Saw smiles post and started hummin' the anthem
"I mean, venting dirty combustion gas into the chamber and upper receiver? Whose genius fuckin' idea was that?!'- Churba
Eugne Stoner! Yeah, I know, you probably knew that already. Don't get me wrong, I too think it's a stupid idea to be blowing crap back into the action. And I hate the gas leaking back through the charging handle area into my face too. But the design works as long as you're not using really dirty powder, like the bureaucrats forced them to do back in the day. And technically it's slightly more accurate than a piston. But you know what? Piston guns are running at accuracy levels barely below that of the dang gas block models, So I agree with you, I'd rather have a piston. They run cooler than the gas version too. I just don't think it's as bad as some people make it out to be. But unless you've got me trying to build a precision match model for 1,000 yard shots, I see no reason NOT to have it be a piston gun.
Yes and no - it's Half an MoA at 200 yards. This is not a sniper rifle, you're not going to see big differences till you're well beyond the useful range of the rifle, so it's pretty pointless unless you're building a 1,000+ yard rifle out of one, at which point the question is twofold - can you overcome this with other modifications, and why are you even doing this that doesn't even make sense.
Not using dirty powder, yeah, that's true-ish. It's not going to jam or malfunction as much, but there are two problems with that - First, if you're thinking of it as a combat rifle, then you should be able to pour mud in it, then piss down the bore to clean it, and still have it work first time every time. You might not be able to pick and choose the highest quality ammo, and you don't want to risk malfunction if you can't. If you are - like most - using it for a target or hunting rifle, then that in combination with the weird internal design makes it an enormous pain the arse to clean properly, and you will see more malfunctions over time. Seriously, you bloody near need specialized tools, like jeweler's tools and dental picks to get it properly clean, and even then, it's super irritating.
Now, if I was going to build you a 1,000+ yard rifle, I wouldn't even be going AR platform, or any semi-auto, I'd be going with a nice bolt-action. Simplicity itself.