New LE6920, and new to this forum.

http://www.coltsmfg.com/Catalog/ColtRifles/ColtCarbinesI.aspx

First question, does this have the standard M4 profile barrel, or is it the heavier M4A1 profile?

Second, I have fired around 200 rounds of 55 gr through it, and it has functioned flawlessly (even with some old GI magazines, that are troublesome in other AR's!).  I will be switching to Black Hills 77 gr (equivalent of MK262 Mod 1), so is it wise to install something like this?  

http://www.bhigear.com/bhienhancedm4sopmodboltupgradekit.aspx

Third, I have an Trijicon ACOG TA01 (NOT a TA01NSN).  It is calibrated for 55 gr from a 20" barrel, mounted way high up on the handle of something like an M16A2.  I am thinking of getting the TA51 flattop adapter, and trying it on the M4.  Would it just be a waste of money, time, and ammunition to try this out?  I am concerned that the trajectories will be so very different, that it won't even be close enough to be workable.

Thanks!

The barrel on the 6920 is a standard M4 profile with 203 cut out.
I highly recommend PMags over USGI. I sold off all my USGI mags a long time ago. You have a good rifle. I would add a good sling and light. Try the ACOG and see how close the BDC is. I use the TA31RCO M4 on my Colt 6700 and it is very, very close with my 55 gr FMJ reloads. On my M4 I have installed the M4 SD II flash comp and it is amazing at what this does to control muzzle rise!!!

You don't need to upgrade your rifle if you want to shoot the heavier stuff

No problem on mounting the ACOG on the flattop you should be close enough that you won't be able to tell a difference.

Really don't need the bolt kit upgrade and you have the standard profile not the heavier profile.