this + 1

ive seen setups that make no sense on how they get the range/acuracy that they do.

like my 6" inner barrel (152mm) M4 shooting roughly 315fps can reach out and touch people easily beyond 200ft.

I really really wish there were verifiable consistent lab quality tests of all these setups. The contradictory information makes choosing what internals to get impossible. For what ever reason my groupings came down an average of 2 inches at 150 feet, and I felt (but did not test) my effective range improve.

the prep and setup are usually more the defining factors then the parts used... I don't care how much you've spend on parts or what brand they are.. or what thousand your gun cost... if it ain't consistant, if the hop up chamber is moving around.. if the barrel is moving..etc etc... all the money/brands chest beating ain't gonna do shit.

Its very simple
This isn't real steel, longer barrels don't equal more accuracy
A 6.01 barrel will theoretically have the same accuracy as a 6.10 barrel, but the 6.01 will foul faster causing accuracy loss after just one mag.

With my VSR's 6.03 barrel I noticed accuracy loss due to fouling after just 120rnds

The BB isn't actually supposed to touch the barrel at any point after the hop, its just a cushion of air that guides it centered down the barrel. So whether its a 6.01 or 6.10, the physics are the same, they both use air pressure to center the BB, just one has more room to allow for fouling.

The same goes for shorter barrels, beyond a certain length, once a BB is stabilized its stabilized and no extra amount of barrel will make it any more stable.
Case and point; compare a stock M16a3 against a KSC USP
The USP gets very comparable range despite having a 4" barrel vs the M16s 20" barrel.

Too many variables at play.
Platform variations, installation skill, tuning time, consistency, manufacturer tolerances, I could go on.

All else being equal, the best possible AEG barrel group setup has been accepted to be an ER-hopped/EM-nubbed 455mm 6.03 stainless barrel with the barrel consistency as high as possible and a good-sealing rubber. I've tested this theory personally by swapping an identically set up 363mm and 455mm barrel group, keeping the same lower receiver the same. Ignoring barrel volume for a second, the grouping size and range was noticeably better with a 455mm barrel. I do recognize that not everybody wants to run a 16" barrel AR-variant or a full-length AK, etc. so the 363mm is a good tradeoff. I have another barrel group at 230mm that I'm going to try when I get back.

Flat-hops are nice but it's just an evolutionary step towards the R-hop. I'll say this again: a proper R-hop install should not take more than 10 minutes more than a Flat-hop setup (excluding dry time).