User Panel
User Panel
User Panel
|
Posted: 2/27/2010 7:10:55 PM EDT
[Last Edit: Molon]
Colt 6520 Accuracy Evaluation
 Attached FileThe 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 FileColt 6520 barrel  Attached FileThe 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 FileColt 6520 converted to a flat-top (6720) with a Colt M4 upper receiver  Attached FileThe test vehicle.  Attached FileThe barrel stamp.  Attached FileM4 feed ramps  Attached FileShooting 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 FileThe Wind Probe  Attached FileSix 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..... |
|
|
|
|
Posted: 2/27/2010 7:25:16 PM EDT
[#1]
Thanks for the info. That's good news since I have a 6520 on the way!
|
|
|
|
|
Posted: 2/27/2010 7:58:02 PM EDT
[#2]
I love the overwhelming amount of data you provide.
|
|
|
|
OK, USA
|
Posted: 2/28/2010 6:42:31 AM EDT
[#3]
Thanks for posting great information I love my 6520.
|
|
|
|
Posted: 2/28/2010 6:57:19 AM EDT
[#4]
I did a similar thing....just swapped the colt a2 with a BCM m4 and added a MI car length free float rail. I just didnt chop the FSP. Excellent info buddy...who doesnt like a post about a 6520 pencil barrel though
|
|
|
|
|
Posted: 3/2/2010 7:51:22 PM EDT
[#5]
Originally Posted By TRIDENT1982:
Cousins . . . separated at birth. 
|
|
|
|
VA, USA
|
Posted: 3/2/2010 8:23:00 PM EDT
[#6]
Excellent post. Thank you for sharing.
|
|
|
|
Posted: 3/2/2010 8:23:14 PM EDT
[Last Edit: TRIDENT1982]
[#7]
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. |
|
|
|
WV, USA
|
Posted: 3/2/2010 11:14:56 PM EDT
[#8]
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. |
|
|
|
Posted: 3/2/2010 11:40:42 PM EDT
[#9]
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!
|
|
|
|
|
Posted: 3/2/2010 11:53:21 PM EDT
[#10]
Nice write up. Thanks much.
|
|
|
|
OH, USA
|
Posted: 3/3/2010 1:02:04 AM EDT
[Last Edit: buxman66]
[#11]
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.
|
|
|
|
Posted: 3/3/2010 11:20:44 PM EDT
[#12]
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 
|
|
|
|
|
Posted: 3/4/2010 4:15:29 PM EDT
[Last Edit: Molon]
[#13]
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. |
|
|
|
|
Posted: 3/21/2010 12:31:44 PM EDT
[Last Edit: Molon]
[#14]
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. |
|
|
|
|
Posted: 3/25/2010 9:15:41 PM EDT
[Last Edit: Molon]
[#15]
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. 
|
|
|
|
TX, USA
|
Posted: 3/25/2010 11:38:22 PM EDT
[#16]
Ive wanted a 6520 for a while.Its nice to see some tech in this forum and not just pictures.
|
|
|
WI, USA
|
Posted: 3/26/2010 11:13:11 AM EDT
[#17]
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. |
|
|
|
Posted: 4/4/2010 11:07:52 AM EDT
[#18]
Originally Posted By JJREA:
Did you wait any longer in between shots than any of your other tests? For heat dissipation. I'm assuming no, but just curious. Correct. |
|
|
|
WI, USA
|
Posted: 4/5/2010 12:30:05 AM EDT
[#19]
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!
|
|
|
WA, USA
|
Posted: 4/5/2010 12:47:13 AM EDT
[Last Edit: Rocker]
[#20]
Nice report.
The Colts I've shot where all over the place when the barrel got warm (few shots) I'm sure your reloads and the free float helps quite a bit. I do want another LW but not for any target work!
|
|
|
NM, USA
|
Posted: 4/5/2010 11:50:29 AM EDT
[#21]
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. |
|
|
|
Posted: 4/11/2010 9:33:45 PM EDT
[Last Edit: MRW]
[#22]
I love me a pencil barrel.
  |
|
|
|
|
Posted: 4/15/2010 8:02:01 PM EDT
[#23]
Originally Posted By JJREA:
That's pretty interesting. I wonder if the free float handgaurd helps dissipate heat more quickly than a regular handguard. Where's 87GN?
|
|
|
|
|
Posted: 4/15/2010 10:12:28 PM EDT
[#24]
I'm curious what the accuracy would have been with the T-1 and its 4 MOA dot rather than the Leupold.
|
|
|
|
|
Posted: 4/15/2010 10:14:25 PM EDT
[#25]
I think the most underrated element of Colt is the quality of their barrels.
|
|
|
|
WI, USA
|
Posted: 4/17/2010 5:00:56 PM EDT
[#26]
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. |
|
|
|
Posted: 4/22/2010 5:49:25 PM EDT
[#27]
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 |
|
|
|
|
Posted: 5/1/2010 11:40:46 PM EDT
[#28]
Originally Posted By jcrowl:
Thanks for the info. That's good news since I have a 6520 on the way! Pics? |
|
|
|
|
Posted: 5/2/2010 12:42:56 AM EDT
[#29]
Another nice tid bit of info.
|
|
|
|
|
Posted: 6/3/2010 5:31:39 PM EDT
[Last Edit: Molon]
[#30]
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. 
|
|
|
|
|
Posted: 6/12/2010 4:53:29 PM EDT
[#31]
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
|
|
|
|
|
Posted: 6/15/2010 3:38:48 PM EDT
[Last Edit: Molon]
[#32]
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. 
|
|
|
|
|
Posted: 6/15/2010 4:01:53 PM EDT
[Last Edit: TRIDENT1982]
[#33]
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
|
|
|
|
USA
|
Posted: 6/26/2010 5:06:03 PM EDT
[#34]
I wonder how an M4 profile would stack up
|
|
|
|
Posted: 7/4/2010 11:42:06 AM EDT
[#35]
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. |
|
|
|
FL, USA
|
Posted: 7/8/2010 10:12:00 PM EDT
[#36]
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. |
|
|
|
Posted: 7/8/2010 10:25:18 PM EDT
[#37]
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
|
|
|
|
|
Posted: 7/8/2010 11:09:16 PM EDT
[#38]
Originally Posted By 87GN:
I love the overwhelming amount of data you provide. +1 Molon, you and 87GN have some of the best posts on Arfcom. |
|
|
|
|
Posted: 8/21/2010 2:56:07 PM EDT
[#39]
My first AR was a light gray Colt Sporter Lightweight (R6530) with the little 16in "Pencil" barrel. Everyone who I let shoot it, loved it. From LE/Military to women and kids. And yes, it was as accurate!
|
|
|
|
|
Posted: 10/14/2010 10:37:07 PM EDT
[#40]
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 |
|
|
|
|
Posted: 10/14/2010 11:27:31 PM EDT
[#41]
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.
|
|
|
|
|
Posted: 1/8/2011 4:54:17 PM EDT
[#42]
|
|
|
|
|
Posted: 4/11/2011 9:47:46 PM EDT
[#43]
BUMP!
|
|
|
|
|
Posted: 12/18/2011 12:21:11 PM EDT
[Last Edit: Grove]
[#44]
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 |
|
|
|
|
Posted: 12/18/2011 12:57:26 PM EDT
[#45]
A lot of folks underestimate the accuracy of a lt wt bbl. This little thread helps prove that they are nothing to be taken lightly.
|
|
|
|
|
Posted: 12/18/2011 3:43:39 PM EDT
[#46]
Good report Molon. Thanks for taking time to do it.
|
|
|
|
|
Posted: 12/18/2011 3:57:30 PM EDT
[#47]
Nice writeup as always Molon.
Quick question. When using a free floating rail that is resting on a shooters rest, do you get a shift in POI when using irons with the front sight mounted on the rail itself? |
|
|
|
|
Posted: 12/18/2011 5:01:28 PM EDT
[#48]
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. |
|
|
|
USA
|
Posted: 1/4/2012 6:42:32 PM EDT
[#49]
bump for awesome thread!
|
|
|
WV, USA
|
Posted: 1/4/2012 6:52:01 PM EDT
[#50]
Awesome thread! About to buy a barrel with the same profile, exactly what I was looking for!
Also.... Damn, JCrowl, your getting another AR? What is this AR number 672852??
|
|
|
Win a FREE Membership!
Sign up for the ARFCOM weekly newsletter and be entered to win a free ARFCOM membership. One new winner* is announced every week!
You will receive an email every Friday morning featuring the latest chatter from the hottest topics, breaking news surrounding legislation, as well as exclusive deals only available to ARFCOM email subscribers.
AR15.COM is the world's largest firearm community and is a gathering place for firearm enthusiasts of all types.
From hunters and military members, to competition shooters and general firearm enthusiasts, we welcome anyone who values and respects the way of the firearm.
Subscribe to our monthly Newsletter to receive firearm news, product discounts from your favorite Industry Partners, and more.
Copyright © 1996-2024 AR15.COM LLC. All Rights Reserved.
Any use of this content without express written consent is prohibited.
AR15.Com reserves the right to overwrite or replace any affiliate, commercial, or monetizable links, posted by users, with our own.
