Does anyone have a preferred brand or manufacturer of a Gas Piston that they've used in the past? I think I'm going to install one on my AR and the one I'm going to build.
If you want a piston system that you can install yourself, the ARES kit is the only one available right now.
If I were to buy a piston AR upper, it would be the LWRC.
However, I sugggest you DO NOT waste your money and effort on a piston system for the AR, but instead, save your pennies and cross your fingers for the Bushmaster ACR/Masada to hit the market.
I used my standard Rock River carbine for 2 days of a 3 day Pat Rogers carbine course, and for the 3rd day used a ZM Weapons LR300, which may or may not be a piston, but is sure isn't direct impingement.
I couldn't tell any difference (except for that freaking Mini Y comp that was on the ZM at the time - now replaced by a Phantom FH, but I digress) in performance between the two carbines.
I was able to fold the stock on the ZM, making for a fairly compact package.
IMO, if you shoot 1000's of rounds a month, maybe a piston is the right move.
If you shoot 1000 rounds in a years time, stick with DI, and spend the $$ on ammo and mags - we're gonna be needing both shortly.....
The above are my opinions, and worth about what you paid for them.