[xdm11chad]

There is 2 different upper types piston I think and gas? Please if that is right explain the difference for me, I'm about to drop $650.00 on a Adams Arms 16" piston upper

[purehavoc]

Piston and direct impingment. The piston setup is a little cleaner. The bads. Not as reliable and heavier.

[USEBOTHHANDS]

supposedly the piston drive is ALOT cleaner, runs WAY COOLER, and runs MORE reliably. the weight difference, from what i've read, is between 0.0 and 5.0 oz (about 1/4lb to 1/3lb). the AK is a piston drive.

[AgentTikki]

http://www.firearmstalk.com/forums/f20/ar15-primer-beginners-guide-59600/

*Gas Systems.*

There are 2 major types of gas systems that the AR runs on. The first being DI (direct impingement) and the second being piston. DI is the original design. Piston is a relatively new development. There have been forays into piston designs in the past, but it’s only been recently that piston driven ARs have been become popular. The best thing I can do you is show you the pros and cons a piston system offers, it’s your personal choice to decide if it fits your needs. Please understand that since there is no set standard for a piston system, every piston system is a proprietary design that will require different and non interchangeable parts.*

Pros:
*A cleaner running system. (less fouling of the BCG and chamber, more fouling by the gas block or exhaust)
*Should be more reliable in adverse shooting environments.
*Should be easier to clean, (provided you don’t need to remove the hand guards)

Cons:
*Costs more than a comparable DI setup
*Weighs more than a comparable DI setup
*Harsher recoil impulse (I concede that this is subjective and debatable)
*Inherently less accurate,(minor)
*Slower follow up shots (minor)
*Proprietary parts make it harder, costlier, and longer to replace broken parts.

Personally, I would only recommend a piston setup if you where looking for a non precision type carbine and need the extra reliability due to your expected shooting environment.

DI gas systems come in 4 flavors: Rifle, mid-length (middy), carbine, and pistol. The most common types are carbines, with 7” handguards. The next most common types are rifles with 12” of rail. Relatively new developments are midlengths with 9” handguards. Pistols are uncommon and I won’t be going too much into them. Only consider rifle length gas systems for 18+ inch barrels. Both carbine and midlength gas systems can be used for 14” to 16” length barrels. For these lengths, I usually recommend midlengths as their advantages outweigh their disadvantages:

[JonM]

One thing i want to make note of. Gas pistons do NOT run cooler than di guns. They are the same. The laws of thermodynamics arent suspended just because you slap a piston on a gun. The heat goes somewhere. Its just whether you want to heat up the gas tube or the piston block.

Since it takes over 50 magazines at full auto non stop to blow up a gas tube or a piston its a non factor.

My experience with gas piston is the bolt runs cleaner but you cant run it dry anymore than you can run an m1a or m1 garand dry. You have to use lube. Gun oil such as rem oil or clp are extremely poor lubes regardless of design. My choice is 30weight motor oil. With a di gun generous usage of motor oil prevents junk being caked on and a simple wipe with a cloth is all thats needed to clean the innards.

[USEBOTHHANDS]

Originally Posted by JonM

One thing i want to make note of. Gas pistons do NOT run cooler than di guns. They are the same. The laws of thermodynamics arent suspended just because you slap a piston on a gun. The heat goes somewhere. Its just whether you want to heat up the gas tube or the piston block.

your assessment of heat is correct. i apologize for the generalization and crawfish. the BCG runs ALOT cooler.

[Quentin]

Originally Posted by USEBOTHHANDS

... the BCG runs ALOT cooler.

Which doesn't matter a lot. The BCG can stand a little hot gas, it's not like it is gonna melt!

The main area where the piston can shine is in SBRs or suppressed ARs. For 14.5" and longer you just can't beat good ol' DI.

I would put that $650 into a better upper.

[xdm11chad]

Thank you guys! The tables are now turned. My main use is shooting with all my buddies and will b target and small animals

[fsted2a]

Originally Posted by Quentin

Which doesn't matter a lot. The BCG can stand a little hot gas, it's not like it is gonna melt!

The main area where the piston can shine is in SBRs or suppressed ARs. For 14.5" and longer you just can't beat good ol' DI.

I would put that $650 into a better upper.

Yeah, the longer the barrel, the less advantage the piston has. Quentin and I each have a piston gun, and although they run nice, unless the prices come down significantly, I can't see building another with a piston. Better to invest the money in higher quality parts. "Nuff said.