I'm a lefty. Therefore, I originally wanted a dedicated left hand AR so the brass isn't flying in front of my face or the expelled gasses aren't burning my eyes when I'm rapid firing. This was an ideal build until I started shooting with a suppressor. A suppressor traps a lot of gas and ends up backing up into the upper receiver. Although a lot of it was escaping out of the ejection port, some of it was blowing back and shooting out behind the charging handle. PRI makes a special charging handle that routes the gas to the right but, being a lefty, this would not help me. The only solution was to switch all of my ARs to a piston system. A piston system blows the extra gas out the front of the gas block, and very little reached the upper receiver. The problem with this is that there is no one making a left hand piston upgrade. Stag Arms builds a left hand piston rifle, but I would have to buy the entire upper. The economic solution would be to revert my left hand upper back to a right hand upper, then install a piston system. Here's the build.

Shown here is the original left hand configuration. The lower is a standard AR lower (right hand).





Once I put the upper into the AR block, the first thing to do is to remove the flash hider. The front sight gas block is held in place by two set screws instead of pins, like in Project #1. This made it much easier to remove. This part, along with the gas tube, will not be used in a future build so it will go into storage for now.





Just like in Project 1, the barrel is held onto the upper receiver via a barrel nut. Since I have a freefloat forend, the barrel nut is a bit different. It's made up of 2 parts. There is a barrel nut that holds the barrel onto the receiver. Also, a small jam-ring is installed and is screwed all the way to the back of the barrel nut. The free float forend is installed after that. Once the rail is screwed in as far back as it goes, the top rail is aligned with the rail of the upper receiver. Once aligned, the jam-ring is tightened against the railed forend and it prevents it from moving (in theory). So, the first step in removal is to back out the jam-ring so I can remove the free float forend.




A flathead screwdriver and hammer makes for a fine tool to to loosen the jam-ring. The free float forend is removed and exposes the barrel nut. The armorer's wrench is equipped with PINS that will align with the barrel nut.





Time for the Adam's Arms piston Retrofit System and a new traditional right-hand upper. I'm not going to explain the install process of the piston modification. Adam's Arms has a nice installation video. You can see it here if you are interested.



After the upper receiver has received the necessary bushing, the barrel is installed just like in Project #1. Instead of a gas tube, we will be inserting the piston drive rod. Instead of the front sight gas block, I will be installing the Adam's Arms piston block.






The biggest concern I had was that once the piston block was installed, will I have room to install the flash hider? This flash hider is a quick connect for the suppressor. It needs to have room for me to adjust the piston airflow from 100% (full power), 50% (suppressed), 0% (single shot). That's the knurled knob on the front of the piston gas block. Plus, it needs to actually fit the suppressor on it. I got lucky. Once the flash hider was installed, it sat far enough forward that I could access the adjustment knob on the gas block. The suppressor did not sit farther back than the flash hider so it did not interfere with the knob, either.





The kit came with a modified M4 forend. The forend was relieved on the top cover to allow the piston drive rod to sit below it. Later, I will replace it with a Magpul MOE forend like all my other tactical rifles. This project is complete. The original free float forend will be reused on Project #3.

I have to admit, I didnt follow all that you did, but the pics are awesome and besides who doesnt like looking at pics of guns?

Originally this AR ejected to the left. It had a Stag Arms Left Hand upper. I just swapped upper receivers to make it a traditional right hand eject. I am rewriting it so it makes more sense. Hopefully you can follow the build via the new verbage. If not, let me know how I can make it more understandable.