*This upper receiver assembly has a barrel that is shorter than 16". This upper is only for use on AR pistol lower receivers and NFA registered Short-Barreled Rifle (SBR) lower receivers. All NFA laws apply!
The debate between the Direct Impingement or Gas Piston system, and which is better is an old one. It's a personal decision. However, until you've experienced both, you really don't know. While you might not find a GP gun for sale at the retail level, you can build one. Grab yourself a PWS PRO upper, pin it onto your old AR-15 lower, and decide for yourself.
You could buy all the pieces, and build out a good weapon. The design of an AR-15 makes this easy. On the other hand, why not scroll back up, get a complete PWS upper, and save yourself the hassle. When you look at the PWS PRO upper and see what they put inside, you won't be disappointed. From the free-floating M-LOK Handguard to the Radian Raptor Ambidextrous charging handle, you will find parts that you would have chosen yourself.
PWS keeps its focus on the actual operator, and how their weapon will perform in the real world. The long-stroke Gas Piston system that PWS employs is quite similar to the battle-tested AK-47. The purpose and goal of a PWS upper is function and reliability. When they first came on the scene, a Gas Piston driven AR was pretty expensive. However, prices have steadily come down as the market opened. Today, you can get a high-quality PWS PRO upper for less than many lesser grade receivers used to cost. So, if you want to try a Gas Piston gun, you might as well give it a fair shot. Pick up a PWS upper today and decide for yourself.