Just my opinion but there is nothing wrong with either system and they both have their advantages and disadvantages. Pick your poison.

The only thing I will say is in agreement from JaPes, buy it from the factory if you go piston. "Upgrade" kits do not work well and if they do work, won't work well for as long as a designed from the ground up rifle.


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"I once was blind, but now I see."

Stoner also included a chrome chamber in his design, but McNamara decided that "they don't need chrome on their guns." That, added to the jamming caused by DI fouling, helped add to the list of names on the Black Wall over by the Lincoln Memorial Meanwhile, the enemy pressed on with their choice of infantry weapons, along with 60 million others that will run like a battery bunny. Have you seen the video on the tube of the guy who runs an AK until the furniture ignites-and continues...?

I appreciate everyone's opinion.

Sorta kinda Looking at the Ruger SR 556 but I'm not familiar with the two-stage piston.

Has anyone had any experience with the two-stage piston?

Gunsumerreports.com has a review of the rifle but it's dated 2010.

What you have in the SR 556 in a nutshell.

1. Round fires.
2. Combustion gasses travel down barrel.
3. A portion of the gasses is diverted from the barrel to the adjustable gas regulator.
4. The gasses exert force on a small gas piston.
5. That force is transferred to a transfer rod.
6. The transfer rod impacts the key on the top of the bolt
7. The the impact cycles the bolt.

If you want a SR-556 go for it. If anything goes wrong, call Ruger. Their CS is excellent.

__________________
-John

Funny that this thread should be resurrected. I was at the small gun store today. Someone made the shop owner an offer he couldn't refuse on his personal AR-15. He needed one ready just in case he wanted to shoot. He assembled one:

• H&K 416 complete upper kit including the H&K buffer and buffer spring.
• LMT Lower
• Geissele Trigger
• Remington Defense free float fore end
• Sopmod Stock
• An LMT rubberized grip. I honestly don't know which one.

He didn't mess with installing an Osprey Defense gas piston conversion or anything of the sort. He chose a complete H&K upper kit with H&K buffer and spring to build a piston driven AR-15. Impressive rifle. If I could build one at dealer parts cost, I still wouldn't. If I ante in that much dough, I'll just save up more and buy a factory complete H&K 416. Once I had that money, I still wouldn't do it. I'd probably buy a SCAR 16 or go .308 with the SCAR 17 Heavy.

I guess my point with gas piston driven AR-15's is that the gas piston system adds cost and weight to the rifle. While there are benefits from a gas piston system in an AR-15, it comes at an increased cost. If you want a reliable gas piston driven AR-15, you need a factory complete AR-15 (or H&K complete upper + buffer & spring kit). I whine and moan about cleaning. Yes, a DI AR-15 poops where it eats. Yes, it can be a chore to clean and get 100% spic and span. Yes a piston system runs cleaner... but you pay a cost for it.

Ruger SR-556 Takedown (the only SR-556 currently listed on the Ruger website) = MSRP $2,199

Ruger AR-556 (traditional DI) = MSRP $799.99

The$1,400 cost difference between the two to have a piston driven AR-15 from Ruger is a punch in the nuts. Will the average guy who wants to shoot an AR-15 on the range need a piston? No. Would the guy who wants to take an AR-15 carbine class or two need a piston? No. The rationale employed for many AR-15 purchases is for self defense during a Red Dawn, poop hits the fan, world without rule of law calamity. Will the increased complexity of a piston driven AR-15 be of use? In my opinion, no. Complexity adds probable failure points. A piston isn't native to the AR-15, so adding a piston is adding complexity.

The individual with money in hand has to weigh all the pro's and cons to decide for themselves.

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-John

Exactly. I want the newbies to understand I'm no expert. I'm giving my free opinion, so treat it for what it's worth.

By the time I burn another 6,000 rounds through my Tavor and need to replace the barrel, do you think I'm going to be happy about it? No. There is a single source for replacing the barrel, IWI US. Since it's a single source part, I'm have no choice but to pay whatever they want for it. I'll most likely have to send in the firearm for them to install it. This is increased total cost of ownership.

Newbies have to think about this. By the time an AR-15 owner has to replace a barrel, they can buy a good barrel and install it themselves. That is a total cost of ownership cost savings.

These are things to consider when choosing a rifle.

Bingo. I own a Tavor and a Russian AK-M (made at the Izevesk Mother Plant). My current preferences for a long stroke are due to what I happen to own. I'm sure I'll change my mined whenever I get around to buying a SCAR.

__________________
-John

If you have to have piston rather than direct impingement for cleaning purposes, then get something besides a conversion kit for your AR, or any AR built with a conversion kit, such as the now-discontinued S&W.

The bolt and bolt carrier do extensive damage to the receiver over time, and the only rifle that does not experience this is the Colt LE6940P, with its unique articulating link piston system, which allows for the deflection caused when the gas piston strikes the top of an ordinary bolt carrier, which causes it to nose dive as it goes rearward, which eventually creates a non-repairable gouge in the receiver. So, get the 6940P from Colt, or get something besides an AR platform if you have to have a piston, rather than direct impingement.

Poops where it eats? Yeah, I've heard this before. It's not true, but I understand the comparison.

Yes, the bolt carrier gets dirty, but that's just part of gun ownership. I don't find it difficult to clean. If you clean it every 500 rounds or so, it's easy enough and will keep running just fine. At the last class I went to I fired about 650 rounds without cleaning and never had an issue. I don't imagine I'll be shooting more than that at one go.

My ARs are fine as is. I'll stick with the Mini-14 if I want a piston gun.

__________________
Freedom isn't free.

It's absolutely true. Some AR-15 owners don't like to acknowledge the weakness of the system.

Hot dirty combustion gasses are redirected into the action to act against the bolt/carrier to cycle the action. It poops where it eats. My piston driven rifles impart the energy to cycle the action onto a piston. The piston gets dirty sparing the action from hot dirty combustion gasses. It doesn't poop where it eats.

As I've said, the AR-15 is supposed to be DI. Less complexity, less parts, less to go wrong, less to troubleshoot, lower weight. With standard furniture, an A2 Front sight post, and a stock combat trigger an AR-15 that meets the minimum mil-spec as civilians can legally possess will be darn reliable. They can take more punishment than the average civilian owner is willing to put one through.

Sure. I've run 700 rounds through my AR-15. Cleaning is cleaning. I devoted a thread to all the tools I've used to clean one. Break out the CAT M4 tool to scrape the bolt tail, chamber brush, solvents, swab out the upper, blow out the lower, swab out the buffer tube. Why? The AR-15 throws junk back into it's action.

My long stroke gas piston systems are just as simple as a DI AR-15, but they pay a little bit of a weight penalty. What do I get in return? Carbon fouling concentrates to the tip of a piston. Action stays clean and runs cooler. Chambers are inspected, rarely fouled beyond needing a quick swab out.

For me to get this, I pay a penalty in other aspects. It's a give and take.

__________________
-John

I weighed the +/- of converting to a piston system and dismissed the idea. However, I did install an adjustable gas block. Significant difference in the operation of the rifle and my shooting. Big +.

Not it is not.

Watch a slow motion video of the right side of an AR being fired. See that big puff of smoke coming out of the ejection port? That is your hot dirty gasses being vented from the action by way of the two holes in the side of the bolt carrier and out of the action through the ejection port.

Side note: If you're getting excessive build up in the bolt carrier perhaps you should try better quality ammunition or a cleaner burning powder in your reloads.

I have a few direct impingement ar15's and I have finally ventured into piston AR's with the purchase of a 16 inch Huldra 5.45x39 piston upper M4 barrel profile(basically an Adams Arms piston system) a while back.

I don't believe that the argument that piston setups are heavier than direct gas impingement rifles/carbines is that valid any more, of course it may depend on the particular manufacturer. This Huldra upper subjectively feels no heavier than my direct impingement uppers, including my Smith & Wesson MP15A and MP15 OR rifles.

Additionally, I have a friend that recently got a LWRC upper with the spiral cut heavy barrel and surprisingly it was really well balanced and did not feel as heavy or any heavier than my my direct impingement Rock River upper with a heavy profile barrel.

I don't know why we can't like both, piston and direct gas systems. I know I like both. I guess time will tell, if the longevity of the piston system will match that of the direct gas impingement system.

I have no preference with either system myself. I have firearms with both. Weight would depend on the design. With the extra metal in the piston system from the piston and the operating rod, it would have to be at least a little heavier but I'm sure that can be compensated for in other ways like a lighter barrel. I like both and don't have any issues with getting a firearm with either system.


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Thank you for your service and I agree. No need to change if it has DI. I have both and both work well.