Having AR10's in 243win, 260rem and 6.5creed there's been various sized ports. Some are a perfect size regardless of location and some just don't work regardless of location? Most are standard rifle length and some are +2. I'll check sizes and possibly need to open the port up some on the standard length. Here's the question? Who can I send any in question to? Do they need to be someone that smiths AR's or can a general gunsmith do it? This is on an already gas port that has been reamed and barrel has the extension already.
gas port reaming
- Thread starter ARlife4me
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if you have a drill press, vise, and some barrel blocks, you can do this yourself. it helps if you have a set of wire-gauge drill bits and a hole pin gauge set.
from high-school math, do the pi-r-squared thing to determine gas port cross-sectional area, and take a guess at how much percentage increase you want to open it up by, based on the nature of the undergassed symptoms from shooting a selection of your usual ammo.
my experience has been that this is an iterative process, because you don't want to go too big at the outset, you want to sort of creep up on the "just right" gas port size. I've used 10% to 15% gas flow CSA as a starting point, depending on type of symptom.
a 10% increase in drill bit diameter results in 21% increase in CSA. it increases as a squared factor.
a better gunsmith will give you a gas port that doesn't have a bunch of dingleberries hanging in the rifle bore.
from high-school math, do the pi-r-squared thing to determine gas port cross-sectional area, and take a guess at how much percentage increase you want to open it up by, based on the nature of the undergassed symptoms from shooting a selection of your usual ammo.
my experience has been that this is an iterative process, because you don't want to go too big at the outset, you want to sort of creep up on the "just right" gas port size. I've used 10% to 15% gas flow CSA as a starting point, depending on type of symptom.
a 10% increase in drill bit diameter results in 21% increase in CSA. it increases as a squared factor.
a better gunsmith will give you a gas port that doesn't have a bunch of dingleberries hanging in the rifle bore.
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dennisinaz
Well-Known Member
The dingleberries are gone after the first shot
unfortunately, sometimes the first round drags the steel dingleberry along and carves out some nice gouges. you can see it with the bore scope, gouges or drag marks that originate at the gas port. depth of scratch determined by how big the dingleberry was.
but in the grand scheme of things, perhaps it doesn't matter, after all, lots of folks say that you don't want to look at a bore scope because it doesn't show you anything good, even on a fine-shooting barrel.
but in the grand scheme of things, perhaps it doesn't matter, after all, lots of folks say that you don't want to look at a bore scope because it doesn't show you anything good, even on a fine-shooting barrel.
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IF, I were to do it myself I do have a set of pin gauges and a fine set of bits. I would/could ream/drill out a larger diameter a little at a time as to lessen the amount of shavings? Bit cutting angle (115*, 135*, etc) for best choices or whatever someone else could suggest? HSS bits or some other choice for possibilities?
dennisinaz
Well-Known Member
I just drove a lead slug into the spot where i need to drill. It pretty much eliminated the typical swarf that a fool creates
i bought the necessary bits to open one up one time and then it turned out I didn't have to. If you go a little too large you can always go with a heavier spring or buffer or tone it back down with an adjustable gas block. As for dingleberries you could lap it lightly afterwards or use bore paste to tone thone down a bit.
I have opened up ports on under gassed shotguns before With good effect. Mostly 20 gauges. Go slow and use a good cutting oil. Step up just a very small amount at the time. Let the bit do the work.
I have opened up ports on under gassed shotguns before With good effect. Mostly 20 gauges. Go slow and use a good cutting oil. Step up just a very small amount at the time. Let the bit do the work.
TonyRumore
Well-Known Member
Use a Cogsdill Burr-off tool to debur the inside of the hole.
Tony Rumore
Tromix
Tony Rumore
Tromix
