Well, no matter how "properly tuned" mine are powder residue still seems to find its way in there. Almost like it's just part of the way a DI system is supposed to function. Go figure.
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Yes, they are going to get a bit more fouling than a piston. I found a little faster powder to make sure that the powder is all burned before it gets to the gas port helps a good deal. Use slow powder like Varget, it will be a mess.
X-Terminator and AA1680.
If the AR was supposed to have a piston, Stoner would have designed it as such. He did design a piston rifle the AR 18 which actually is a great little rifle.
To me, the piston is a hardware fix for a software problem. The biggest selling point is a cleaner bolt/carrier.
Face it, how many really enjoy cleaning a nasty bolt and carrier?
IMO a piston adds components that can fail/malfunction, mechanical complexity, weight forward on a barrel and cost.
Parts left off cost nothing, parts left off cannot fail.
Using the few powders and bullet combinations I have used as a comparison, I'd say the issue was very small. Powders have more effect then operating system.
I see what you did there.....