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Posted: 5/9/2003 7:30:11 AM EDT
I'm new to AR-15's so please be patient with me. I know barrel length must impact accuracy. My question is how much of an accuracy difference do you find from a heavy 16" barrel and a heavy 20" barrel? Is it reasonable to expect a 16" barrel to shoot 1 moa or better, or does it take a 20" or longer to reach that level of accuracy?

I'm confident that barrel brand and the ammunition used also factor into it. If there are more accurate brands of barrels, I'd love to know which ones.

Thanks,
Shane
Link Posted: 5/9/2003 7:43:38 AM EDT
IMHO a longer barrel is not more inherently accurate than a shorter barrel, all other things being equal. In fact, there is much evidence to support the claim that the shorter barrel of the same diameter might be more accurate because the shorter barrel will be stiffer, therefore less prone to deflect causing a phenomenon known as muzzle whip. Of course, a longer barrel may give better accuracy than the shorter one if the load being fired uses a relatavely slow burning powder that might not be completely burned in the short tube, but that is a question of reloading choices.
Link Posted: 5/9/2003 11:09:27 AM EDT
Only reason i chose a 20" barrel over the 16" was because the 16 is really loud, and you get extra velocity out of a longer barrel, which in theory makes it shoot flatter.
Link Posted: 5/9/2003 11:42:34 AM EDT
[Last Edit: 5/9/2003 11:46:03 AM EDT by Green0]
The velocity on a 24inch barrel is sweet. The longer barrels are used for long range competition because they tend to keep the bullet stailized at extreme range (like a 30cal rifle out at 1600meters using a 28-30inch barrel) I would guess this is caused by high velocity bullets getting more consistent spin rates with the longer barrels but I'm not sure. But with Ar's you probably won't shoot farther than 600-700meters so the 16 and 20inch barrels will be similar in accuracy. [b]the 16inch barrel has a carbine gas tube though which will cause recoil spike to be MORE SPIKEY and less smooth which might be a slight concern if you like the less recoil[/b]
Link Posted: 5/9/2003 12:07:36 PM EDT
Thanks for the info. From your responses, accuracy within 500 yards (I can't see a need for longer ranges right now) wouldn't be very different for either barrel length. I'm still not sure, but I'll proabably go with the 20" barrel for the noise factor and the slight edge on accuracy. I've got the itch to build myself an AR-15 (my first), but I can't decide on whether I want the shorter or longer barrels. Maybe, I'll just build one complete rifle and then buy an extra upper with a different length barrel. Thanks, Shane
Link Posted: 5/10/2003 7:16:30 AM EDT
As far as inherent accuracy goes, the above responses are spot on. Practical accuracy with iron sights may be an issue, depending on your eyesight. For some, the longer sight radius of the 20" offers a better sight picture and hence better accureacy. With optics, this is a moot point. As far as achieving 1 moa accuracy, either barrel length is capable, but it is a rare non free floated, chrome lined mil spec barrel that can do it. Most of these will typically run 1.5-2 moa. To do sub moa, you will probably need a "match" stainless steel barrel with a free float handguard.
Link Posted: 5/10/2003 10:38:10 AM EDT
The bullet is quite a few feet out of the barrel before the gas system begins to move the bolt carrier. Even with the carbine, this is not an accuracy consideration, though the higher gas port pressure does cause other functioning probems... thus Armalite's move to the mid length handguards, more forward front sight. Yes, barrel whip, or vibration. The short barrel will be stiffer than a longer barrel of the same diameter. Most of the accuracy differences from the 16" to the 20" are due to sight radius. As stated above, with optics, a non issue. I had noticed years ago that I shot as accurately with my 16" as my 20".
Link Posted: 5/11/2003 2:20:38 PM EDT
Originally Posted By bsbg: As far as inherent accuracy goes, the above responses are spot on. Practical accuracy with iron sights may be an issue, depending on your eyesight. For some, the longer sight radius of the 20" offers a better sight picture and hence better accureacy. With optics, this is a moot point. As far as achieving 1 moa accuracy, either barrel length is capable, but it is a rare non free floated, chrome lined mil spec barrel that can do it. Most of these will typically run 1.5-2 moa. To do sub moa, you will probably need a "match" stainless steel barrel with a free float handguard.
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Thanks for the input. My eyesight isn't the greatest, so I'll probably get some basic optics when I build my rifle. I'll just free float the barrel, and I'll have the accuracy I need with the 16" heavy barrel. You guys are great for newbies like me. I'm glad I found this web sight. Shane
Link Posted: 5/11/2003 3:02:12 PM EDT
You dont need a HBAR to get sub MOA accuracy. Several people here have gotten sub MOA groups using the M4 barrel profile. Of course this requires a free floated barrel, new trigger and preferably match grade ammo but it can be done. If all you want is sub MOA accuracy dont get an HBAR as you will just have unneeded weight.
Link Posted: 5/12/2003 7:18:43 AM EDT
Really, all I want is something with good inherent accuracy. Around 1 MOA seems great. Sub MOA accuracy is probably overkill as far as my needs go. I'm not looking to win paper punching tournaments, but I'd like to consistantly hit what I aim at out to 400-500 yards. I'm too new to this rifle to want more than that. From what I've read on this forum, most basic AR-15 setups are already as accurate as I want. I just didn't know that a 16" barrel was capable of such accuracy. It's amazing to me.
Link Posted: 5/12/2003 5:06:47 PM EDT
Be sure and read the [url=ammo-oracle.com]Ammo-Oracle[/url]
Link Posted: 5/13/2003 8:26:42 AM EDT
How about considering a fluted HBAR? According to Kurt's website, a 16inch fluted heavy barrel weighs 2.3pounds and a 16inch M4 barrel weighs 2.2pounds (i.e., only 0.1pound difference). Then you can have the added thickness of the hbar to reduce barrel whip while keeping the weight light like an M4 barrel. Mako
Link Posted: 5/18/2003 4:43:52 AM EDT
Check out the Bushmaster 16" fluted HBar. I purchased a 16" A3 upper for my preban shorty lower. It is very balanced, does not feel like an HBar.
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