PDA

View Full Version : AR Question: Gas tube vs. Gas Piston


Sirius
03-18-2007, 4:49 PM
I'm thinking of purchasing a gas piston upper for my AR. I read where they are more reliable, (ie cleaner, cooler running) than the traditional gas tube system. I know the design has been around for a while, but they don't seem to be catching on with the AR crowd. I also read where they may not be as accurate as a gas-tube system because of the piston's moving parts but the difference is relatively small.

Thoughts on gas-piston uppers besides being a bit pricey - thanks!

xenophobe
03-18-2007, 4:55 PM
You should search ar15.com. The subject has been beaten to death multiple times...

bwiese
03-18-2007, 5:04 PM
I'm thinking of purchasing a gas piston upper for my AR. I read where they are more reliable, (ie cleaner, cooler running) than the traditional gas tube system. I know the design has been around for a while, but they don't seem to be catching on with the AR crowd. I also read where they may not be as accurate as a gas-tube system because of the piston's moving parts but the difference is relatively small.

Thoughts on gas-piston uppers besides being a bit pricey - thanks!


For most everyone's purposes - esp of a citizen or LEO - a standard AR gas system will serve them fine.

All these specialty vendors need is something 'new' and 'different' to sell to separate them from the herd, the latter of which sell regular ARs that work perfectly fine (with exception of low quality 'bottom feeder' vendors with lousy or Chinese parts, etc. - think ASA, Model 1, Oly Arms...)

Some or many of these vendors may or may not be in business down the line, and all of their systems are different/incompatible as far as replacement parts. [If anyone has a chance over long term, it's probably Colt's LE 1020 system.]

Accuracy of piston ARs may or may not be reduced - depends what rattles around, how much it can move, and if it's moving at all during the time the bullet's fired and/or in the barrel. One of the reasons the traditional AR design is so accurate is this lack of extra moving parts (gas piston) and the fact the multilugged bolt locks/unlocks by rotating only a few degrees, instead of the massive semicircular rotation typical semiauto bolts undergo.

For the price of one typical piston AR upper you could buy 2.5 - 3 quality regular uppers. Even the ARES piston kit costs a fair fraction of what a barreled upper receiver (minus bolt/carrier) costs.

These uppers may have very limited usefulness to the limited set of folks in desert climes w/o time to clean their rifles fully and with reasonable frequency. There's also not been much info other than marketing-oriented statements that these added parts do not add their own failure modes: that is, they may improve or 'fix' one thing but introduce a new set of failures elsewhere. That won't be determined til a large fraction of such piston rifles are in service, and unbiased long-term stats from a non-vendor can be accumlated and analyzed. This latter stuff hasn't happened, and likely won't, given that piston ARs have only been acquired in small-unit quantities for very restricted distribution. All rifles jam if you get enough dust/dirt/crap in them.

I shoot a lot of ARs, even w/dirty ammo, and can clean my AR in ~ 3 mins (maybe 5 if it's really really grimy from Wolf ammo, and picked up some dust & loose cat litter from the bed of my truck). Never had a problem.

Use a chrome-lined barrel (and chamber), scrub your chamber with the brush, keep your AR well-lubed w/CLP or BreakFree as per the USGI user's + tech manuals available on AR15.COM and you'll have reliable accurate rifles without any frou-frou of specialty parts availability concerns or wildly overpriced stuff that's essentially semicustom.

Noobs getting ARs should stick to stock configurations.

fun2none
03-18-2007, 5:56 PM
Spend the money on an SDMR or Mk12 upper instead.

As Bwiese so well summarized, there is not much to be gained with a semi-auto gas piston AR.

Also, keep in mind that AR gas piston designs are proprietary. If a critical part needs to be replaced you are at the mercy of the original manufacturer, if they are still around. There are no after-market milspec replacement parts for the gas piston components.

Then again, if money is not an issue, the heart wants what the heart desires.

bwiese
03-18-2007, 5:58 PM
Then again, if money is not an issue, the heart wants what the heart desires.

That's what I said when I got my Rolex, or when I go to a nice steakhouse :)

I think the orig poster would be best served getting a nice upper (or two!) and a good quality optic for his application (ACOG? Leupold? Valdada?) as a more optimal use on funds he apparently might have as 'disposable'.