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Seemed bore fluctuation at gas port


JaredBT

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Hello all Im breaking in a barrel, Im feeling what seems like a fluctuation in the rifling / bore diameter at the gas port hole area of my 308 20" bore... While running a patch down the bore, when I get to the gas port the pressure (resistance pushing the rod) lessens at the port area then picks up again just past it. Visually I cant see anything wierd. Any thoughts?
 

Thanks.

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Interesting.  I have the same sort of bore variation with a Ruger MKIII pistol.  Cleaning from the breach end, there is an area about 7/8" long ending at the muzzle that is noticeably "looser" than the preceeding bore.

My theory is that this particular barrel was clamped super-mongo hard when being bored and then, when the clamping force was loosened, it allowed some spring force in the steel to open up a couple of thousandths or so of an inch.  I've seen this happen with non-barrel lathe work.

That being said, what type brand of rifle is this we're talking about?  Did you purchase/acquire this rifle new?  Is the outside of the barrel bulged?

I've seen .30-30 rifles and handguns "ring" the barrel, when they were fired with a barrel obstruction, the ring appearing just behind where there obstruction had been.

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8 hours ago, JaredBT said:

Hello all Im breaking in a barrel, Im feeling what seems like a fluctuation in the rifling / bore diameter at the gas port hole area of my 308 20" bore... While running a patch down the bore, when I get to the gas port the pressure (resistance pushing the rod) lessens at the port area then picks up again just past it. Visually I cant see anything wierd. Any thoughts?
 

Thanks.

Contact the Barrel / Rifle manufacturer , If possible , if not , have it checked by ADCO or some other Barrel maker/repair or replace the barrel . Hard to say whats up , but the explanations above sound possible . 

Edited by survivalshop
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