Adams arms makes one for a dpms gen 2 variety. But it is $600, you can only use their rails, and god only knows how well it will perform/last.
There is probably a reason you don’t find a lot of 308ars with pistons and can only find one company making kits. Remember there is a lot more pressure running through these than ar15s. And you are probably not firing as many rounds as you would with an ar15 so the amount of carbon shouldn’t be that bad. Besides you would be surprised at the amount of carbon these guns can handle and still run. I get it would be easier to clean, but that’s why I like my nickel boron bcgs
this is where @98Z5V comes in and says, “don’t complicate sh1t with complicated sh1t.”
It’s your rifle, so if you are set on a piston system, go for it. Just will create extra cost and might create extra problems. Either way, good luck and we will be here to help.