Gas Pistons in an AR15 - is it worth the extra money

[misunderstood]

been looking at ar15 for a little while. i have noticed that gas piston design can run you little more on price. is the gas psiton worth the extra money?

[lukem]

I recently upgraded my Bushmaster Patrolman M4 to an Osprey Defense Gas Piston with a FailZero coating. I had some problems with it chambering rounds before, probably due to the ammo I was using and just wanted to upgrade to a piston to see if that would help. I'm still in the "trying it out" phase. After installing it I had to send my upper to Osprey to check out since it was firing but not chambering the next round. They fixed it and it was due to something with the pin hole in the front sight mount. I just got it back and just need to take it to the range but they said they put about 100 rounds through it and it was running like a sewing machine.

I want to add that I think Osprey customer service is TOP NOTCH. Joseph Scimeca tried to resolve the issue over the phone with me but then just said to send it in and they'll take a look at it for free. All it cost me was freight there and they paid for it to get back to me. I can't wait to get out and shoot it.

[SGB]

The Gas piston makes sense in guns using extensive full auto use, for the average AR there is no benefit. My .02

[Wyldekard]

Go to YouTube and search for a comparison. There is a theory that a gas piston AR is less accurate. I watched one comparison that was well performed and it helped me decide if the extra money was worth parting with. I decided the money would be better spent on ammunition.

[bwegner]

There is a theory that a gas piston AR is less accurate.

I advocate gas piston rifles but this is more than a theory. ALL ELSE BEING EQUAL....a moving piston as a bullet is rolling through a barrel does can cause some inconsistent vibrations (harmonics) with the piston which can affect accuracy. Much of that can be mitigated with either a thicker barrel or a lighter piston. The difference is only dramatic depending upon the length and weight of the piston. A good example are gun like the AK which have long op rods.

Patrick Sweeney has a good article on this here AR-15: Piston Pros & Cons - TACTICAL GEAR

So why do I still prefer most gas piston rifles?

1) Most are far easier to clean [ever try cleaning a DI tube vs. a piston say every 5k rounds; it's easier to just replace the tube rather than clean it/ cleaner chamber/ cleaner bolt etc],
2) Have far less heat in the chamber and on the bolt which change the properties of the smokeless powder - usually by heating it up and increasing muzzle velocity shot-to-shot thereby ruining consistency under rapid fire conditions (not just full-auto). That said both DI & GP gun barrels will heat up and that will change the POI regardless (barrel droop),
3) Generally requires less lubrication since it doesn't cook it off lube like DI guns do (DI guns love lube but some conditions like sand and fine grit may play havoc with more lube),
4) I have found most gas piston guns to be more reliable in less than optimal conditions. That doesn't mean DI are not reliable, they just aren't AS reliable (everything else being equal) unless conditions are closer to optimal.

All that said, I would buy a DI rifle with good engineering over a GP rifle with so-so engineering. The quality of the build is generally most important in getting both accuracy and reliability out of a gun.

[dave606]

You will really appreciate having a piston rifle the first time you get home from a long day of shooting and have to clean your rifle. I always keep my AR's really clean and the BCG is the most time consuming part. When i got home with my first piston rifle AR after a day of shooting and opened the rifle and examined the BCG i knew this was for me. I still shoot both without any problems but find when going to the range i will grab a piston model more times than not. Cleaning the piston is much less time consuming. You also gain the ability to fine tune easily.

[Sheldon]

I have often wondered about this, the pros and cons to a gas piston vs gas tube....

[smith934]

Go to YouTube and search for a comparison. There is a theory that a gas piston AR is less accurate. I watched one comparison that was well performed and it helped me decide if the extra money was worth parting with. I decided the money would be better spent on ammunition.

DI ARs get a bad rap vs. GP rifles when it comes to reliability. Pat Rogers has had a couple of articles in SWAT about rifles that he has used in classes that have gone 1,000s of rounds with minimum cleaning and keeping them 'wet'. Personally, I hate cleaning and on my AR's I do a minimum amount of it, but i do run them wet and use quality ammo.

As far as accuracy goes, I don't shoot GP ARs but I do own a SCAR and it is very accurate.

Bottom line for me is go with a top tier manufacturer, use good ammo, and run it wet.

[6shootercarry]

It really depends on what you plan to do with it... For the weekend range trip, gas is the way to go. Get more ammo and shoot more... As indicated above, keep the rifle wet (lubed). Slip 2000 Gun lube and EWL work well along with M-Pro 7 products. In fact, the article in the SWAT magazine was about the Filthy 14. The rifle is a gas impingement AR-15 built by Bravo Company Mfg that went 36,000 rounds (and counting) with no cleaning or break down other than removal of the BCG for lube. The oil used was Slip 2000 EWL.. I have 2 Colt AR-15 gas impingement rifles and have had no problems.. Buy a good rifle such as the Colt, Bravo Company Mfg, Daniel Defense etc.. And get lots of ammo and enjoy it.. If later you decide to upgrade, buy a piston upper.. Now you have both... ADCOR makes a B.E.A.R piston upper that has been Mil-Spec tested and passed with flying colors.. Performance is a question of $$. How much do you want it to do?

My 2 pennies..

[Danny Stanley]

One common theme everyone seems to repeat is that the piston system is cleaner or at least easier to clean. I would argue that it is no cleaner than a DI system, it just moves the dirt elsewhere. If you think cleaning the powder residue from inside the receiver is a pain, try cleaning it out from under the floating handguards. I'm sure if you have standard handguards that are removable then it is easy enough, but if you have to remove a barrel nut or a series of allen screws to clean it, has it really made life easier? Also, take a close look at how the DI system operates. When the gas enters the carrier key it imparts force on the bolt rings and pushes the bolt forward slightly while pushing the carrier rearward. This reduces the friction between the bolt lugs and the barrel extension lugs. I have not seen the long-term effects of a piston system, but I would expect to see wear on the locking lugs, cracked lugs and premature headspace issues due to the excessive force from the bolt being ripped from the locked position. I have also never seen any issues with having to clean or replace the gas tube on a frequent basis. I have been repairing and rebuilding M16/M4's for the Army for years as a contractor, and I only replace them when I replace the barrel, they last forever. I'm also in the reserves, and I can tell you I have had the same gas tube on my issued M16A2 for over ten years and it has never failed to function. My personal AR15 has had the same gas tube for close to ten years also.

I think everyone gets too hung up on cleaning. I rarely clean mine, and it functions fine. I know I am required to clean the one I'm issued at my reserve unit, but I do so at the bare minimum. Just enough to get the chunks off, and back to the range I go. I have never had a jam or misfeed. Lubrication in the right places is the key to success.