How come no one ever talks about the diminishing accuracy you get with the added heat in the AR system? Besides the reliability, systems that do not throw a ton of heat back into the receiver can stay more accurate for a longer period of time...at least that's what I hear...
::cue story time flashback music::
I didn't know this happened until hearing a range story from a vet who used to be a sniper back in the day (I know this is how all range stories start, but this one is actually 2nd hand as opposed to hearing from a friend of a friend of a brother who read it online). He said that his main beef with the AR platform is how it dumps where it eats. No news there. I was surprised how he went on to talk about how this hurts the weapon's performance, in addition to durability. He said he when he was out shooting at 300 yards, he made a nice 2" group to start off the day. Feeling good, he continued to shoot, but was getting discouraged at how his groups had widened to about 6" as he kept shooting, with nothing he was doing working to close it up. Seeing he was at wits end, someone else at the range told him to let the gun cool off for 30 minutes or so, then try again. He did this, and sure enough, got the 2" group back. At first he thought it was just from taking a break from that rifle, so he loaded up a mag and let the guy next to him let it rip, before getting the now hot rifle passed back to him. He sighted up, took his 5 shots same as before, and sure enough, was back at 6". The stranger then explained what was going on, and I don't remember the nitty gritty details from part because I don't own an AR and am not familiar with the parts, but I'm reasonably sure it was something about how the heat screws with the springs in such a way that is detrimental to the performance of the weapon...or something. After that day, he became a believer in a piston system, because even though they may be inherently slightly less accurate, they stay cooler much longer, which means you won't see your groups widen as quickly.
Now then, this is purely anecdotal, and I was wondering if anyone could back it up or debunk it? I'm as curious as the next person, and don't like believing that which is not true, so if this is impossible, yell it out now before it gets out of hand. If, however, this is true or could be true...I suppose no one cares because how many people are going to take that many precision 300 yard shots with an AR15 these days?