AR15 gas port burr removal?

[Vettepilot]

Hey guys,

What's the best way to remove this burr on the gas port of my barrel? I'm just assembling the gun, and would rather remove it than shoot it out with j boolits.

Thanks,
Vettepilot

[popper]

Just shoot it out with thick wall jacketed. They put it in the wrong place! Should be top of the land.

[Gtek]

I always worry they will get in BCG and scar things up. Adjustable gas I close for the first 5-10 jacketed rounds, I have pushed a really tight #0000 wool on jag and got them. Oh those bore scopes, never had a lot of problems till I bought one of those!

[cwtebay]

Try torch tip files.

Sent from my Pixel 3 XL using Tapatalk

[M-Tecs]

I have a diamond dental burr bit with a ball small enough that I can reach in the .093" hole. I turned it by hand. Did a couple that way. Same for hand lapping. Did a couple and gave up. Shot a lot out and never saw any evidence that shooting the burr out was an issue.

I've install a lot of Krieger's and they generally don't have a burr. If I am drilling the gas hole myself I drill undersize and use a .093 or a .096" carbide endmill. That doesn't leave a burr.

Krieger started the drill on the groove BS as a marketing issue. John regrets doing that since they have had to eat a lot of barrels that they missed on. Reality is covered here in post #9

http://benchrest.com/showthread.php?...-gas-Port-AR15

I have inspected the port (with a borescope) on every AR barrel that we have built up in the past couple years, and have inspected the ports again on a number of these barrels after they later came back for a rebarreling after being shot out, and by far the barrels showing the most disruption and deformation of the barrel metal forward of the port inside the bore (i.e. it's always all on the muzzle side of the port) are those where the port is in the groove. The ones that show the least amount (in many cases next to no disruption or deformation of barrel metal) are where the port bisected the land and groove.

When I inspect the barrels where the port is in the groove I typically see a very significant area forward of the gas port (toward the muzzle) where the barrel metal has been repeatedly slammed with bullet jacket, so much so that this rips, tears, wears and deforms a large triangular shaped portion of the bore forward of the port. Many times you can see hunks of torn off copper bullet jacket embedded into this area. Plain and simple, I just don't see this situation so much where the port is in some other locations in the bore and the best looking bores and ports appear to be where the port bisects the groove and a land (i.e. half into a land and half into a groove).

What I see indicates (to me) that bullets are still flexible and plastic even when they pass the gas port. It seems there's still enough pressure in the bore and plasticity in the bullet that it will start to squeeze into an "in the groove" port as it goes by it, and that squeezed in portion of the bullet then slams in to the other side of the port on the muzzle side and either a bit of jacket gets torn off or that portion of the bullet gets swaged back fully into the bore again (or a little of both).

There is consistently less copper seen and evidence of barrel disruption with the 50/50 ports or those that are half in the land and half in the groove (keep in mind the bullet jacket, after engraving into the lands, has adopted a shape with two almost right angles at the location where it is going to go over the 50/50 port and it seems those angles add rigidity to the bullet so that the jacket does not seem as predisposed to squeeze into the port). For an example, angle iron is a lot stiffer than flat iron and so is that portion of the bullet with two right angles in the jacket.

The "in the groove" port is like a big pothole sitting right in the middle of where your car tire will center up and hit it square and hard at high speed and it makes a situation you sometimes see on an asphalt road that started out like a small hole or depression in the road where cars and trucks at high speed keep slamming into it busting it up further along as they keep hitting it and deforming the asphalt a bit beyond that.

The irony of this whole thing is, when we first started building uppers we tried as best we could to hit the groove with ports and I used to have fits when I saw ports half in and half out of the groove, worrying about if a customer would have a fit about that as well. Now I have gone full circle and hope I hit the junction of the land and groove.

Robert Whitley
www.6mmAR.com

[Vettepilot]

Thanks for the ideas so far guys.

Yeah, when I first saw exactly where the port was, I was pleased.

Vettepilot

[Moleman-]

That's really not much of a burr. When drilling the gas port I'll go slightly smaller than the port and then drill it so any burr is thin. Take a couple shots and then wipe out the inside of the bolt carrier and the bolt tail in case anything made it in there. I have had a chunk of bur end up in the BCG and chew up a set of gas rings. The bolt and BCG are harder than the barrel steel.

[popper]

It's gas cutting, just like a shot out throat. Muzzle end of hole sees high pressure gas and erodes. Gas cutting, just like leading occurs at the edge of the land. Hole in the top of the land has least leading and possibility of gas cutting. But it will take a LOT of shooting to be a problem. Such a small burr will disappear after just a few rnds. Don't sweat it, just shoot it.

[country gent]

I sectioned several m1A barrels at the chamber throat and gas port when shot out. It was amazing how far forward in the throat the erosion went. But even more was the radius burned on the gas port hole from erosion. Between the bullet passing and the erosion that fine burr wont last long. A jag and tight patch will probably peel most off. those burrs arnt held in by much. I also drill small and then ream to size with the right size drill. I also turn the finish rill by hand. so burrs are very small and thin.

[akajun]

I have a diamond dental burr bit with a ball small enough that I can reach in the .093" hole. I turned it by hand. Did a couple that way. Same for hand lapping. Did a couple and gave up. Shot a lot out and never saw any evidence that shooting the burr out was an issue.

I've install a lot of Krieger's and they generally don't have a burr. If I am drilling the gas hole myself I drill undersize and use a .093 or a .096" carbide endmill. That doesn't leave a burr.

Krieger started the drill on the groove BS as a marketing issue. John regrets doing that since they have had to eat a lot of barrels that they missed on. Reality is covered here in post #9

http://benchrest.com/showthread.php?...-gas-Port-AR15

I have inspected the port (with a borescope) on every AR barrel that we have built up in the past couple years, and have inspected the ports again on a number of these barrels after they later came back for a rebarreling after being shot out, and by far the barrels showing the most disruption and deformation of the barrel metal forward of the port inside the bore (i.e. it's always all on the muzzle side of the port) are those where the port is in the groove. The ones that show the least amount (in many cases next to no disruption or deformation of barrel metal) are where the port bisected the land and groove.

When I inspect the barrels where the port is in the groove I typically see a very significant area forward of the gas port (toward the muzzle) where the barrel metal has been repeatedly slammed with bullet jacket, so much so that this rips, tears, wears and deforms a large triangular shaped portion of the bore forward of the port. Many times you can see hunks of torn off copper bullet jacket embedded into this area. Plain and simple, I just don't see this situation so much where the port is in some other locations in the bore and the best looking bores and ports appear to be where the port bisects the groove and a land (i.e. half into a land and half into a groove).

What I see indicates (to me) that bullets are still flexible and plastic even when they pass the gas port. It seems there's still enough pressure in the bore and plasticity in the bullet that it will start to squeeze into an "in the groove" port as it goes by it, and that squeezed in portion of the bullet then slams in to the other side of the port on the muzzle side and either a bit of jacket gets torn off or that portion of the bullet gets swaged back fully into the bore again (or a little of both).

There is consistently less copper seen and evidence of barrel disruption with the 50/50 ports or those that are half in the land and half in the groove (keep in mind the bullet jacket, after engraving into the lands, has adopted a shape with two almost right angles at the location where it is going to go over the 50/50 port and it seems those angles add rigidity to the bullet so that the jacket does not seem as predisposed to squeeze into the port). For an example, angle iron is a lot stiffer than flat iron and so is that portion of the bullet with two right angles in the jacket.

The "in the groove" port is like a big pothole sitting right in the middle of where your car tire will center up and hit it square and hard at high speed and it makes a situation you sometimes see on an asphalt road that started out like a small hole or depression in the road where cars and trucks at high speed keep slamming into it busting it up further along as they keep hitting it and deforming the asphalt a bit beyond that.

The irony of this whole thing is, when we first started building uppers we tried as best we could to hit the groove with ports and I used to have fits when I saw ports half in and half out of the groove, worrying about if a customer would have a fit about that as well. Now I have gone full circle and hope I hit the junction of the land and groove.

Robert Whitley
www.6mmAR.com

This is money in the bank right here, the Krieger i legged out with and made high master had the port in the groove, and had a comet tail from the gas port about 1” long. That barrel still shot hm scores at 600 when I did my part till 5K rds. When I started doing my own work I did a few trying to hit the groove and what a pain in the butt. When people I respect started telling me I was wasting my time I just started drilling them randomly and your right, the split holes do not end up with a comet tail and all shoot very well.
As far as burr removal , if your really worried about it a patch with jb bore paste will get it out, but I’d just shoot it with normal jacketed ammo. Next time you drill, drill undersize and use a reamer to finish the hole.

[LynC2]

Many years ago when I started building AR match rifles I asked Bill Wylde (well known AR gunsmith) about locating and drilling the gasport without getting a burr. He replied he drove a lubricated bullet under the gas port location before drilling, but didn't see any difference in accuracy regardless of it being in the groove or at random. Later on when I drilled a gas port I also drilled undersize and reamed to size. After a couple thousand rounds that nice round hole looks like a pig waller anyway.

[Vettepilot]

An update:

Well, I always supposed that being a bit "OCD" and a perfectionist was a "good thing" when it came to my guns and reloading...

So, a quick update. Especially being that it is a new build, I just didn't want to "shoot that little burr out". So, while doing the normal new barrel clean, I went after that burr. I took some real, live, honest, (and hard to find!!) COPPER Chore Boy, wrapped it around an undersize brush, and had at it like you would for stripping out lead deposits. That and some brushing with a fairly tight brass bore brush, and I figured it was a done deal. Well, that took most of it out, but there was still a fair sized chunk left. I just didn't want that stripping copper off the first rounds down the barrel, and as tough as it was, it surely would. Finally, I took my cleaning rod, and with the help of my bore scope, finally knocked that last piece off. Then I flushed and cleaned the gas port and the barrel again, and it's all back together, ready for the maiden range trip. I'm glad I did it, even though it took a good while and was tedious. But better that than the burr coppering up my barrel during break in, and/or worse, a piece of burr making it back to the BCG!

Thanks for the responses,
Vettepilot

[Vettepilot]

I helped my brother throw together a new AR a while back. It was at his home, 350 miles from mine, and I didn't have my bore scope with me. When we did the "new barrel cleaning", it took forever to get all the copper out. I'm thinking that his probably had the same problem as the one I've discussed here, and the factory test shots caused a bunch of copper deposits.

Vettepilot

[Lloyd Smale]

nothing a thousand rounds of mag dumps wont take care of!

[Wolverine19D]

I understand being OCD about it but for me there just isn't any reason not to shoot it out. I would not waste my time trying to get something like a small burr out when a couple rounds down range would work the same. If you're worried about the BCG take it apart after each round starting out. I imagine the chances of that happening are about none since 99.9% of new barrels out there likely have burrs and are shot out by most shooters. That said, I'm sure it does happen but not something that would worry me.

[swheeler]

Our first AR had a burr there, Anderson M15 OR, would catch a patch when brand new right at port, I think it disappeared after the first 2 mags full of jacketed ammo. That gun never did shoot very accurate, but the one that replaced it is very near MOA with ammo left over from first gun. I have never bore scoped either, but melonited barrel is as smooth as can be, very little copper.

[Vettepilot]

Well, we've all heard of barrels being damaged/ruined by improper cleaning. My thought is, if an aluminum cleaning rod can cause bore damage just by touching the bore during cleaning, a fair size steel burr leaving the bore by being trapped between a projectile and the bore just can't be a "good" thing. I very well might be over thinking it. Wouldn't be the first time I've done that. But yielding to your OCD tendencies does tend to let you sleep better. .

Vettepilot

[swheeler]

OCD can be a beach!

[Vettepilot]

Sometimes a "gift", (saved my life a time or two as a pilot), and yes, sometimes a "Beach"!! (Especially to those around you whom are NOT that way.)



Vettepilot

[M-Tecs]

Well, we've all heard of barrels being damaged/ruined by improper cleaning. My thought is, if an aluminum cleaning rod can cause bore damage just by touching the bore during cleaning, a fair size steel burr leaving the bore by being trapped between a projectile and the bore just can't be a "good" thing. I very well might be over thinking it. Wouldn't be the first time I've done that. But yielding to your OCD tendencies does tend to let you sleep better. .

Vettepilot

Aluminum is surprisingly abrasive. Most aluminum rods are jointed and flexible enough that even with a proper bore guide they can rub on the bore. If it is done a lot in the same place you are in effect lapping that area. I do have a couple of joined aluminum rods for emergency field use. Other than that they will need see the inside of a rifle bore.