gas port erosion pics, new and after 100 rounds.

vincent7

vincent7

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Jan 14, 2019
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#1
Stainless 18" rifle length 223/ 556, 100 rounds, slow fired, mixture between factory and reloads. Black hole weaponry barrel.

One pic before installed and fired ( might have been test fired at factory once or twice, since there was some black crud in there.

Second pic after 100 rounds.

Pic of throat after 100 rounds, didn't make a pic when new.

Throat still looks about the same. Surprised how fast the gasses start chipping away at the gas port hole.

Barrel shoots really well, hope it lasts for a while :)


PICT0008.JPG
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#3
Nice shep whatsupdoc! :)

Nah, not losing sleep over it, just surprised.

Also have a cheapo carbon steel barrel with 5 times as many rounds through it, and there the erosion is about half of what i see in this stainless one, with similar type rounds being fed and shot at about the same rate (slow). We'll see where this goes..
 
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#4
vincent7 said:
Nice shep whatsupdoc! :)

Nah, not losing sleep over it, just surprised.

Also have a cheapo carbon steel barrel with 5 times as many rounds through it, and there the erosion is about half of what i see in this stainless one, with similar type rounds being fed and shot at about the same rate (slow). We'll see where this goes..
Click to expand...

Keep an eye on it of course, but - erosion happens the fastest right at first when those edges are sharp. It should slow down now that it's rounded off a bit. This is the same principle whether we're talking about gas ports or just using a cutting torch on steel plate.

It'd be interesting to see another comparison pic at 500 or 1,000 rounds. I use a handful of BHW barrels too and haven't noticed any changes to gas flow in the system or accuracy dropping off, but haven't put a bore scope down them either. They certainly do shoot well.
 
#6
First pic shows why stainless barrels need to be broken in before best accuracy will be found. Those edges pushed into the bore when drilling the gas port will remove copper from the bullets until they are smoothed out.
 
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#10
Factory loads used were some of those red 100 rounds federal 55 grain 223 packs from walmart ( this batch of brass absolutely sucks, off center flash holes, inconsistent bullet weight and size) and norma tac 55 grain 223 rem black box ( wonderful reloading brass) Probably about 50 or so in total.

Rest were reloads, pretty much all ramshot tac, h335, and cfe 223, from 55 to 69 grain, all loaded within 223 rem specs.

Shoots great, but curious to see how long that holds up as well:)
 
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#13
Ballistic Advantage barrel. Note that the gas port cuts into a land and there is a huge burr.

ballistic_advantage_gas_port_burr_07b_re-1299287.jpg




Larue barrel. Little to no burr, but the gas port cuts into a land.

predatar_barrel_gas_port_01b_resized-1299280.jpg




Krieger barrel. Krieger Barrels Inc. drills the gas port in the dead center of a groove so that the gas port doesn't encroach on the lands and of course there is nothing in the way of a burr.

krieger_gas_port_unfired_03_resized-1299285.jpg




....
 
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#14
The shorter the gas system, the more rapid the erosion. The bore-scope view below shows the gas port of a 14.5" chrome-lined CMV AR-15 barrel with a carbine length gas system after only 500 rounds have been fired from it.



gas_port_02_resized-1299315.jpg




....
 
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#15
rth1800 said:
How does it shoot is only part of the question. The other is how long is it going to shoot that way. Premature wear or erosion can be an issue.
Click to expand...
My larger point was that you can drive yourself crazy using a borescope to diagnose problems that don't exist. If it shoots well, put the bore scope somewhere you'll lose it and shoot the rifle.
 
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#17
I've got one gas port in a SS match bbl that is eroded so bad you can't get it all in 2 pics, you'd need to show a movie. I'd estimate 5/8" or a little more not counting the port.
A 243 WSSM with about 900 rounds on it.
Still shoots under 1/2 MOA 5 shot groups.
 
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#18
I had a Krieger that was run hard and eventually died at 3200 rounds. At around 2500 I had it borescoped @bohem and it looked terrible. Tail behind gas port longer than the port itself. It had not lost accuracy at that point yet. It did lose velocity though.
 
#19
Constructor said:
First pic shows why stainless barrels need to be broken in before best accuracy will be found. Those edges pushed into the bore when drilling the gas port will remove copper from the bullets until they are smoothed out.
Click to expand...

Pretty much true. Chrome Moly 4150 type steel is actually more accurate, but most opt for 416R stainless as 4150 requires some constant lubrication to prevent rust. I am not familiar with the name of the barrel, and while others note to watch and see, I am a bit surprised to see that level of gas port erosion at 100 rounds.

Another point of interest. 18" rifle barrels are known for very fast gas port erosion, and are generally not recommended to precision shooting. the pressure difference at 18" is much greater than at 20" on a rifle system. I have seen many good brands erode beyond use after 5,000 rounds. The one exception, in my experience, is Douglas. I am not sure why. May their stainless is a bit harder than others.
 
#20
Am now at 150 rounds, scoped it again. Looks about the same, so the gas port wear seems to slow down.
Made some pics and will keep doing this for every 50 or 100 rounds, so i can keep tack.
Will share pics again when erosion seems to advance further down the bore. Shoots darn nice right now (sub MOA with handloads) .
Paid only $125 plus $20 or so for shipping for the barrel, so i'm happy :)

At 150;
150..JPG
 
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#21
longshot2000 said:
Pretty much true. Chrome Moly 4150 type steel is actually more accurate, but most opt for 416R stainless as 4150 requires some constant lubrication to prevent rust. I am not familiar with the name of the barrel, and while others note to watch and see, I am a bit surprised to see that level of gas port erosion at 100 rounds.

Another point of interest. 18" rifle barrels are known for very fast gas port erosion, and are generally not recommended to precision shooting. the pressure difference at 18" is much greater than at 20" on a rifle system. I have seen many good brands erode beyond use after 5,000 rounds. The one exception, in my experience, is Douglas. I am not sure why. May their stainless is a bit harder than others.
Click to expand...
The gas port on a 18" RLGS is located in the same spot as a 20" RLGS so the pressure at the port is the same. We port the 18" and 20" barrels .093"
As for 4150 rusting, very few make untreated barrels unless it is a small smith/home operation. We have been Melonite/Nitride treating barrels since 2008 , they last longer and have better corrosion resistance than stainless.
 
#22
Constructor;
Temperature, pressure and maybe dwell time might all contribute to port erosion.
Right?
I'm thinking torch for a longer period, more gas through the port?
Maybe compare a 18", 20" 22", 24" with rifle gas?

Also :)
If it's not picking up copper will if impact accuracy?
That's a pretty small section compared to the entire bore.
 
#24
Rocketvapor said:
Constructor;
Temperature, pressure and maybe dwell time might all contribute to port erosion.
Right?
I'm thinking torch for a longer period, more gas through the port?
Maybe compare a 18", 20" 22", 24" with rifle gas?

Also :)
If it's not picking up copper will if impact accuracy?
That's a pretty small section compared to the entire bore.
Click to expand...
A 20 or 24 has more dwell time so if the ports are the same size they should erode faster but if the 18" is ported larger then the 18" would have more flow and possibly erode faster.
You are right, it is a small area and if the material isn't protruding into the bore it shouldn't drag copper off the bullet and effect accuracy. Stainless is so soft compared to melonite treated 4150. The material when the bit is half way though gets so thin that the bit pushes the material forward to the outside edge of the port and into the bore instead of cutting it. On a melonite treated barrel that thin area is like a crust and stays in place until the bit cuts it.
I'm approaching 60,000 barrels and I scope every one. I sell stainless because some people want them but if it was up to me I wouldn't sell stainless since the melonite treated barrels last longer and are really more corrosion resistant. In order to drill a port without flow in a stainless barrel the first bit needs to be a .062 then stepped up twice with reamers...very small reamers that break easily. Most companies just drill them out with a drill bit and it takes 50-200 rounds to wear that area away that protrudes into the bore.
 
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#26
The problem with melonite barrels is the extra cost of having a single, or two done.
Especially if it's not a normally stocked configuration.
Buying one from someone that does exactly what you want in larger lots is hard to find.

Start with a $300 barrel (yup, I'm cheap) what is the add on to have it treated?
 
#27
Rocketvapor said:
The problem with melonite barrels is the extra cost of having a single, or two done.
Especially if it's not a normally stocked configuration.
Buying one from someone that does exactly what you want in larger lots is hard to find.

Start with a $300 barrel (yup, I'm cheap) what is the add on to have it treated?
Click to expand...
You should see if @Constructor stocks what you're looking for...
 
#28
Rocketvapor said:
The problem with melonite barrels is the extra cost of having a single, or two done.
Especially if it's not a normally stocked configuration.
Buying one from someone that does exactly what you want in larger lots is hard to find.

Start with a $300 barrel (yup, I'm cheap) what is the add on to have it treated?
Click to expand...
If it’s done already it’s too late.
 
#32
Rocketvapor said:
The problem with melonite barrels is the extra cost of having a single, or two done.
Especially if it's not a normally stocked configuration.
Buying one from someone that does exactly what you want in larger lots is hard to find.

Start with a $300 barrel (yup, I'm cheap) what is the add on to have it treated?
Click to expand...
The batch fee runs $500-$1200. At one time MMI would take in singles until they had enough to run a batch, not sure if anyone still does that.
 
#34
I'm glad to see this, actually. I have a Bartlein I'm running in a Valkyrie. I pulled it apart after the initial 140 rounds because it had quit running. To my amazement, everything was covered in thick fouling. Based on the green color, I deduced it's copper coming from the gas port. It had completely clogged up the works (copper in the gas rings) and had even "plated" the hammer.

I spoke to the guy who chambered it for me and he said he'd seen that a few times. He thinks it will go away on its own. My hope is that I got some erosion of the hole and that will eliminate the problem. I'll clean it all up tonight and try it again tomorrow. I'll also get a bore scope in it Sunday.
 
#37
Constructor said:
The gas port on a 18" RLGS is located in the same spot as a 20" RLGS so the pressure at the port is the same. We port the 18" and 20" barrels .093"
As for 4150 rusting, very few make untreated barrels unless it is a small smith/home operation. We have been Melonite/Nitride treating barrels since 2008 , they last longer and have better corrosion resistance than stainless.
Click to expand...

I was not referring to any particular brand, just that a Chrome-Moly barrel needs to be cared for. Clearly, Nitrided barrels are not the same, and i agree.

Your point on the barrel gas port is not the issue for gas port erosion. Of course, the gas port positioing is the same in any rifle-gas system. My point was that observed erosion is very pronounced on 18" barrels, due to the shortened distance to the muzzle compared to a 20." We have looked at hundreds of 18" barrels that eroded before their time, and this is due to the rapid exit of hot gasses prematurely on an 18" barrel, compared to a 20" barrel. And, in working with some of the best barrel shops I know of, for whatever reason, the Douglas SS barrels did not suffer as much erosion as other 18" barrels. Hope that clarifies.
 
#39
200 rounds.JPG

200 rounds total. Starting to pic up some copper.

Ran a boresnake through but have not cleaned the barrel.

Throat still looks great & Accuracy is great as well. (consistent sub moa groups with 69 smk & 24 grain Tac)
 
#42
Interesting to watch the rate of erosion appear to slow down as the edge rounds over.

Appologies for the diversion here but: @Constructor Do you nitride prior to drilling the gas ports? I was reading your post about step reaming vs drilling through the nitride crust and it made me curious. I assume the reduced tool life of the port drills is easily a better trade off than running three op's and increased tool cost of reamers. Any issues with flaking as the bit punches through or hardened (nitride) bur formation as the bit dulls?
 
#43
Vodak said:
Interesting to watch the rate of erosion appear to slow down as the edge rounds over.

Appologies for the diversion here but: @Constructor Do you nitride prior to drilling the gas ports? I was reading your post about step reaming vs drilling through the nitride crust and it made me curious. I assume the reduced tool life of the port drills is easily a better trade off than running three op's and increased tool cost of reamers. Any issues with flaking as the bit punches through or hardened (nitride) bur formation as the bit dulls?
Click to expand...
I do not, can't really. Barrels should be Melonite treated then the barrel extension installed, then gas port drilled. We can't drill the port until the extension is installed. Melonite treatment anneals barrel extensions that have been carburized.
I think the Melonite treated barrels are harder so the bits do not push the thin metal to the side, it cuts through.
 
#46
Constructor said:
The erosion would not bother me at all. The gas port going through the land like that and forming that point to rake copper off the bullets would.
Click to expand...
I’ve got a 6.5 barrel that has the port centered on a land. At 100 rounds I was pumped because it was hammering in the .3s. Accuracy fell off and after much tail chasing I scoped the port to find a huge mass of copper. I cleaned it off and accuracy returned. Since then I’ve cleaned every 100 or so and it’s getting smoothed out so it doesn’t grab much anymore. So I’d say being on a land matters, but can be dealt with by keeping it clean and letting it smooth out.
 
#47
Not bothered, since so far accuracy is holding up fine :)

It's not a fancy expensive barrel, if it were a $500 or so barrel then i would be, but not for what i paid for it. ( about $125 on sale)
 
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