I'm sure y'all get sick of all the noobs, but just gotta couple of questions that I would like your advice on.

I'd ask these questions in the other forums, but too many seem bent on Colt bashin.

I've got a '01/'02 Colt Match Target Competition HBar II (i guess that's pretty close to model 6721 w/o all the post-ban accessories?) -- flattop w/ 16" bbl w/o flash supressor.

I just got a collapsible stock that my cousin got for me when he got back from Iraq, and I'm trying to set up an optics system for it now.

If I'm gonna do it, I wanna do it right, so I've been looking at the Trijicon ACOG RCO M4 and the TA31F.  I'm gonna remove the carry handle, and just have it on the flattop w/ some BUIS (I'll worry about those later tho), and have lots of XM193 ammunition.  I'd rather stick w/ 55 gr. and from what I understand, although the RCO is set up for 16" bbls, it's set up for 62 gr. and if I'm gonna pay that much for a scope I'd really like the BDC to be right on.  

Any of ya'll have 16" flattops and ACOGs and have a preference for any of the different models?

And secondly, I'm going to go to a local gunsmith and get the bbl threaded for a flash supressor, and wondered whether that would effect the ACOG predictive accuracy -- does that extra half inch/inch effect the ballistic coefficient??

Thanks for your help.
 

good to see you chime in, lbb28

The ACOGs are designed for certain barrel lengths, and calibers, as well as configurations

The ideal models (to the best of my limited knowledge) for the 16 flat-top are:

the TA 31F and TA31-RCO

The TA31 can also be used, but is intended for the carry handle. (the one on my flat-top)

A very good source for information on this very topic, is Mike @ CSGunworks

He is very accessible, expert on these things, and is listed in the Industry Section and Equipment Exchange forums here.

Of course you could always contact Trijicon - as I did originally, and they are very informative and helpful.

Great choice for an optic to take that Colt up a serious notch

Mine (this one a Bushmaster lower w/LMT upper and Troy BUIS)



and a Colt with the TA31 (donut reticle) and ARMS 40L BUIS

just re-read your post and will offer a suggestion on the barrel modifications

Many here have done the same work, and a very popular option has been to re-tool the 16" HBAR to a 14.7" with a permanently attached A2 or birdcage FH

Others have gone 14.5" and permanently attached the Phantom or Vortex FHs and realize improved reduction in barrel flash.

with either, you will not be sacrificing measurably in the accuracy column, as long as the work is professionally done.

Check out the ammo-oracle. It is a resource with all the ballistic data on various bbl. lengths, ammo choices and such

HTH

for gunsmith options....check out ADCO in the industry forums for discussions and insight into barrel mods.

I prefer the TA11 series for better eye relief. Tradeoff is increased weight and bulk.

I had a TA31 with an LaRue mount on my 6721. Its very nice BUT if you shoot consistantly under 100 yards you may find the 4 power a minor problem transitioning targets.  
I know the both eye open principal is supposed to overcome this but Im over 40 and my eyesight is less than perfect nowdays even with contacts.
For 3 gun stuff it slowed me down a bunch at targets 50-75 yards. Once you get into 100 yards or so it is top of the heap in my book. Just my opinion and I loved the one I had but if you shoot over half under 100 yards I like my Aimpoint on a LaRue mount.
If I were a young buck with perfect vision I may feel different.