-auto rifle in someone's hands and seeing the smile it creates.
Dang. I was hoping you might at least be on this side of the Mississippi.

But the company I work for does have a facility in Eastern Oregon. Maybe I might need to go for a visit and take a detour.

I agree with you about full auto.

I wish I could afford a MP5. It was the most fun I have ever had shooting a gun.
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Old November 16, 2012, 03:53 PM   #23
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Dang. I was hoping you might at least be on this side of the Mississippi.
I might actually be headed your direction this Spring. One of my business partners is scheduled for deployment within the next year, and we were talking about heading to take a class at Tactical Response in Camden before he leaves. So if we make it out there I'll be sure to let you know.
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Old November 16, 2012, 05:20 PM   #24
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I might actually be headed your direction this Spring. One of my business partners is scheduled for deployment within the next year, and we were talking about heading to take a class at Tactical Response in Camden before he leaves. So if we make it out there I'll be sure to let you know.
SWEET!

I have taken a class from James and I grew up just down the road from Camden.

James has a few Class III weapons himself. He offers a nice AK operators course that uses converted AKs. If you take that class you can use one of his AK's in his Fighting Rifle courses.

A lot of people don't like him, but he is a very good teacher if you get past his gruff exterior. He really helped my wife with some stuff that I couldn't teach her. (She wouldn't listen to me.)
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Old November 16, 2012, 05:56 PM   #25
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He really helped my wife with some stuff that I couldn't teach her. (She wouldn't listen to me.)
I have a wife and four children like that too...
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