I started my builder, and I guess I am going to end up spending more money than I wanted to, but hopefully I will have a nice setup.  So far I have:

Les Baer lower receiver
DPMS lower parts kit
Custom-made flat-top upper
JP wood thumbhole stock
Trijicon ACOG sight

I am going to buy a JP 18" barrel with the heat sink attached.  www.jprifles.com

I want a Yankee Hill Machine "Lightweight 4-rail forearm"  http://www.yhm.net/store/forearms.html
What length do I need??
(Keep in mind that this free-floating forearm will cover the gas block.  Thanks guys!!!

From what I could tell, the 18" JP barrels use a rifle length gas system.  A rifle length FF tube will not cover the gas block.  You would need need a midlength gas system in an 18" barrel so that a rifle length tube will cover the block.

Also, the JP block may, or may not fit under the YHM guards.  Keep that in mind.

Yeah, I'm going to put a different, low profile gas block on the barrel.  JP's gas systems costs an extra $200 so I am going with my own.  Hopefully the low-pro block will fit under the handguard.  Thanks!  I'll keep you posted

Quoted: Yeah, I'm going to put a different, low profile gas block on the barrel.  JP's gas systems costs an extra $200 so I am going with my own.  Hopefully the low-pro block will fit under the handguard.  Thanks!  I'll keep you posted

What I am saying - is that with a rifle length FF tube/handguard, and a rifle length gas system, it wont BE UNDER the guards... it will be in front.