Hey,  

 I tried to beat the sickness and sold all 4 of my AR's.  Well the bug is back so might as well not fight it.  I have had everything from 11.5-26" barrels but not a mid gun yet.  I seen a pic of a 18" midlength barrel somewhere can someone point me?  I think I like building these things more than selling cause I swapped over and built a really sweeet Rem 700 thats a tac driver but is boring.  and it weighs 20#'s.   Anyway some fingers pointing the right direction would be cool.

I have...
Bushy  stripped upper/lower.

need to know where to get
Barrel,   18"  midlength   1x7 twist    preff stainless

Might get,  
Armalite or JP float tube.(the new JP tube looks like good shit)
Prolly JP low mass operating system (had one in a prev custom that was a 1/4 MOA gun)
JP Trigger since I have had awsome luck with em,  but would like reco's on jewell.
I do alot of bench shooting so prolly go with the JP Lam stock on this one also. (makes an AR the most comfortable gun to shoot in the world)

The only 18" middy's I can think of are usually "SPR" style barrels. Make sure you ask before you buy if you really want a mid-length gas system because some are rifle length. Here's one from WOA (sold by ADCO) but I can't say for sure if it's a mid or rifle length gas system...

ADCO - WOA SPRr Barrel - its on the bottom of the page.

Good luck

are those 1:7 or 1:8?  I think true SPR barrels are something like 1:8.8 and are rifle length.

I've got a 16" midlength from ADCO.  It's NOT one of the giffman type barrels.  Steve had a few barrels made to HIS specs and he turned them down to 0.900" under the handguard area and fluted my particular barrel.  It's a 1:7 SS with a match chamber that shoots 5.56 really well (XM193).  It's got the magical M4 feedramps, and milled flats for a FSB.

Compass lake will build you a nice 18 mid length gas tube, even make a lefty for ya.

Quoted: are those 1:7 or 1:8?  I think true SPR barrels are something like 1:8.8 and are rifle length.

True SPR barrels were 1/7 and are rifle length gas systems.

Link to some SPR info