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Old 01-28-2018, 06:56 PM   #1
Bluntforce
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Question 14.5 inch AR barell reliabilty

I have heard a lot about 14.5 inch AR barells with carbine length gas systems being unreliable. I have never found an explanation why or any remedy. Mid-length gas system is not as unreliable but doesn’t seem to be as common on the market.

Is there anything that can be done to increase reliabilty, i.e. different weight of BCG, buffer weight or spring strength? Does bullet weight have any part in this equation?
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Old 01-28-2018, 09:46 PM   #2
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14-1/2" should be just as reliable as the length of barrel past the gas port is the same as it is on a rifle length 20" or a mid length 16", meaning the dwell time of the gas impulse is the same.
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Old 01-28-2018, 09:54 PM   #3
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Old 01-28-2018, 10:41 PM   #4
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Quote:
Originally Posted by Bluntforce View Post

Is there anything that can be done to increase reliabilty, i.e. different weight of BCG, buffer weight or spring strength? Does bullet weight have any part in this equation?
I have fired many thousands of rounds of 5.56 through 14.5 inch barrels and carbine gas systems, with bullets of the following weights: 50, 55, 62, 69, 77 grains.

In rifles of top quality manufacture (Daniel Defense, Noveske, Colt, or similar) I have had no problems.

However, many people experience trouble with the more economically priced rifles (CMMG, DPMS, Rock River, etc.). This is because they lower the price by sacrificing product quality.

You can replace the LPK, buffer tube, buffer spring, recoil buffer and BCG with proper M4 milspec parts. Then assuming that your barrel port and gas tube line up correctly, the gun should run great. Or you can sell the budged AR15 and fork out a bit more money for one of the premium guns.

This article has some info on quality parts vs. budget parts:

http://www.thenewrifleman.com/the-ar...a-great-rifle/

It is true that the carbine gas system has higher peak gas pressure and supposedly slams the action harder. Maybe over 50,000 rounds that will matter. I have not found that it matters with over 10,000 rounds per gun, if the gun is constructed using milspec or better parts.

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The chamber pressure on a carbine gas system and a 16″ barrel can average around 25,000psi while a rifle gas system on an 18″ barrel can average around only 17,000psi, a reduction of over 30% in pressure. All of that extra pressure can stress the parts of your BCG and cause premature bolt failures, among other problems.
http://apdmarksmanshipteam.org/blog/...15-gas-system/
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Old 01-29-2018, 12:35 AM   #5
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Thanks, I know somebody wanting to build a shorty. I’m trying to talk them into at least a 16” because it’s such a velocity sensitive round and you have to pin the flash hider on immediately or get locked up. I wouldn’t build anything shorter or longer than 20”. If I wear out my carbine length barrel I’m replacing it with a rifle length barrel.
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Old 01-29-2018, 12:46 AM   #6
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I have a colt 14.5" socom barrel that would not cycle reliably with 55 gr ammo...i had to remove the front sight block and drill the gas impingement hole slightly larger....it now works very well.

I have had this same issue on several AR's of all different barrel lengths though.
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Old 01-29-2018, 04:05 AM   #7
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Geez I have a little SBR Rock River with an 8 in. "I think short of measuring" chrome lined barrel and that thing is deadly accurate at a 100 yds.
Put a $79 Bushnell red dot sight on it and it works just fine for my old eyes. Now accurate for me is hitting a squirrel at a 100 yds. not taking out the poor things eye. Long range shooting in Fla. is 100 yds. anything past that we have to watch the sportsman's channel on T.V..
Reliability? Boxes and boxes of mix and match ammo me shooting my buddy shooting and never ever a FTF or eject.
I visit buz and you guys out west I would love to do some long range stuff.
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Old 01-30-2018, 01:58 AM   #8
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Quote:
Originally Posted by 4thIDvet View Post
Long range shooting in Fla. is 100 yds. anything past that we have to watch the sportsman's channel on T.V.
Hey 4th. There used to be a 600yd range at MacDill and a 1000yd range on the north end of the Big Lake. I can't find the info on them right now but I do know there is a newer range right outside Okeechobee that goes to 200.
Mayakka, a little SW of StPete has 25, 100, 200, 300, and 600yards. Mayakka also hosts the Appleseed events.
If you can get to a 5-600 yd range, you'll be surprised just what these little varmint rifles can do. I must admit though, I cheat. A-1 butt stock, A-3 handle and a 24" barrel with a 5" compensator. Longest AR I've ever seen.
REACH OUT AND TOUCH SOMEONE

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Old 01-30-2018, 04:19 AM   #9
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Hey 4th. There used to be a 600yd range at MacDill and a 1000yd range on the north end of the Big Lake. I can't find the info on them right now but I do know there is a newer range right outside Okeechobee that goes to 200.
Mayakka, a little SW of StPete has 25, 100, 200, 300, and 600yards. Mayakka also hosts the Appleseed events.
If you can get to a 5-600 yd range, you'll be surprised just what these little varmint rifles can do. I must admit though, I cheat. A-1 butt stock, A-3 handle and a 24" barrel with a 5" compensator. Longest AR I've ever seen.
REACH OUT AND TOUCH SOMEONE

cerberus
Oh long range shooting is available here cerberus. East of here a bit is a 1,000 yard range one of our members? asked me to come out to.
I called and they want me to take a course in long range shooting and qualify before I can use it? Now reading and understanding the rules I can understand but I am to old for Green Beret school just to shoot at the damn range.
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Old 01-30-2018, 09:27 AM   #10
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Do some research on adjustable gas blocks. I plan to use one on my next build. Be able to fine tune your rifle/pistol for any length barrel or ammo.
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Old 01-30-2018, 11:02 AM   #11
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Do some research on adjustable gas blocks. I plan to use one on my next build. Be able to fine tune your rifle/pistol for any length barrel or ammo.
FALs come with that already installed. Plus, they make a BIGGER HOLE
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Old 01-30-2018, 07:02 PM   #12
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Quote:
Originally Posted by Bluntforce View Post
Thanks, I know somebody wanting to build a shorty. I’m trying to talk them into at least a 16”
14.5" with a mid length gas tube seems to work quite well if premium parts are used.

https://danieldefense.com/firearms/d...eep-woods.html
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Old 01-30-2018, 11:04 PM   #13
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The weight of the buffer is what you need to watch. Sometimes enlarging the gas port is a ligit fix.
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