View Full Version : 6920 have any advantage over 6720
Setting BUIS aside, it seems to me that the only difference between the Colt 6920 and Colt 6720 are the barrel profiles. The 6920 has an M4 barrel with M203 cut but the 6720 has a pencil barrel. Further, if the 6720 is going to experience barrel due to heat, I think the 6920 would experience the same warpage at the location of the M203 cut (?).
So I do not see any advantage to the Colt 6920 over the 6720.
What am I missing here?
http://colt.com/law/images/lecarbine.jpg
http://www.everydaynodaysoff.com/wp-content/uploads/2010/03/colt-6720.jpg
Don't know if this helps, but some discussion here:
https://www.m4carbine.net/showthread.php?t=47357
:cool:
Heavy Metal
12-25-10, 19:55
They are both light under the handguards close to the chamber where the bulk of the heat is generated. .gov profile is bass-ackwards to the way a true heavy barrel should be.
.gov profile barrels make zero sense.
Get the full lightweight profile rifle.
In one thread, possibly the one referenced, it was stated that the 6720 front sight base was not 'F' marked. The 6920 fsb's are 'F' marked.
I've not looked at a 6720 so can't comment further.
If I had a flattop upper it seems that the 'F' marked fsb would be preferable, unless the fsb actually was 'F' height and just not marked.
Personally, I would prefer the skinny or lightweight barrel (also referred to in some circles, I've been told, as the 'standard' barrel) of the 6720 as mentioned above.
I can't think of any reason to get the heavier rifle.
RogerinTPA
12-25-10, 21:37
The 6720 has one less piece (removable handle) to throw away when you mount a RDS and it's lighter.
6720 differences:
• Lightweight profile barrel the entire length
• No carry handle; instead includes Matech BUIS
• No front side sling swivel mount
• Lower stamped "Colt AR-15A4 Lightweight LE Carbine"
• Come with (2) 20rd PMAGs
Failure2Stop
12-26-10, 00:55
Here's the deal:
It's a 6920 with a lightweight barrel, with all the implications of testing, specs, and quality that a 6920 brings.
It's what users have been asking for for years.
If this had come out in 1998, it might have changed the face of carbine concepts as we know them. However, since the introduction and widespread implementation of mid-length gas systems, it is pretty much just an "also ran" now.
The 6940 and 6720 are sad proof that Colt needs to get more forward thinkers on their payroll.
6720 differences:
• Lightweight profile barrel the entire length
• No carry handle; instead includes Matech BUIS
• No front side sling swivel mount
• Lower stamped "Colt AR-15A4 Lightweight LE Carbine"
• Come with (2) 20rd PMAGs
Short and to the point!. Thanks
Beat Trash
12-26-10, 13:45
I've owned a Colt 6520 since 1994.
A few years ago, I bought a Colt 6920 for each member of a family of 4. If the 6720 were available when I was buying my 6920's, I wouldn't own a single 6920.
It's not worth it to me to sell off the 6920's and replace them with 6720's. But if starting over again, I'd go with the light weight barrel.
I have 2 6920 one thats has all the goodies free float rails ect. and the other thats bone stock to keep its light and simple. I will be picking up a 6720 from a friend to replace the light and simple carbine. Now what to do with the stock 6920 ?
http://i109.photobucket.com/albums/n56/aimeehoge/colt6920.jpg
Got to love the Colts
http://i109.photobucket.com/albums/n56/aimeehoge/ARs.jpg
6920's last two on the right
It's not worth it to me to sell off the 6920's and replace them with 6720's. But if starting over again, I'd go with the light weight barrel.
That's the approach I've taken as well. For my purposes, the 6920 offers nothing over the 6720, while the 6720 is a bit more user friendly on longer outings, and with a greater number of shooters.
Here's the deal:
It's a 6920 with a lightweight barrel,
Being a “picker of nits” I’m going to add this. The 6720 is more appropriately described as a 6520, with a flat-top upper receiver. The 6720 uses the exact same barrel assembly found on the 6520. This is why the 6720 does not have an “F marked” front sight base (which is not the big deal that the Internet Commandos are trying to make it out to be.) This is also why the 6720 has a standard sling swivel and not a side sling swivel.
6520/6720 barrel assembly
http://www.box.net/shared/static/51fa84s0bi.jpg
I’ve been doing 6520 conversions to flat top upper receivers for many years. It’s one of my favorite configurations. The heavier barrel of the 6920 does however produce slightly better accuracy than the light-weight 6520/6720 barrel.
http://www.box.net/shared/static/z63cvxm04g.jpg
http://www.box.net/shared/static/zh54zitue3.jpg
6520 conversions
http://www.box.net/shared/static/f5na08p947.jpg
http://www.box.net/shared/static/ebxqa8pzdf.jpg
http://www.box.net/shared/static/xsi579xo9v.jpg
http://i672.photobucket.com/albums/vv81/gocartmozart2/snapshacklefullcabine01.jpg
http://www.box.net/shared/static/lrz0u0gf52.jpg
http://www.box.net/shared/static/08zo1sz3bu.jpg
....
Molon, is there any particular brand of flattop upper that you prefer for your 6520 conversion to flattop?
Molon, you deserve to win an Oscar for gun forum posts!
Molon, you deserve to win an Oscar for gun forum posts!
No kidding! I have yet to come across a Molon post that I didn't learn something from.
500grains
I'm so used to your old avatar that the new one is buggin me out. :sarcastic:
Wait, Molon, your group size with the LW barrel was a 60 shot group, and the group size with the govt barrel was a 30 shot group. I would expect the group size to open up a bit, when doubling the round count, for the LW barrel!? I would like to see those two barrels tested again, this time, with the same number of rounds fired. Thanks for the post, though.
Failure2Stop
12-27-10, 04:24
Being a “picker of nits” I’m going to add this. The 6720 is more appropriately described as a 6520, with a flat-top upper receiver. The 6720 uses the exact same barrel assembly found on the 6520. This is why the 6720 does not have an “F marked” front sight base (which is not the big deal that the Internet Commandos are trying to make it out to be.) This is also why the 6720 has a standard sling swivel and not a side sling swivel.
Ha! You are, of course, absolutely correct.
I consider my nit thoroughly picked.
I should have described it as "essentially" a 6920, per my intent.
Thanks for maintaining the integrity of information.
Submariner
12-27-10, 09:59
If this had come out in 1998, it might have changed the face of carbine concepts as we know them. However, since the introduction and widespread implementation of mid-length gas systems, it is pretty much just an "also ran" now.
If we had had a crystal ball in '98, we would have bought gold at $300 and waited for BCM ML carbines. Who knew? Nevertheless, "also ran" works pretty good.
We began acquiring Colt LW barrels and M4 barrels in 98, during the ban, along with the rest of the Colt upper assembly parts. By June 2003, Wes Grant had assembled for us four complete Colt uppers with the LW barrels except for KAC FR RAS rails (LaRue didn't produce FF rails yet.) At our first EAG COC that summer, Pat pointed to one and said, "Wus dat?"
They still run. Parts made to a standard and assembled by a pro.
Wait, Molon, your group size with the LW barrel was a 60 shot group, and the group size with the govt barrel was a 30 shot group. I would expect the group size to open up a bit, when doubling the round count, for the LW barrel!? I would like to see those two barrels tested again, this time, with the same number of rounds fired. Thanks for the post, though.
http://www.box.net/shared/static/in8cal2pcg.jpg
....
I'm so used to your old avatar that the new one is buggin me out. :sarcastic:
That other one was the avatar that I had before and this one is that avatar I have after. But the hair is not consistent between the two. ;););)
http://www.box.net/shared/static/in8cal2pcg.jpg
....
Interesting....the LW's mean group size increased by .02", when firing 30 less rounds!? Different day, ammo, breeze, luck, I guess. Thanks for your work, Molon. This inspires me to do the same, once it warms a bit. I may take out a 20" govt, 14.5" M4, 14.5" mid LW, 16" mid LW, and a 16" CHF mid LW, and use the same optic, and try different ammo, and see what groups I can come up with.
RogerinTPA
12-28-10, 19:36
Based on your testing, is it accurate to assume that the thicker the barrel profile, the more accurate the barrel is (Individual shooter variables excluded). This is something that I've noticed over the years. In my competition days, a heavier match barrel was more accurate.
Is it fair to assume in stock barrels, the same would be true? Is that a SOCOM profile barrel will be more accurate than a government or LW barrel?
http://www.box.net/shared/static/in8cal2pcg.jpg
....
Based on your testing, is it accurate to assume that the thicker the barrel profile, the more accurate the barrel is (Individual shooter variables excluded). This is something that I've noticed over the years. In my competition days, a heavier match barrel was more accurate.
Is it fair to assume in stock barrels, the same would be true? Is that a SOCOM profile barrel will be more accurate than a government or LW barrel?
That's very interesting. So indeed I was incorrect about accuracy from standard profile barrels not being intrinsically less accurate, at least as demonstrated in carbine length. Although the difference really isn't anything to write home about unless you're shooting benchrest or DCM matches or something. I wonder if rifle length barrels behave the same way? I imagine they would since the skinny part is even longer.
IrishRifles
12-29-10, 12:25
What would you say is a must replacement on the Colt 6920? :confused:
What would you say is a must replacement on the Colt 6920? :confused:
Nothing, why would you assume there is something that must be replaced?
IrishRifles
12-29-10, 13:39
I have read that some stock Colt parts needed to be upgraded with better after market ones, like the trigger for instance.
I have read that some stock Colt parts needed to be upgraded with better after market ones, like the trigger for instance.
The beauty of the 6920 is you do not NEED to replace anything. You may WANT to (everyone does), but do not NEED to.
6920's are solid performers and reliable out of the box.
I have read that some stock Colt parts needed to be upgraded with better after market ones, like the trigger for instance.
According to whom? The stock single stage trigger in a Colt is all you need for a fighting gun.
Failure2Stop
12-29-10, 14:44
If we had had a crystal ball in '98, we would have bought gold at $300 and waited for BCM ML carbines. Who knew? Nevertheless, "also ran" works pretty good.
Damn, what is this, call F2S out day?
I kid, I kid.
Once again, I agree.
My first post was a bit more negative sounding than I meant it to.
I think it's great that Colt is offering these, I just wish they had listened earlier.
I stopped myself from getting one a few times since their release, and only because companies like DD and BCM began offering LW middies.
I still might pick one of these up for a truck gun, but it's getting harder and harder for me to justify redundant rifles.
Damn, what is this, call F2S out day?
I kid, I kid.
Once again, I agree.
My first post was a bit more negative sounding than I meant it to.
I think it's great that Colt is offering these, I just wish they had listened earlier.
I stopped myself from getting one a few times since their release, and only because companies like DD and BCM began offering LW middies.
I still might pick one of these up for a truck gun, but it's getting harder and harder for me to justify redundant rifles.
I have two "fighting" carbines. My 6920 with a Colt m4 barrel + AAC Blackout, and a BCM 16" LW BFH midlength. I just changed uppers last week when the LW BFH was released. I figure the only other serious use rifle I want is a KAC SR-15.
http://www.box.net/shared/static/in8cal2pcg.jpg
....
Thanks for taking the time to post the photos. The difference is interesting to see. For a fighting gun the LW bbl looks like an excellent compromise. The group is almost twice as big but it is still an excellent group.
Too much exposed bbl for my tastes, but I like it's overall apperance.
Based on your testing, is it accurate to assume that the thicker the barrel profile, the more accurate the barrel is (Individual shooter variables excluded).
The most consistently accurate barrels that I have tested have a “bull barrel” profile. I doubt that is coincidence. The 10-shot groups pictured below were all fired from a semi-automatic AR-15 with a Krieger barrel that has a “bull barrel” profile.
http://www.box.net/shared/static/0fuxcv68qk.jpg
http://www.box.net/shared/static/r35j7qm5i1.jpg
http://www.box.net/shared/static/pt7y91nj7y.jpg
http://www.box.net/shared/static/edqv78hn81.jpg
Is that a SOCOM profile barrel will be more accurate than a government or LW barrel?
The Colt M4A1 SOCOM barrel
http://www.box.net/shared/static/dq2orr4r7z.jpg
A genuine Colt M4 SOCOM barrel is 14.5” long and has a medium contour underneath the handguards (not a heavy barrel profile). The barrel has a NATO chamber and a 1:7” twist. The SOCOM barrel has the typical M4 circumferential cut-out located approximately 1.4” forward of the gas block for the attachment of an M203, as well as rectangular shaped cut-outs underneath the handguards on the port and starboard sides of the barrel, located approximately 1.4” aft of the gas block, for the same reason. The SOCOM barrel employs the carbine length gas system.
http://www.box.net/shared/static/sh1g1d1ph2.jpg
http://www.box.net/shared/static/8m6luc1e9j.jpg
The barrel stamp located just aft of the flash suppressor reads:
C MP
5.56 NATO 1/7
http://www.box.net/shared/static/3vibt7g94a.jpg
The barrel has an “F” marked front sight base and a side sling swivel. The “F” mark is located on the port side of the front sight base.
http://www.box.net/shared/static/vthg89r4uq.jpg
http://www.box.net/shared/static/55o3qsd633.jpg
The SOCOM barrel will have a “date code” located immediately aft of the handguard retaining ring. The handguard retaining ring itself will also have cut-outs located at 4:30 and 8:30; again for the attachment of an M203.
http://www.box.net/shared/static/dm7yx5o0r9.jpg
The barrel will also have a small “O” stamp, that is located at the chamber section of the barrel, indicating a chrome-lined chamber and bore.
http://www.box.net/shared/static/3eoi24l667.jpg
Naturally, the SOCOM barrel will have M4 feedramps and there will be a numeral “4” stamped at the 3 o’clock position on the barrel extension.
http://www.box.net/shared/static/uu0b9h482l.jpg
Here are a couple pics comparing the SOCOM barrel to the standard M4 barrel.
http://www.box.net/shared/static/7c6rn7lhez.jpg
http://www.box.net/shared/static/65p2ey76g9.jpg
Accuracy Evaluation
I performed an accuracy (technically precision) evaluation of the Colt SOCOM barrel following my usual protocols. All shooting was conducted from a concrete bench-rest from a distance of 100 yards (confirmed with a laser rangefinder.) For the accuracy evaluation, the barrel was free-floated using a Daniel Defense Omega rail.
http://www.box.net/shared/static/pc5x4tu58z.jpg
The accuracy evaluation used statistically significant shot-group sizes and every single shot in a fired group was included in the measurements. There was absolutely no use of any Group Reduction Techniques (e.g. fliers, target movement, Butterfly Shots).
As many of the significant variables as was practicable were controlled for. The free-float handguard of the carbine rested in a Sinclair Windage Benchrest, while the stock of the carbine rested in a Protektor bunny-ear rear bag. Sighting was accomplished via a Leupold VARI-X III set at 25X magnification and adjusted to be parallax-free at 100 yards. Wind conditions on the shooting range were continuously monitored using a Wind Probe. The set-up was very similar to that pictured below.
http://www.box.net/shared/static/xo4duzdgtp.jpg
The Wind Probe.
http://www.box.net/shared/static/lkg47ptc04.jpg
Using match-grade hand-loads topped with Sierra 55 grain BlitzKings, I fired three 10-shot groups from the Colt SOCOM barrel in a slow, steady manner from 100 yards. Those groups had extreme spreads of:
0.90”
1.02”
0.93”
for a 10-shot group average extreme spread of 0.95”. All three of the 10-shot groups were over-layed on each other using RSI Shooting Lab to form a 30-shot composite group. The mean radius for the composite group was 0.35”.
The smallest 10-shot group.
http://www.box.net/shared/static/r9jgrq14zn.jpg
The 30-shot composite group.
http://www.box.net/shared/static/rbirjox05r.jpg
....
Submariner
01-02-11, 06:48
http://www.box.net/shared/static/in8cal2pcg.jpg
....
Were these shot with free-floated barrels? If not, would you expect the mean radius to be smaller with free-floated barrels?
ETA: What ammunition did you use?
RogerinTPA
01-02-11, 09:33
Thanks for the data on the SOCOM barrel Molon. Very informative as usual. It confirms my suspicion as to the accuracy of a quality milspec barrel, based on barrel profile.
Were these shot with free-floated barrels? If not, would you expect the mean radius to be smaller with free-floated barrels?
ETA: What ammunition did you use?
The barrels were all free-floated for testing. The ammunition used was match-grade hand-loads.
Guntrician
01-08-11, 13:36
Excellent illustrations as usual Molon. Thanks for your great posts.
The 6920 is a great rifle. I have to agree with those that said they are falling out of favor with the M4 profiled barrel. Although I have many M4s I do think a different profile would make sense. Just my opinion though.
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions, Inc. All rights reserved.