I had decided on the 6920, then I read about the 6721. The only difference I can see is the barrel (HBAR and 1/9) ?? It is a better price, if the barrel is the only difference I might get a 6721 … need advice please.
Thanks for putting up with a newb,
Bigdog
6920 = M4 handguards, M4 profile bbl w/1x7 twist.
6721 = CAR handguards, HBAR profile bbl w/1x9 twist.
The 6920 weighs 5.65 lbs. and the 6721 weighs 7 lbs even. The difference in the twist rate makes no practical difference with the weight ranges of commonly available ammunition in the opinion of most. I chose the 6920 because it was lighter than the 6721 and I judged the 1/7 twist to offer the most versatility.
Thanks for the replies.
For a $200 savings looks like the 6721 has moved into first place.
Check it out: https://www.policeguns.com/catalog/index.php?cPath=16_236&osCsid=2f322a665ba76b2848d5bd0c356cf0b3
That’s a much bigger price differential than I usually see, and even though I favor the 6920, that might swing the deal for me. How much was the 6920 you were looking at?
I’m sure you’d be happy with either, but here’s my thought process;
If I’m willing to spend over 1 thousand dollars on a gun, $200 is pocket change compared to getting what I really want. I like the lighter weight of the 6920, but even if it was something as simple as the bad a$$ looks of the 6920 barrel 
, that’d be enough for me to pay and extra $200. Because in the end, you’ll probably keep the rifle for a LONG time (in my case I plan on passing it down through my kids:D ). The $200 dollars you saved will be forgotten by the time you get your next paycheck.
I’m a walking inconsistency, I suppose, because I’ve got a 7 pound M4A1-profile LE6920HB. 
There are a number of different ways of looking at the weight issue, and usually – almost always – less is more. Still, there are cases where a bit of weight isn’t unwelcome, and my early SP1 Colt carbines always struck me as a bit “whippy” at the muzzle back in the 80s. To some degree, you need to consider how much you wish to modify the weapon: a 6721 with a ShortDot or CompM4 strikes me as a near-perfect rig, but if you’re going to hang lights, lasers, night optics, VFGs, magnifiers, trailer hitches and who-knows-what-else on it, then weight will quickly become a relevant concern.
For hunting here in Germany, I favor a reworked G.33/40 (small ring 98) mountain troops/fallschirmjaeger carbine in 8mm Mauser that weighs next to nothing, yet fires a very heavy recoiling round – but I’m only firing it two or three times in an outing. I can handle the momentary pain for the convenience of something that is extremely easy to carry all day long. Well, actually I take some perverse pleasure in the swift kick when it comes time to pull the trigger, but that’s just a side issue. LOL
For defensive/carbine work, the recoil of the 5.56mm isn’t really an issue, but the heft and handling certainly are. Both the 6920 and the 6721 are excellent choices, and in a perfect world, a guy would probably own one of each. Which is best-suited to your needs is a question that only you can answer, but for a lightly-modified carbine with excellent stability and target tracking characteristics, I would seriously give the 6721 a long, hard look. It remains perhaps the most underappreciated variant in Colt’s entire lineup, and the longer I’m around the A3 Tactical Carbine, the more I like it.
The price surely isn’t hard to take, either. I’d call the 6721 the little-known “sweet spot” at the top of the AR market; doubly so, when you consider that 99.9% of the 6920’s we all pay a premium for will never have an M203 mounted to that ridiculously all-consuming (for purely cosmetic reasons) stepped barrel notch.
Chief
Great replies from everyone, thank you all!
I do not plan on adding lasers, lights, launchers etc etc … the only thing I will mess with is optics … the extra 1.4lbs is nothing to me. The prices I see right now are $1300 for 6920 and $1100 for 6721 … and my local dealer lists the dealer cost of the 6721 as higher than the 6920 (not sure why). My main concern is quality and reliability, which the 6721 will provide as well as the 6920. I would never buy a weapon based on its ‘looks’ as someone suggested … so paying $200 extra because the barrel looks better is not in the cards for me. It will be 2-3 weeks before I am ready to order, if I can still find the 6721 for $1100 at that time it will be my choice.
Bigdog
Thanks LT, this lowers the price differential to $129 vs. the best 6721 price I’ve found … I’ll still go for the 6721 at $1100 if I can find it when I’m ready to buy, otherwise I guess this deal on the 6720 would be best. Wish I could pull the trigger now on the $1100 deal, but the wife is making me stick to a firearms budget and she is holding me to the exact day my budget funds become available, which is in 3 weeks 
Bigdog
I just looked at Clyde Armory and the price difference between the two is $10. I thought I wasn’t seeing straight, so reloaded the page, triple checked the numbers. They stayed $1219 for the 6721 and $1229 for the 6920.
The HBAR barrel serves no purpose on a fighting gun and I will not contribute to this craziness by purchasing one.
I guess that comes down to personal opinion. I like the HBAR
I was tempted, but after reading and talking I think I will go with the 6920.
It’s a good choice if you’re going to run a suppressor. Less bbl flex = less vertical shift in POI. Despite what others believe it’s also not the end of the world if you get one. It can always be reprofiled if you really come to hate the weight. You could have it reprofiled and cut to 14.7" and have the A2 comp perm. attached for about $100 or less.
I agree. I have both a 6920 and a Colt MT M4 and intend to make a 6721 my next purchase. While maybe not perfectly practical by today’s standard profile, I like it for several reasons.
I’ve owned them both and I will stick with the 6920, although the 6721 is a good gun as well
Hold a hallway with a 6721 with light mounted for about 30 minutes. Trust me, you’ll want a 6920.
I have been torn between these two models as well as the Noveske N4 Light )Basic) for my non-NFA rifle. Seems like one week I make a decision then a thread will come up the next week and I am torn again. Have almost narrowed it down between the N4 Basic or getting a 6721 and having the Noveske N4 barrel added on it to get the simple look, M4 (lower than HBAR) weight and 1/7 twist; the best of both worlds.
That raises a wholly relevant point: we need to be realistic with respect to our expectations for how we intend to employ the carbine. If it is to be primarily a shooting iron that will spend most of its time slinging lead at the range, then that plays nicely to the 6721s strengths. If it is to be primarily a duty tool that will spend most of its time being carried from one interdiction to the next, that tips the scales in favor of the 6920 – or better yet, to the even lighter 6520 (AR-15A2 Government Carbine). Odd that we hear so little about the latter, no?
While I sincerely respect and acknowledge Pat’s position on the 6721 (and Scott Ryan’s as well), I dare say that he is addressing a relatively small demographic here. The overwhelming majority of our membership has no pressing need to employ the carbine as a fighting gun, as a patrol arm, or as anything of the sort. Outside of the occasional training/school stint, most of these weapons are destined to live out their lives as range tools and objects of interest with a backup role in home defense. I’m not sure how you communicate that effectively to the guy who is set on buying a 6920 solely because of the way the barrel step looks, but I’d much rather share a shooting position with a guy that was honest and realistic about his needs, and chose accordingly.
As an aside, I find it an interesting footnote on weapons development that we have arrived at a point where a 7 pound long arm is now considered a heavyweight. Our grandfathers and great-grandfathers would no doubt be enjoying a good laugh at our expense over this.
Chief