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Many people get like to configure their AR's with 16" barrels since it's more compact. However, how much better in terms of terminal ballistics is the 20" over the 16"? How does it effect the effective range? What about velocity out of the barrel?

Thanks guys, I know I can always count on you for info!
 

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With ambient temps about 80, my 50gr. V-Max varmint load (using AA2230) averages 3000 fps from a 16" upper and 3300 fps through a 24" upper (and 50 fps more than that from a 24" Remington 700V).

Now you've got me curious what it'll do in a 20" AR barrel. Something else to look forward to when it warms up.
 

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There was an article in USPSA's Front Sight magazine, a couple of years ago, concerning the loss of velocity with loss of 4" of barrel. USPSA has a minumum power floor for rifle competition, and tests indicated that 16" barrels often don't make the minimum with factory 55gr. ammo. That would mean the velocity is right around 2700-2750. I have yet to shoot a match that chrono'd rifles, so I suspect HQ isn't too concerned about it.
In terms of terminal ballistics, I have read some stuff that indicates the .223 round loses a whole lot of its effectiveness, in military use, if the velocity drops much below 2700fps, and that's been an issue with the M4 Carbine and the current M855 round, which has a muzzle velocity not much above that, out of a 14.5" barrel. Of course, civilians have access to all sorts of trick ammo that the military doesn't (by law, anyway), which may redress some or all of that.
 

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There was an article in USPSA's Front Sight magazine, a couple of years ago, concerning the loss of velocity with loss of 4" of barrel. USPSA has a minumum power floor for rifle competition, and tests indicated that 16" barrels often don't make the minimum with factory 55gr. ammo. That would mean the velocity is right around 2700-2750.
Is this for commercial .223 ammo? I would expect 5.56mm milspec 55 gr ammo (M193 or Q3131A) to be substantially faster than that out of a 16" barrel. Most of the things Ive read state like 2900-3000 fps out of a 16" barrel with M193/Q3131A.

Commercial .223 ammo is a joke I dont get why its loaded so much weaker. I admit I havent measured the difference but I can see it hear it and feel it for sure.
 

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Velocity is critical in getting 5.56 to do it's job. I dislike M4 14.5" barrels. My Steyr AUG is the same length as 10.5" Commando and I have 6" more barrel and a full stock. I believe the Marine Corps M16A4 is the best of the service rifle/carbines in that platform.
 

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Of course, your specific application is important to consider. In USPSA competition (like RickB notes) I have never seen the officials test velocity in my region, so everyone uses 16" barrels for multigun matches. At ranges up to 330 yards in that form of competition, the 16" AR hits targets as well as any 20" or 24" rifle. I've used all three barrel lengths and prefer the 16 for ease of handling in a course of fire. That's the limit of my experience. I don't shoot in combat like some of you, so I don't pretend to be an expert in it.
 

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With like ammo being used the difference would typically be less than 150fps, which in the long run that ain't much. The difference would show itself if you were talking about a match grade barrel compared to a regular production barrel, and then the difference isn't fps but how accurate one is to the other. Personally I wouldn't be too concerned if you were talking production barrels, take the short one and run. If your need was for a target rifle then I would go with the 20"er, but only if I was planning on some long lead slinging.
 

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IIRC the 20 will give you a 150 yd advantage over the 14.5.
I had a chart, but I cant find it. I'll see if I can dig it up in the next day or two.
 

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Is this for commercial .223 ammo? I would expect 5.56mm milspec 55 gr ammo (M193 or Q3131A) to be substantially faster than that out of a 16" barrel. Most of the things Ive read state like 2900-3000 fps out of a 16" barrel with M193/Q3131A.

Commercial .223 ammo is a joke I dont get why its loaded so much weaker. I admit I havent measured the difference but I can see it hear it and feel it for sure.
Brass on military cases is thicker to accomodate higher pressures.
 
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