My build.....AR build anyways.
Who's lower parts kit did you get?
You say carbine, are you going 16" or 14.5"? Gas system length? Anything over 12" should be a mid-length gas system unless you like .22's that recoil like .30's ;)
What kind of upper, fore-end, stock and grip setup are you going with?
I'm partial to bravocompanyusa.com for parts supply, but I'm biased.