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Dwell Time


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This is the very MAIN factor in determining gas port size - how much barrel do you have, AFTER the gas port?  Other important factors are gas length system, gas block journal size, caliber, and proper recoil system - in that order, exactly in that order.  If you don't balance the recoil system and that gas system - you are fukked.  They are both equally important, for a "functioning rifle."

Glad to see Brownell's step up and make a video on this.  They nailed it on this video.

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9 minutes ago, sketch said:

Your going to put yourself out of business by teaching us. I really like it when you have to repeat yourself. good vid👍🍻

I want everyone to be smart about these things, and what makes them run right.  Everyone.  Been preaching about proper "dwell time" for years - and now Brownell's has a video about it...   I commend them, and they got it right...   :hail::thumbup:

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23 hours ago, unforgiven said:

So on this 16" mid gas Aero how close to the gas block can I go? I'll cut back on the handguard as 12" is shortest made.

How close to the gas block can you go to do what?    The uninformed about upcoming project want to know!   :thumbup:

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2 hours ago, unforgiven said:

I don't want to fuk this up so I need more information also will shorting the barrel change gas port diameter? Like I said it runs@16"

Are you gonna get this 16" midlength, and cut it down?  You asking how far you can cut it down?   13.5" of barrel is about as far as you can go.  You could make 12.5" work, with midlength gas, I have one, but you can't pin a 12.5 and make it legal.  You can pin a 13.5 and get it legal.

 

Shortening the barrel WILL DEFINITELY need a gas port diameter change.

Edited by 98Z5V
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What would be the benefit of something like that?  If you’re going to reach 16”, why not have more barrel than flash hider?  I would have to imagine the weight would be similar.  Lower velocity a goal?  Just curious…not trying to poke. 

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I am probably going to add a longer muzzle break to one of my 308 pistols and turn it into a rifle.

Just don't see the need (I know need has nothing to do with it)
for 2 308 pistols.

If the brace thing gets stupid I might have to do a few more pistols that way.

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7 hours ago, dpete said:

Those are gonna be 1/2 x 28, and 5.56 holes in them.  Threading onto a .308 barrel will be hard, and the first round will be exciting...  :banana:

 

1 hour ago, unforgiven said:

I have a pistol lower for this modification. I'm ok with 13.5" what does that do to gas Port diameter? Lower has KAK 2.5" heavy buffer and orange springco.

Does that really matter, where you are?  Pistols can always turn into rifles, but rifles can never turn into pistols.  So says the federal law.  I'll find the gas port data from my 13.5" Armalite build.

EDIT - Rene, 13.7" barrel will be better, because any company's "extended muzzle device" will reach 16".  On the Armalite 13.5" barrel that I have, I used their own 4-port brake, which goes 16.10"...

Also, if you're building a pistol - only a pistol - barrel length won't matter much.  Well, unless these assheads go through with all this pistol-brace shiit.  At that point, make sure your gun is over 26" total.  OAL.

Edited by 98Z5V
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@unforgiven, Rene, I pulled this out of the build thread. 

Measured the gas port - 13.5" barrel, midlength-ish gas system, using a port size of 0.081".    We'll see how she runs. 

It's actually the Armalite AR-10 Carbine gas system, on their barrel.  Gas port info will be the same, if you cut to 13.5" or 13.7".  It's from this build thread:

 

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Lots of comps/ forwarders/ linear comps on ebay 3.25" to 4.5" search 5/8x24 

Aluminum is nice for weight but welding the pin takes some thought. 

Used .079 on two 12.5" builds, .75 journal, first one would be similar dwell to a 13.5 as the sig gas port was about 1" further down the barrel then it should be. Second one re-drilled to correct location. Both run great. 

Just a thought, maybe we should start tracking gas tube length on the port diameter thread

Edited by Albroswift
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27 minutes ago, Albroswift said:

Just a thought, maybe we should start tracking gas tube length on the port diameter thread

I think we have been - if people were inputting their barrel dimensions correctly.  If they weren't, their info was garbage in-garbage out.

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