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Old February 15, 2013, 10:02 AM   #1
Skans
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Advantages of 20" AR Barrel???

I have an older AR/M16 barrel laying around so I decided to use it in my AR build. However, I have some technical questions about this barrel. It's a 20" Colt "Government Profile", chrome bore 1/7 twist. I bought it new at a gun show in the early '90's - and although I mounted it on an A2 Upper, it's never been used.

Question 1: I see most people using carbine length barrels these days for AR builds - hardly ever see any 20" barrels. Why is this? Is there any real advantage gained by using a 20" barrel. I figured I could gain a little more range with the longer barrel.

Question 2: Are these older government profile barrels harder to find; or is there anything that makes them obsolete? I've already decided that I'm going to free-float the barrel and replace the old-style front sight tower with a low-profile gas block.

Question 3: I want to use a collapsible stock system, but am concerned that the rifle will feel muzzle heavy. What can I do to get a more balanced feel, but still have a stock that is adjustable?
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Old February 15, 2013, 10:23 AM   #2
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A 20' barrel will mean higher velocity, and a more accuracy at longer range. Shooting the AR at extended ranges, the 150 to 200 fps loss in velocity make make a big difference in bullet performance in terms of how the bullet acts when it hits it's target. In terms of accuracy, the shorter barrel is 'stiffer' and introduces less "whip" than the longer barrel, which affects accuracy. However, the shorter barrel can not generate the higher bullet velocities that a longer barrel can, which in turn affects bullet drop much more than the longer barrel. The 20'' will generate better velocity, which translates to better accuracy at long distance along with better terminal performance. Perhaps this why I have never seen a carbine used at a competition match.
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Old February 15, 2013, 10:51 AM   #3
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I use a 20 inch barrel both with a fixed and collapsible stock they both feel good to me. Mine is outfitted with a free float quadrail I really like it for 3 gun and other similar matches most people run 18 or 16 inche but I like the extra lethality of the longer barrel increases the distance of fragmentation of 55 grain fmj's to 250 meters
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Old February 15, 2013, 11:44 AM   #4
Art Eatman
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I'm not particularly interested in combat or coolness. The effectiveness of a .223 is velocity, so I'll take a 20" as better for hunting and general shooting.
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Old February 15, 2013, 12:21 PM   #5
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Post belongs in the Semi Auto group.
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Old February 15, 2013, 02:23 PM   #6
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Sorry, I mistakenly posted in the wrong forum - can one of the mods move this to semi-auto rifles?
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Old February 15, 2013, 02:45 PM   #7
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Considering that Art has already commented in this thread, the moderator for this sub-forum, I dont think it needs moving...
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Old February 15, 2013, 03:50 PM   #8
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A 20" barrel offers a longer sight radius and higher velocity, both important when the target is 200 or more yards away. A 16" barrel is more portable and maneuverable, but it uses a shorter gas system and therefore a shorter sight radius. Many people prefer the shorter barrel for lower weight, but in doing so they sacrifice the advanatages of higher velocity and sight radius for convenience. But since most people shoot at 100yds, and the sights work just fine for going bang, they never know the difference.
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Old February 15, 2013, 05:15 PM   #9
Skans
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I do appreciate the information. I have other .223's that I use for less than 100 yard distances. I would actually rather have the longer barrel on the rifle I'm putting together. The biggest thing I'm concerned with, however, with the longer barrel is balance. A really light weight stock is going to make the thing muzzle heavy, especially with a free floating aluminum rail system.
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Old February 15, 2013, 06:10 PM   #10
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With the rise in popularity of the heavy bullet, the velocity increase from the 20" bbl. will keep you supersonic longer, if you are motivated to take the long shot.
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Old February 15, 2013, 06:19 PM   #11
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A Magpul UBR or PRS will help balance the rifle.

Just some food for thought... You have the beginnings of a good iron sight platform. You might find you really enjoy the challenge.
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Old February 15, 2013, 08:31 PM   #12
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One of my favorite AR's is my 20" government profile upper with DD A1.5 rear sight mounted on a CAV arms polymer lower. It's the ultimate KISS AR IMHO.
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Old February 15, 2013, 10:17 PM   #13
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Hey, I never claimed perfection! I wuz looking at the question, not paying attention to which forum.
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Old February 15, 2013, 10:42 PM   #14
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Quote:
A 20" barrel offers a longer sight radius
That will only be true if the sights are installed in a way that takes advantage of the barrel length. There are so many options. I have seen a lot that have the front sight mounted in locations other than the end of the barrel.

So its certainly an option, and one that I would like.

I mention it because I was looking for one with a 20 barrel and long sight radius, and didn't find any affordable on my budget. That was before FireArmageddon. Now - no way.
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Old February 15, 2013, 11:13 PM   #15
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My 6.8 has a 20" fluted heavy barrel and I use an Ace Skeleton stock on it and it balances perfectly. I don't think you will have the balance problems that you think, especially if this is the standard A1 or A2 profile barrel.
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Old February 17, 2013, 08:10 AM   #16
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I have carbines and full length rifles. To me, the 20" guns have a different recoil and are smoother shooting. I use my 20" guns for the matches at my club.
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Old February 17, 2013, 08:27 AM   #17
Nathan
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IMO, good balance can be achieved by:
- using a plastic hand guard like Magpul MOE or A2
- have your barrel turned down under the hand guards and maybe out front by ADCO or similar.
- use some of the reasonably heavy stocks mentioned earlier.

Frankly, I would build it first without turning the barrel because that has some potential to hurt accuracy.
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Old February 18, 2013, 02:01 PM   #18
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Quote:
Mine is outfitted with a free float quadrail I really like it for 3 gun and other similar matches most people run 18 or 16 inche but I like the extra lethality of the longer barrel increases the distance of fragmentation of 55 grain fmj's to 250 meters
Okay... What are you saying here? Punctuation is your friend.

I shoot an 18" barrel for 3-gun, but at our matches there are plenty of 16" barrels as well, and an occasional 20" barrel. None of these guns have problems hitting the 650 yard target, some using 55 gr FMJ rounds.

If you think that it takes a 20" barrel to make a 55 gr projectile accurate at 250 yards then I question the experience that you have with the platform.

And I still have not figured out where "fragmentation" comes into this discussion from...


To the OP:

Quote:
A Magpul UBR or PRS will help balance the rifle.
This was going to be my recommendation. The PRS is not as adjustable as the UBR or other carbine stocks, but it is about perfect to balance out a 20" barrel.
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Old February 18, 2013, 02:24 PM   #19
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I was actually considering the Magpul UBR or PRS - so far, that's all I can come up with. If I understand correctly, the Magpul URB can't be to adjust along the buffer tube, just with the fine adjustments? Are these Magpul stocks really worth the price, or is there something truly as good for less money?
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Old February 18, 2013, 03:33 PM   #20
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Never said that you need a 20 inch barrel in order for the 5.56 round to be accurate past 250 meters, just that the extra velocity of the 20 inch allows the round to reach its full potential. Which is to yaw and fragment in flesh, which for me is a distinct advantage.

Other than that its all personal preference, but I personally have never found a 20 inch barrel AR to be unbalanced, in fact to me its smoother than my friends 16 inch carbines
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Old February 18, 2013, 03:41 PM   #21
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Quote:
Originally Posted by Skans
Question 2: Are these older government profile barrels harder to find; or is there anything that makes them obsolete? I've already decided that I'm going to free-float the barrel and replace the old-style front sight tower with a low-profile gas block.
I don't have anything useful to add, but wanted to note that this seems like a very useful configuration. I was looking for a barrel like yours and a cheap free float tube to make something reasonably light and reasonably accurate and that could be carried comfortably.

I was in the midst of my search for parts when the unpleasantness in Connecticut hit. I am not inclined to try to put anything together in the current environment, but I think your idea is great.
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Old February 18, 2013, 04:59 PM   #22
Skans
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This past weekend, I took off the sight tower/gas block and cut off the tower in hopes of being able to salvage the part. I decided to do this because the barrel was already drilled for this type of gas block, it saves me about $60 and was actually fun to do. shaped it, sanded it, polished it and then blued it with Casey's paste. The bluing actually came out ok, but overall the piece was just too shiny for the flat-black barrel. So, I ended up spraying it with some 500 degree flat black engine paint. Looks pretty good; I'll have to see how I like it when I have everything together.
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Old February 18, 2013, 05:43 PM   #23
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Quote:
If I understand correctly, the Magpul URB can't be to adjust along the buffer tube, just with the fine adjustments?
Negative, you have those backwards. The PRS is the stock with the fine adjustments. The UBR has a cheekweld that stays in place, but the stock will adjust back and forth on the buffer tube. The UBR also allows you to preset the stopping point. That way, when you set the "stop" at the 4th indexing point you can then contract the stock to make the OAL of the gun as small as possible. You can then extend it quickly and it will automatically stop at the 4th indexing point instead of passing it and going all the way to the rear like other retractable stocks.

PRS:



UBR:

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Old February 18, 2013, 07:16 PM   #24
JimDandy
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As someone who recently got their first AR and tried several different optics choices as well.. a 20 inch barrel allows for a longer tube. A 16 inch barrel with a fixed front sight tower will run into issues with bigger bells and longer tubes.

If I were involved in home defense. a 16 inch upper would be my choice. If I were doing match target comps at 300-600 yards I'd get the 20 inch upper.
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Old February 18, 2013, 08:20 PM   #25
CTS
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I really don't understand the concern with being muzzle heavy or unbalanced. The A2 stock that came on standard issue M16s with a 20 inch government profile barrel are no heavier than an adjustable carbine stock. As I said earlier, I am using an Ace skeleton stock which is lighter yet and it still is not muzzle heavy and balances quite nicely and that is with a 20" heavy barrel and aluminum rifle length free float tube. Barrel is fluted under the handguard. I just weighed the A2 stock that I took off to replace with the Ace and it weighs 13.2 oz. I can't imagine a collapsible stock being enough lighter than that to cause a muzzle heavy concern.
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Last edited by CTS; February 18, 2013 at 11:57 PM.
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