Some great info here. I would disagree with the bolded part though. There are actually some things wrong with a piston AR, especially in otherwise standard carbine configuration. Bolt lug stress and BCG tilt being the two biggest problems.First, thank you for your service! Second, lube more and clean less. Seriously.
From talking to a buddy that used to be in the Corps and then went on to run the armorer and training programs for Dep. of State far more wear, tear and damage is done by institutionally ingrained cleaning than is typically even done by firing.
Piston systems really shine in three specific areas:
1. Lots of full auto. (Probably not an issue for you but if it is then I want to be your friend. )
2. Reliable operation of a VSBR (Very Short Barrel Rifle, basically barrels under 11.5") in all climates and altitudes with a variety of ammunition.
3. Reliable operation of a VSBR in all climates and altitudes with a variety of ammunition that is suppressed.
Outside of these areas it's just more weight towards the front of the gun making things heavier. It's also that many more proprietary/non-standard parts that may or may not be available.
Is there anything 'wrong' with a piston gun? Absolutely not! If it's reliable and strikes your fancy then rock on with your bad self!
I run a MK18-type weapon from Daniel Defense that is occasionally suppressed. I understand the limitations of this system and it's useful lifespan as well as how to take care of it. If money were no object or they were MUCH more available (and factory supported with parts!!!) I would really like to have a 10.3" HK416... but that likely won't be happening any time soon if ever!
LWRC would be my next choice as it is a well designed system instead of a bunch of drop in parts. They're a known quantity and from what I've seen they go out of their way to support their customers.
At the end of the day though THIS is my preferred piston.
Ek