Funny you should mention that: I called Colt yesterday to ask about the pin size, and they told me my 6920 was manufactured in December of 2008 and it has the .170 pins.
Great looking rifle Jmorrell. If you don’t mind me asking where did you get it and how much did it run you?
Check your private messages.
I just picked one up as well (6920). Trying to decide what to do to it first. It doesn’t seem worth to change the stock because I had it pinned (for NJ) I would like to put on a quad rail. Anyone have any suggestions?
I’ve added a Daniel Defense Omega 7.0 free float rail system; a Surefire G2 LED light on a LaRue offset light mount; and the Grip Pod from an earlier AR build. Also included is a Tango Down PR4 sling attach point. I removed the GG&G BUIS so I can move the ACG back get a better sight picture. The Grip Pod will be replaced a LaRue FUG as soon as it arrives (hopefully next week).
Can you put on an oversized hand guard like 9 inches or does that require other significant modification?
I have no experience with the longer hand guards: maybe someone else can help you.
The other question is how does one install a free float hand guard with a muzzle bake permanently attached? Aside from having a smith drill the pinned brake i dont know how one could do it.
I was talking to my Gunsmith today, he said something about soldering or pinning.
The DD Omega is a two piece free float handguard, so you don’t have to remove anything to install it. It goes on in less than five minutes and the only tools required are a flat blade screwdriver and an Allen wrench (the Allen wrench is included with the Omega).
you have made the best decision of your life…, a Colt 6920 will never lose it’s value 
looks just like mine except for the stock.