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Colt 6520 Accuracy Evaluation (Page 1 of 2)
Posted: 2/27/2010 7:10:55 PM EDT
[Last Edit: Molon][Edited]
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Colt 6520 Accuracy Evaluation Attached File The 16” barrel found on the Colt 6520 has been the de-facto standard for what constitutes a light-weight 16" carbine barrel for decades. This barrel profile is affectionately referred to as a "pencil" barrel (cause John Wick once killed three men in a bar with one.) The profile is just a shortened version of the 20" barrel found on the Colt M16/M16A1. This 16" light-weight barrel is also the same barrel that is found on the Colt 6720. Colt 20" M16A1 barrel Attached File Colt 6520 barrel Attached File The Colt light-weight barrel has a barrel diameter of 0.625” at the gas block and approximately 0.57” forward of the gas block. The barrel profile has a slight taper underneath the handguards from the chamber to the gas block with an average diameter of approximately 0.64”. The stripped light-weight barrel weighs approximately 1 pound, 6 ounces. The light-weight barrel is chrome lined, has a NATO chamber and a 1:7” twist. This barrel employs a carbine gas system and has M4 feedramps. This accuracy evaluation was performed with a LaRue Tactical free-float handguard installed. Colt 6520 upper Attached File Colt 6520 converted to a flat-top (6720) with a Colt M4 upper receiver Attached File The test vehicle. Attached File The barrel stamp. Attached File M4 feed ramps Attached File Shooting was conducted from a concrete bench-rest using a Sinclair Windage Bench Rest in front and a Protektor bunny-ear bag under the stock. The ammunition used; match-grade hand-loads topped with Sierra 55 grain BlitzKings. Sighting was performed using a Leupold VAR-X III with a mirage shade. Magnification was set at 25X and the scope was adjusted to be parallax free at 100 yards. Wind conditions were monitored using a Wind probe. The set-up looked very similar to that pictured below. Attached File The Wind Probe Attached File Six 10-shot groups were fired in a row in a slow and steady manner. Those groups had extreme spreads of: 1.18” 1.92” 1.28” 2.53” 0.96” 2.24” for an average extreme spread of 1.69”. Using RSI Shooting Lab, I over-layed all six groups on each other to form a 60-shot composite group. The composite group had a mean radius of 0.56”. The 60-shot composite group . . . Attached File Attached File Attached File ..... |
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Originally Posted By Molon:
Cousins . . . separated at birth. 
http://www.box.net/shared/static/cnigxk1m8b.jpg Awesomeness.....that is scary close  I must admit your T-1 stole the damn show I think the T-1 no matter what you put it on, is flat out one of the sexiest optics going. Perfect for that build as well.
eta....after seeing stone cold reliable numbers provided by you in this thread, one has to put the LW pencil profiled colt barrel in the top 3 of all time imho....note i am def. not a student like you guys, but as long as i have been shooting ARs, i have never found a barrel as light and accurate as the lw colt. Really i could listen or talk about the 6520 all day long and its basically cause of that awesome barrel. |
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Molon, If you don't mind me asking,( and its none of my business, if you'd rather not share.).. How do you find the time to conduct all these tests? I'm darn lucky if I can get a weekend of shooting in , let alone a days worth in a month.
Do you do this ( shooting- testing) for a living? How long have you been doing these tests? What was your first rifle? I'm jealous..... Thanks again, for all the excellent posts. |
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As always, Molon, top notch work. Nice to see the pencil barrels can hold their own just fine for accuracy.
Originally Posted By jcrowl:
Thanks for the info. That's good news since I have a 6520 on the way! Thank goodness! I was worrying that you were going to run short on AR's! 
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| kinda makes me wanna tear apart my colt a2 complete upper just simply for the barrel's ability. same lightweight barrel,1/7 chrome lined, 'cept it is pre-ban time frame. so i think that puts it before the m4's style of feed ramps.someone correct me if i'm wrong........ mine is from a 6530 so it does'nt have the bayonet mount. btw,.....thanks for the write up it's very informative. |
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Originally Posted By buxman66:
kinda makes me wanna tear apart my colt a2 complete upper just simply for the barrel's ability. same lightweight barrel,1/7 chrome lined, 'cept it is pre-ban time frame. so i think that puts it before the m4's style of feed ramps.someone correct me if i'm wrong........ mine is from a 6530 so it does'nt have the bayonet mount. btw,.....thanks for the write up it's very informative. I could be wrong but i am pretty sure any older def. wouldnt have the ramps. I think A2s are all or nothing..either you love them or you hate them. I loved the 6520, but hated to use the a2 sight, and for me at least i dont get any utility outta carrying my rifle by a handle cause i am not in combat with it 
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Originally Posted By bfoosh06:
Molon, If you don't mind me asking,( and its none of my business, if you'd rather not share.).. How do you find the time to conduct all these tests? I'm darn lucky if I can get a weekend of shooting in , let alone a days worth in a month. Do you do this ( shooting- testing) for a living? How long have you been doing these tests? What was your first rifle? I'm jealous..... Thanks again, for all the excellent posts. I don’t shoot for a living, but I do live to shoot! I try to get to the range at least once a week (although it doesn’t always work out that way.) In the summer, it’s not uncommon for me to hit the range 2 or 3 times a week.
My first rifle was a Colt 6520, purchased during the AW ban. (I figured that if Bill Clinton was doing his best to prevent me from owning one of these, it was something that I really ought to have!) I began my testing and evaluations approximately 7 years ago after making repeated observations at the range, of both my shooting and many others, that just didn’t match up with what I was reading in gun-rags and on firearms forums on the Internet. |
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Originally Posted By buxman66:
same lightweight barrel,1/7 chrome lined, 'cept it is pre-ban time frame. so i think that puts it before the m4's style of feed ramps. My first 6520 was a pre-ban and it had M4 feed ramps. |
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Originally Posted By Molon:
Originally Posted By buxman66:
same lightweight barrel,1/7 chrome lined, 'cept it is pre-ban time frame. so i think that puts it before the m4's style of feed ramps. My first 6520 was a pre-ban and it had M4 feed ramps. 
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Did you wait any longer in between shots than any of your other tests? For heat dissipation. I'm assuming no, but just curious.
Great write up as always. I had a lw 20" A1 that shot really well also. I would thing for 99% of the shooting most people do, this is good enough. If I ever build an AR, it's going to be with a LW barrel. |
| That's pretty interesting. I wonder if the free float handgaurd helps dissipate heat more quickly than a regular handguard. I don't know if I've ever noticed a difference, but I don't have a free floated skinny barrel. Plus admittedly, I usually shoot 5 rounds. DOH! |
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I did a similar test with a Colt pencil barrel over the weekend also. The barrel was from a Colt 723- 14.5" pencil barrel, 1/7 twist. I was a bit shocked by the results. Its bone stock, reg. handg. etc.. I slapped a POS Tasco scope I had sitting in my garage on it to test it out. I was more or less just function testting it and figured I may accuracy test while I was out. Anyway, with some handloads I use in another rifle (24 gr. R-15 and 77 SMK's) with 5 rds groups it was shooting right at 1 inch at 100 yads. This is off a back pack. With Black Hills 75 gr. seconds it grouped right at 2", 55 grn. LC ammo about the same 2"
Pretty impressed with a 14.5" pencil barrel. So, if anyone thinks that pencil barrels will not be accurate........ here are some examples they are good to go. |
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Originally Posted By FrankSL:
I think the most underrated element of Colt is the quality of their barrels. That may be so, but the colt barrel I have is the least accurate and shift in POI between ammo is drastic. It's annoying. I've actually had better luck with wilson, RRA and WOA for accuracy. |
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Originally Posted By bcw107:
I'm curious what the accuracy would have been with the T-1 and its 4 MOA dot rather than the Leupold. left click |
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Originally Posted By FrankSL:
I think the most underrated element of Colt is the quality of their barrels. The barrel on the Colt 6721 is the most accurate "off the shelf" chrome-lined, NATO chambered AR-15 barrel that I've tested. 
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Originally Posted By Molon:
Originally Posted By FrankSL:
I think the most underrated element of Colt is the quality of their barrels. The barrel on the Colt 6721 is the most accurate "off the shelf" chrome-lined, NATO chambered AR-15 barrel that I've tested. http://www.box.net/shared/static/5v2ke9eaym.jpg Wow, that is one helluva statement considering your time on diff. barrels......I hope that you will continue to try and work this barrel in with various ammo tests or whatever because it is great to see the data that supports what I always suspected
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Originally Posted By TRIDENT1982:
Originally Posted By Molon:
Originally Posted By FrankSL:
I think the most underrated element of Colt is the quality of their barrels. The barrel on the Colt 6721 is the most accurate "off the shelf" chrome-lined, NATO chambered AR-15 barrel that I've tested. http://www.box.net/shared/static/5v2ke9eaym.jpg Wow, that is one helluva statement considering your time on diff. barrels......I hope that you will continue to try and work this barrel in with various ammo tests or whatever because it is great to see the data that supports what I always suspected I've owned four of the 6721 barrels so far and they have all shot well. My current one has over 3000 rounds through it and turned in this 10-shot group from 100 yards this last weekend. 
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All that is necessary for Trolls to flourish, is for good men to do nothing.
In God We Trust. Everyone else needs to post data.
In God We Trust. Everyone else needs to post data.
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Originally Posted By Molon:
Originally Posted By TRIDENT1982:
Originally Posted By Molon:
Originally Posted By FrankSL:
I think the most underrated element of Colt is the quality of their barrels. The barrel on the Colt 6721 is the most accurate "off the shelf" chrome-lined, NATO chambered AR-15 barrel that I've tested. http://www.box.net/shared/static/5v2ke9eaym.jpg Wow, that is one helluva statement considering your time on diff. barrels......I hope that you will continue to try and work this barrel in with various ammo tests or whatever because it is great to see the data that supports what I always suspected I've owned four of the 6721 barrels so far and they have all shot well. My current one has over 3000 rounds through it and turned in this 10-shot group from 100 yards this last weekend. http://www.box.net/shared/static/10bptgnptv.jpg NUFF SAID
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To the OG gangsters of "BADNESS".."Mr. Clip", "Micro Man", and to the "Godfather" himself, THANKS for fueling my dreams!
The "Unicorn Man" and The "Sir"....Fuel accepted!
The "Unicorn Man" and The "Sir"....Fuel accepted!
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Originally Posted By vicious_cb:
I wonder how an M4 profile would stack up I've actually evaluated several of the M4 profile barrels, but unfortunately I lost a lot of data due to a hard-drive crash. I'll see if I can dig up some hard copy targets from the M4 profile barrels. |
All that is necessary for Trolls to flourish, is for good men to do nothing.
In God We Trust. Everyone else needs to post data.
In God We Trust. Everyone else needs to post data.
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Originally Posted By twoofswords:
Thank you for taking the time to conduct this test! I'm strongly interested in a light weight AR build and this test definitely confirms that I'm not neutering my AR by doing such. SET YOURSELF FREE 
The Colt pencil profile is worth doing a build around for sure imho
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To the OG gangsters of "BADNESS".."Mr. Clip", "Micro Man", and to the "Godfather" himself, THANKS for fueling my dreams!
"Unicorn Man", The "Sir", "Stamp Man"....Fuel accepted!
"Unicorn Man", The "Sir", "Stamp Man"....Fuel accepted!
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Molon, have you tuned any ammo for these?
How much more accuracy do you think you could get with hand made match tuned for this weapon? TXL |
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| I have the same brl and it shoots great with .223 Hornady "Match" 75Gn BTHP in the 25Rnd boxes. The TAP version and the T2 version, not so well. |
Nothing in this post should be considered information posted in an official capacity. It is the authors personal opinion alone.
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I bought my wife this Carbon AR from Bushmaster and I'm curious about the possibility of switching out the barrel for the Colt LW.
First off will this barrel even fit the BM? I didn't know if the carbon guns are any different. Is there any weight savings? I can't find any info on the weight of the BM "lightweight" barrel. My wife is small so every little bit helps The weight of this gun is why I purchased it for her. I'm sure it is better than the factory barrel, hopefully it is lighter, so I don't really see a downside to the idea. ETA- BM Barrel Info 16" Bushmaster SuperLight Barrel Assembly The lightest 16" barrel we've ever offered - tapers from .670" to .565" under handguards, .625" under sightbase, and to .570" at the muzzle - similar to the original Vietnam era A1 barrel profile. Assembly includes Bayonet Lug, Threaded Muzzle, A2 Birdcage Flash Suppressor, Handguards, Gas Tube, and Delta Ring Kit. NOTE: due to diameter at muzzle, no "slip-on/pinned" type muzzle brakes will fit this barrel. Use only 1/2"x 28 T.p.I. threaded accessories. Grove |
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Grove, the BM Superlight is probably as light as you'll get. While I have both Colt LTWTs and BM Superlights, I've never compared them by weight; but I don't think the Colt is any lighter.
If you have a factory carbon upper, then I believe they use a different barrel extension specific to that receiver in which case a barrel swap will be problematic. |
Colt 6520 Accuracy Evaluation (Page 1 of 2)
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