But i suck at searching for stuff so if i didn't put the right terms in feel free to link it and tell me this is a repost....

but anyway, why are people saying that for a short barreled upper (I was thinking about a 7.5" noveske) I should go for a piston upper over DI, yet nobody seems to be able to give me a clear reason as to why that is.

I'm not the mine is better type of person, so if there's a good reason hey I wanna konw.

How far is the gas port from the chamber on a 7.5" barrel? Maybe 4" or so? How about on a 16" barrel, 8" or so?
[conjecture]
It stands to reason that when the bullet is only ~4" from the chamber the gas pressure will be higher than when the bullet is ~8" from the chamber. Some quick, certainly flawed, math would suggest that the pressure would be twice as great. The extra pressure slams the bolt carrier group (BCG) back much harder than intended.
[/conjecture]

hrm, Cause i am seriously considering a 10 or an 8 " gun here soon... But i keep hoping Colt will be the ones to sent it out...

LWRC is looking good though.