FYI, WASP is not propietary - it's a form of Melonite (I don't know if it's Melonite Q, Melonite QP, or Melonite QPQ). Melonite is ferritc carbonnitriding, nothing new, but an EXCELLENT heat treatment.
I prefer to stick to DI on the ar platform. There's no hardened steel rails guiding the bolt carrier back. With a piston, the force that sends the carrier back does not originate from the centerline of the bore, but above it, which tilts the carrier into the reciever and/or buffer tube.
CMMG runs a larger dia 'tail' of the carrier if my memory serves me right, which is designed to minimize this - once you get the usual amount from break in that should be it.
The force on the carrier that moves it comes from the centerline of the bore on the DI systems, which aids in it's repeatability, and accuracy. I have a chrome lined bore/chamber and a TiN coated bolt carrer group that I've ran bone dry, 4 mags as fast as I can, without a problem, and then repeated the same test by taking teh bolt carrier group and literally soaking it in oil - no problems that way either. I have yet to run into issues with my new phosphated, chrome lined, bolt carrier group either.
In the AR platform, to me, it's simply an answer to the "but I want a piston!" demand. They can and will get just as dirty as a DI gun (although it will take more rounds, unless suppressed), and can and will malfunction, probably to the same degree as a maintained DI gun. They do suffer from a little less accuracy, but unless you're a precision long distance shooter, it shouldn't matter to you.
In short - if you want a piston gun, I'd reccomend shopping around for one where the base platform was designed to be a piston operated action. I'm holding out for the Remington ACR, whenever that comes out, for my piston gun
