Barrel Length vs. Gas System Options
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Barrel Length vs. Gas System Options


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Old 01-15-2011, 05:48 AM   #1
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Default Barrel Length vs. Gas System Options

So, this really wouldn't have worked as a poll, nor did I want it to be one. I've really been enjoying this section lately as there's been some good content backed up by experience.

To the Topic:

On a Practical Level. . .

How do YOU determine what length gas system YOU will use on your (X") barreled upper? Why?

I know the basic "Normal" or "ideal" set ups that all have close to the same dwell time:

14.5" = carbine length
16" = mid length
20" = rifle length

OK, that's a good gauge, but I kinda like the way my 14.5" middy shoots. What about an 18" barrel? Mid or rifle?

Let's hear it!
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Old 01-15-2011, 02:21 PM   #2
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As you said midlength works very well for 14.5 to 16". There is some overlap since you can adjust timing, dwell and pulse intensity with many factors such as gas port size, position and bolt carrier/buffer reciprocating mass. Each manufacturer does it different and you can change some of the factors yourself.

KAC has an intermediate length gas system that works well for 18" or even 16". Rifle does well on 18" too. Mid might work but I'd go with a longer gas system.

Last edited by Quentin; 01-15-2011 at 02:24 PM.
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Old 01-15-2011, 04:08 PM   #3
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I cant really add anything to what Quentin said. In my eyes 14.5" midlength is ideal.
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Old 01-15-2011, 05:11 PM   #4
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I agree with mjkeat that a 14.5" midlength is ideal. But in the real world with legalities and for flexibility I went with a 16" midlength for my first build and did it again with my second (but this time with a lightweight barrel profile). I just don't want a pinned/welded muzzle device and when it comes down to it the actual differnece in length is barely an inch.
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Old 01-15-2011, 06:27 PM   #5
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MJ and Q got it. The mid-length and full length have a smoother recoil impulse.
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Old 01-15-2011, 09:15 PM   #6
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Well I guess if 14.5" mid-length is ideal, which I can't argue with after shooting my mid-length BCM upper today. I couldn't imagine anything smoother.

Then that would mean that rifle length would be sweetest for an 18" barreled upper. . . ?

I'll post up a target from 200 yds that the BCM put out using Silver Bear ammo in range reports.
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Old 01-15-2011, 09:42 PM   #7
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Quote:
Originally Posted by diggsbakes View Post
Then that would mean that rifle length would be sweetest for an 18" barreled upper. . . ?
yup you got it.
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Old 01-16-2011, 12:11 AM   #8
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Id like to try a 16"-16.5" w/ rifle length gas system out of curiosity.
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Old 01-16-2011, 01:17 AM   #9
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Quote:
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yup you got it.
Yeah that was truly rocket science. . . Does anyone have experience with an 18" barrel/rifle length AR set up?
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Old 01-16-2011, 01:19 AM   #10
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That would be nice MJ. Or intermediate length but then there's so little selection for furniture/rails. Yeah rifle...

ETA... didn't see your post Diggs... no 18" here.

Last edited by Quentin; 01-16-2011 at 01:22 AM.
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