View Full Version : Question about Piston Operated AR?

02-20-2007, 5:55 PM
Hey Bros,

Iím thinking about purchasing a piston operated AR upper from LWRC or P.O.F, just wondering if anybody has one of these uppers and if so, what's your opinion about them.

Also, any reviews and comments about piston operated uppers in general would be greatly appreciated, basically are piston uppers worth the price?

02-20-2007, 6:28 PM
Short answer version of very long answer to question.
Not worth it unless you plan on using it for something serious (ie you are a LEO, contractor, putting it on a reg AW, etc...)IMO.

Long answer. I love these things!! They are PERFECT for any heavy duty LE or military performance situations. They run COOL, CLEAN and REILABLY. I have tested them and lusted after them on both class III and semi receivers since they first showed up at LE shows.

They incorporate the durability of the AK system (if you use the right mag with them) and the adaptable nature of the AR type platform.

I think it might be a sin against god or something to put it on a OLL receiver if you are running a fixed mag build IMO. This kit was designed as a work horse under heavy use in all variety of conditions.

A fixed mag build requires that you open the rifle to reload. Heavy carbon fowling in the receiver will be evident when you open the gun. The standard gas system AR upper will be more than enough for this type of build. Just check out all of the people who have built them here and had astounding results from them. You can buy 2 normal complete uppers (if you shop around)for the cost of a complete POF upper. Spen your money on a second caliber or something instead.

But, hey...its your money and god knows you spent the time earning it. Spend it how you want.

Edit: Sorry if I offended anybody here who has a POF upper on their fixed mag build.

02-20-2007, 6:32 PM
There is little need for most mere mortals, including LEOs and soldiers, for a piston setup. 40 yrs of AR evolution has resulted in a tough reliable system.

This is just "something new to sell".

There have been no real longterm wear reports, etc. If you buy one system you are at the mercy of the vendor's survival, as parts are not standardized like regular AR parts. The only vendor that might be around for awhile would be the Colt LE1080 setup.

02-20-2007, 6:56 PM
I have a pof upper and i am real happy with it clean and reliable

02-20-2007, 7:02 PM
Leitner-Wise, so far, has the simplest and most creative design. ARES drop in system would have to be a close second. The POF is an older implementation, is larger, but has been tuned to near perfection. HK is still unavailable to the civilian market, and Colt has not met repetitive timelines, though once it comes out, it may prove to be a new standard.

Out of the gas-piston uppers currently made, the LW is by far the best system, though it is probably the most expensive available.

Time will tell, but the gas piston AR is here to stay. The XM-8, the HK P416, the FN SCAR, the Robinson XCR and Magpul Masada are all gas piston systems, and there is a valid reason why all these newer systems have them.

02-20-2007, 7:06 PM
I agree with Mike... The LW has the simplest design. If you want, PM me for a a pic of the LW DMR. I am waiting on Darren to give me the price on the replacement parts that I will need in the future.

02-20-2007, 8:52 PM
Anyone ever made a gas-piston AR (consistantly) shoot less than 1MOA?

02-20-2007, 8:54 PM
Thats a good question since non of the mfgs. claim a sub MOA AR.... Unless someone can point me to that claim....:confused:

02-20-2007, 9:15 PM
Anyone ever made a gas-piston AR (consistantly) shoot less than 1MOA?

Nobody has proven that the gas-system upgrade to a gas impingement system affects accuracy.

02-20-2007, 9:21 PM
Reviewed most of all the pamphlets I have received from LW, BM, and Colt. They all stated "improved reliability". Nothing about accuracy.

02-20-2007, 10:24 PM
All of the ones I have played with were 16 in or shorter types. This thing really comes into its own reliability wise when you get it down bellow 14 inches in length.

Accuracy with the 16 in POF was about the same as my 16 in Bushmaster Vmatch upper. Not bad for hte intended goal of the product. I have no idea about longer range. I have never played wiht it at distances longer than 50 yards. I'm sure those that have them here can chime in with their experiences with that.

02-21-2007, 7:56 PM
Bushmaster is also selling an AR gas piston upper.

02-21-2007, 11:58 PM
Gas-piston in general does not make for a terribly accurate firearm. Too much moving too soon.

Direct-impingement has the advantage of the action usually barely even seeing a pulse wave untill the bullet has left the barrel.

02-22-2007, 12:06 AM
Gas-piston in general does not make for a terribly accurate firearm. Too much moving too soon.

Direct-impingement has the advantage of the action usually barely even seeing a pulse wave untill the bullet has left the barrel.

In theory. In application is hasn't been proven.

02-22-2007, 6:22 AM
The AR15 is a gas piston rifle.

However, the gas piston is located in the bolt carrier group, with the gas routed to it via the gas tube.

Locating the piston behind the bolt is the ideal location for the piston to operate, from a mechanical viewpoint.

It does create a situation with the gas leaving carbon residue in the area, which mixes with lubrication to make some gunk. This appears to be the main reason why people want to change, from most of the posting that I read on the subject.

However, moving the gas piston above the barrel, and using an op-rod to connect to the carrier introduces another set of issues to contend with.
So, pick your own poison.

IMO, the AR with the Stoner Gas System as employed for over 40 years has the best set of pros and cons that I've yet seen. Sure, it gets messy after a while if you don't clean it. But the in-line operating system, causing all firing and recoil forces to be in a single line that is axial to the boreline, is virtually ideal mechanically.

Just as an aside, the overhead piston is not what makes an AK "reliable", so any references to "AK reliability and AR accuracy" are just misplaced. The loose clearances, and places inside the receiver for dirt to fall away from the action, are what makes the AK work in dirty conditions.
And technically speaking from a design viewpoint, the reciprocating mass above the boreline in an overhead piston-operated gun can have effects on accuracy and controllability, depending upon the way the piston and op-rod are designed and implemented. No doubt, all the overhead piston system makers are doing whatever they can to minimize this.

I'd change to an overhead piston and op-rod, IF I were using the gun in a full-auto LMG role, with long belts of ammo being expended in a single burst.
Other than that, I don't see any advantages to changing to an overhead piston.