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bushmaster74 06-13-2014 12:59 AM

Ar barrel length
Wanting to do a barrel change on my cmmg. Was wanting to put on a 24" heavy barrel. What's the pros and cons of going that long. I like the look mainly but still want accuracy.

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fa35jsf 06-13-2014 02:04 AM

Well as it was mentioned a few days ago on another thread, a longer barrel does not necessarily mean greater accuracy. However, a longer barrel will mean faster muzzle velocities which translates into less drop and more energy at distance. According to this calculator with a 55gr bullet and an initial velocity of 3000fps, the increase in velocity from 16 to a 24 inch barrel is 230 fps.

fa35jsf 06-13-2014 02:18 AM

And so by Hornady's online tool, the 230fps increase will decrease the drop at 300 yards by 2.5 inches, 500 yards by 11.2 inches, and at 700 yards by a whopping 31.8 inches using the same bullet and powder. The above numbers are the result of this equation (24 inch barrel velocity - 16 inch barrel velocity). Remember that the actual drop is still quite great at those distances.

kbd512 06-13-2014 03:47 AM

The "pro" is that you like way the rifle looks.

The "con" is that the rifle is now as long as a battle rifle, it weighs as much as a battle rifle with worse weight distribution, and the velocity loss between 24 and 20 inches is minimal.

But hey, it's your money and ultimately you are the one who will be happy or unhappy. I'd say it may be useful as a moderate distance target rifle or perhaps open terrain hunting rifle, if your locale allows 5.56MM for hunting, and it squeezes every last ounce of juice outta the 5.56MM, but that's about it.

bushmaster74 06-13-2014 04:49 AM

I'm kinda goin for a bench rest / bipod rifle with this one. I know the longer / heavier barrel won't be a comfortable shouldered rifle Just kinda goin for look but shill want it too shoot good

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Highpower 06-13-2014 05:03 AM


Originally Posted by fa35jsf (Post 1589635)
..... the increase in velocity from 16 to a 24 inch barrel is 230 fpm.

I was with you there until I got to feet per minute.... ;)

It was a test to see if we're paying attention, right? :D

fa35jsf 06-13-2014 10:27 AM


Originally Posted by Highpower (Post 1589669)
I was with you there until I got to feet per minute.... ;)

It was a test to see if we're paying attention, right? :D

HAHA. Hey I was tired and just got done calculating fuel flow in pounds per minute.

bushmaster74 06-13-2014 11:11 AM

As far as looking like a battle rifle and heavy I don't mind. But it should still shoot fine right? On shelf ammo?

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Werminator 06-17-2014 05:50 PM

Bush, you will still have to find the right load for ultimate accuracy. Keep in mind also that every gun and every barrel is an individual and as such won't react equitably to all cartridges. Try several different loads methodically so as to find what load your weapon places on target most consistenly and base your results on that loading.

Sniper03 06-17-2014 06:30 PM


From experience, I would only recommend a 20" max length heavy varmint barrel for your rifle. The 24 is very front heavy. The other issue is it makes the rifle entirely too heavy to pack around incase you want to use it for something else other than stationary on a bench. Like for instance varmint or predator hunting. In addition it will shoot no better than the 20". I have had two Rock River Arms 20" A-4 Varmint Rifles both were 1/4 MOA guns when I was having a good day. Bottom line the 24 will do no better and heavy as stated. So my advise if you are going to go to a Heavy Barrel only go to the 20" even for bench shooting. Of course the quality of the barrel is important as well as selecting the barrel twist for the rounds you will be shooting. Mine were both 1:8 Twist Stainles Air Guaged Wildy Chambers. I mostly shot 55 gr. match bullets out of them but the 1:8 will also shoot well with heavier bullets like 62-69 grain rounds. While the 1:12 twist can only handle rounds 55 gr and lighter. The Rock River Barrels are Wilson Barrel Company barrels. There are many good barrel companies but the Rock River/Wilsons are fine barrels proven by the groups they consistantly produce.
Good luck on your choice!:)


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