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"Death From Above"
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Discussion Starter · #1 ·
I was wondering if when I start reloading for my varmatch if there are any benifits in having a gas port that is two inches further down the bore than a standard rifle length gas post location? The barrel is 28 in long 7.7 twist and I planned on using 75 gr SMK BTHP's. In addition, for those of you that have a similar barrel what are some other suggested rounds preferably ones I can continue to use a magazine?
How does the gas port location effect a rifle performance?
 

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Having the port further from the chamber should allow slightly slower buring powder to be used - and that could be an advantage with heavier bullets - e.g. 75+ grain.
This is because the volume of 'barrel space' is slightly larger because of the gas port location, and that would result in a little less gas pressure at the port.

It might also slightly delay bolt opening.

Jay Kosta
Endwell NY USA
 

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"Death From Above"
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Discussion Starter · #3 ·
Thats greatinfomation Jay! Does the same hold true if I were to use a slower powder and a lighter bullet weight? Would the bullet have more velocity?
 

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My 'general understanding' about powder burnrate & bullet weight is -
1) Lighter bullets are easier to accelerate, so a faster burning powder is needed to produce the pressure before the bullet has gone too far down the barrel.
2) Heavier bullets are more difficult to accelerate, so a slower burning powder is still giving increased pressure while the bullet is not too far down the barrel.

I doubt that a light bullet & slow powder would be efficient - most of the powder that is burned would not give much additional pressure or MV.

Jay Kosta
Endwell NY USA
 

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"Death From Above"
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Discussion Starter · #5 ·
Thanks for the input, as you have been able to figure out I am not up on reloading yet. I am sure it is a long process. I am just in the gathering of supplies stage.
 

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If you change your gas port location you will have to make a new gas tube or find a way to safely lengthen your existing one. If your goal is to delay the unlocking of the bolt there are easier ways to do it without having to modify your gas system and barrel. IMO you should work on load development before you think about modifying the rifle. I have built alot of competition AR's for customers over the years and have never felt the need to change the gas system. JMO.
 

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"Death From Above"
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Discussion Starter · #7 ·
Thanks fo rthe input but the barrel is made with the gas port two inches further out than standard rifle lenght from the factory. It is the Krieger Varmatch 28 inch .937 inch barrel.
 
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