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Woodsman
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Here is the article I read showing the averages of five shot groups from 10.3", 11.5", and 14.5" barrels.

https://www.ar15.com/archive/topic.html?b=3&f=118&t=509733
I don't belive this test .....they are getting 3k fps out of a 14.5? I'm pushing the piss out of a 55 grain bullet oUT of a 20" barrel and getting 3100 fps .....yet they are getting close to the same velocity with 5.5" less barrel but say that speeds drastically drop 300fps in 1.5"? Not buying it
 
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1776

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, I'm not saying that 10.3/.5 won't get the job done but velocity is important with 5.56.
Velocity is much less important if you're not restricted to 55 gr. 62 grain is still plenty destructive out of my 10.3" DD barrel. 75-77gr match is more accurate than I can shoot out of it (an acquaintance of mine can can almost break 1MOA and I can get about 1.6MOA on irons/MRO) and the hornady TAP line makes a hell of a wound.
 

boss_hawg

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Believe whatever you want. I saw no reason for the individual who conducted the test to fudge results that they were getting.

Personally, I think that 10" and up barrels are fine. I got the 12" only because it was a really good deal.

Unfortunately, this thread has devolved into a debate on ballistics - exactly where I didn't really want to go (thread derailment). Back to the topic at hand?
 
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1776

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Back on topic: I've been through more than a few muzzle devices of 7.5 and 10.3 barrels.
The KX3 does a good job of redirecting blast, but it adds a bit of length and weight. When I went from a 7.5 with kx3 to a 10.3 with birdcage, I only added about an inch and lost a little over an ounce.
 

boss_hawg

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agreed on the kx3. I would go straight a2 until you decide if and when you get a can
 

fyroc

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20151130_185705.jpg

I'm just needing a riser for the red dot and to see why the damn bolt catch isn't working. It's pretty stiff so the catch or the lower is out of spec.
 

AirOpsMgr

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View attachment 11054

I'm just needing a riser for the red dot and to see why the damn bolt catch isn't working. It's pretty stiff so the catch or the lower is out of spec.
What size riser? I have one sitting in a parts bin you can have if it fits your needs. Will have to dig it up to see what size it is.
 

Willy Leadwell

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Nope. It was a PITA to get it on the lower. It's stuck in the "down" position and the spring can't even push it up.

Sounds like this pin is too tight in the catch. Probably gonna have to drive the pin out and open up the hole in the catch.
 

EugenFJR

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I don't belive this test .....they are getting 3k fps out of a 14.5? I'm pushing the piss out of a 55 grain bullet oUT of a 20" barrel and getting 3100 fps .....yet they are getting close to the same velocity with 5.5" less barrel but say that speeds drastically drop 300fps in 1.5"? Not buying it

That is b/c M855 is NOT loaded to SAAMI specs. Military ammo is around 3000 FPS out of the A2 and just under 3000 FPS out of the 14.5 barrel of the M4.
 

becausefu

Woodsman
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That is b/c M855 is NOT loaded to SAAMI specs. Military ammo is around 3000 FPS out of the A2 and just under 3000 FPS out of the 14.5 barrel of the M4.
How do you only lose around 100 fps in 5.5 inches? I'm just not buying it
 

PewPewPewCo

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How do you only lose around 100 fps in 5.5 inches? I'm just not buying it
Yea I'm feeling the same way here. My 20" is significantly faster than my 16" models and I've played with my elevation enough to know that it's pretty damn different in spees
 

EugenFJR

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I'm just telling what the army TM says, 3100 out of the A2, and 2970 out of the M4... Are you shooting M-855 ball ammo? And I agree, between a 20 bbl, and 14.5 bbl, rifle, I think it would be more, and it very well could be. That being said, I think there would be almost no differance between a 16 inch and 14.5 rifle at the muzzle.
 

boss_hawg

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the relationship between barrel length and velocity is not linear. there is diminishing velocity gains once your get past around 13 or 14" of barrel.

plus, pew - what ammo are shooting?