Gas port erosion...

[Ridgerunner665]

I understand what it is and how it occurs...but how much will it erode?

Will it erode enough that springs and buffers wont fix it?
How many rounds before it becomes a problem?
And any other useful info you may have on the subject...:)

I'm new to AR's... I'm trying to learn what to watch out for. Thanks

[Robb Jensen]

I understand what it is and how it occurs...but how much will it erode?

Will it erode enough that springs and buffers wont fix it?
How many rounds before it becomes a problem?
And any other useful info you may have on the subject...:)

I'm new to AR's... I'm trying to learn what to watch out for. Thanks

For 99% of the people out there most of the time you'll wear out the throat of the chamber causing really poor groups (more like patterns) before the gas port is eroded. It can be fixed. I requires drilling out and tapping the gas port and installing a set screw, then drilling a new gas port through the set screw.

[Ridgerunner665]

For 99% of the people out there most of the time you'll wear out the throat of the chamber causing really poor groups (more like patterns) before the gas port is eroded. It can be fixed. I requires drilling out and tapping the gas port and installing a set screw, then drilling a new gas port through the set screw.

Thank You Sir...thats what I wanted to know.... I had searched for it but didn't find it.

[scottryan]

For 99% of the people out there most of the time you'll wear out the throat of the chamber causing really poor groups (more like patterns) before the gas port is eroded. It can be fixed. I requires drilling out and tapping the gas port and installing a set screw, then drilling a new gas port through the set screw.


At which time you might be better of buying a new barrel depending on one's situation.

[Robb Jensen]

At which time you might be better of buying a new barrel depending on one's situation.

If the throat erosion is okay but the gas port is too big, then yes for the less skilled armorer/gunsmith a new barrel would be probably the best option.

[Ridgerunner665]

Does it require any special tools to remove an AR 15 barrel...I'm no gunsmith...but I am a Master Tinkerer, I've looked at the barrel and just by guessing I'd say remove the handguards, remove the upper, remove the front sight/gas block (all of which is pinned in place)....then heres where it gets hard to see without taking it apart...to get the barrel loose...does it just unscrew from the receiver, or is it connected to the lugs somehow...

Is that even close to how it goes??? If not...educate me please.:)

[ST911]

For 99% of the people out there most of the time you'll wear out the throat of the chamber causing really poor groups (more like patterns) before the gas port is eroded. It can be fixed. I requires drilling out and tapping the gas port and installing a set screw, then drilling a new gas port through the set screw.

More info? My first thought is what would keep that screw from becoming an eventual/possible bore obstruction?

[Ridgerunner665]

Loctite or a spot weld...maybe...just a guess.

[Edward Hogan]

So, what causes gasport erosion?

I'm guessing not having the gasblock correctly centered over the hole?
Would another fix be to install a variable flow gas block?

[Ridgerunner665]

So, what causes gas port erosion

Hot gas and small particles flowing through a small hole under high pressure....it has an affect similar to a bead blaster (or sand blaster)

[Robb Jensen]

More info? My first thought is what would keep that screw from becoming an eventual/possible bore obstruction?

You don't drill and tap all the way to the rifling. Just far enough to hold the set screw. The set screw is a 4-40 x 1/8".

[ST911]

You don't drill and tap all the way to the rifling. Just far enough to hold the set screw. The set screw is a 4-40 x 1/8".

Interesting.

I've got a buggered-up barrel in a parts bin this might be worth trying. The previous owner opened up the gas port to "improve" that which did not need "improving."

Are you using a particular type of set screw (grade/hardness/design/etc)?

Any particular cautions or advisories for the process?

[Iraqgunz]

When I was working at a large training facility in North Carolina we used a Hawkeye Borescope to check the gas ports. It was decided that although the weapon passed headspace and throat erosion checks, time is money and changing them after the gas port became enlarged was the best way to go. These weapons were seeing alot of use and not receiving the proper maintenance and PMCS due to the volume of training.

[Robb Jensen]

When I was working at a large training facility in North Carolina we used a Hawkeye Borescope to check the gas ports. It was decided that although the weapon passed headspace and throat erosion checks, time is money and changing them after the gas port became enlarged was the best way to go. These weapons were seeing alot of use and not receiving the proper maintenance and PMCS due to the volume of training.


Interesting. I find that typically the gas port does in fact enlarge and changes shapes and but many times it stops. It's just like the locking block peening on the bottom of a slide on a .40 cal Glock......it's gets to a point and stops.

On the AR I find at that point going to a heavier buffer (depending on the size of the port) will slow it back down, sometimes this is as heavy as a H2 or H3 buffer. For a large facility this may not be an option (cost wise for labor) but if a buffer corrects the high cyclic rate vs changing a barrel what would it hurt? If I think I know who the NC facility is that you're talking about is, then they use(d) Bushmaster which come with CAR buffers.

This is one of the areas where having a premium 4150 or better barrel makes a big difference. Some barrels have throat erosion and gas port erosion faster than others. If you're going to run your AR hard and fast (in very short time) it pays to get a good barrel.


Interesting.

I've got a buggered-up barrel in a parts bin this might be worth trying. The previous owner opened up the gas port to "improve" that which did not need "improving."

Are you using a particular type of set screw (grade/hardness/design/etc)?

Any particular cautions or advisories for the process?

See this thread.
https://www.m4carbine.net/showthread.php?t=6499&highlight=port

[ST911]

See this thread.
https://www.m4carbine.net/showthread.php?t=6499&highlight=port

Forgot about that one, thanks.

[Iraqgunz]

Gotm4,

Basically I was doing much needed TI's on them. The armory sup said to replace them if they were elongated. I also checked the gas rings, key carriers, etc....and replaced whatever needed it. Once cleared, did a test fire and racked 'em back up. They just didn't needlessly want to have Junkmasters going down during training.

[Robb Jensen]

Gotm4,

Basically I was doing much needed TI's on them. The armory sup said to replace them if they were elongated. I also checked the gas rings, key carriers, etc....and replaced whatever needed it. Once cleared, did a test fire and racked 'em back up. They just didn't needlessly want to have Junkmasters going down during training.


http://img.photobucket.com/albums/v408/gotm4/smilies/uglylol.gif

[ARin]

GPE is the reason that many new carbines wont run a 9mm buffer reliably, but older guns will.

[Robb Jensen]

GPE is the reason that many new carbines wont run a 9mm buffer reliably, but older guns will.

How does that logic work?

[ARin]

brand new tight gas port often doesnt gas enough to handle the extra weight of a H3 or 9mm buffer. the system will short stroke....performing as if "undergassed".

as the port erodes, you get more gas, necessitating the use (or "allowing" the use) of heavier buffers.



remember, heavier buffers have the same effect on the system as reducing gas and vice versa.

[Robb Jensen]

GPE is the reason that many new carbines wont run a 9mm buffer reliably, but older guns will.



brand new tight gas port often doesnt gas enough to handle the extra weight of a H3 or 9mm buffer. the system will short stroke....performing as if "undergassed".

as the port erodes, you get more gas, necessitating the use (or "allowing" the use) of heavier buffers.

remember, heavier buffers have the same effect on the system as reducing gas and vice versa.

From the way you worded the your 1st GPE comment it made it sound as if after the gas port erodes it won't work with 9mm buffer. That's why I was questioning the logic.

[ARin]

well thank god!:D

i was actually really surprised that i had to explain myself.:eek: :p

[Robb Jensen]

well thank god!:D

i was actually really surprised that i had to explain myself.:eek: :p

Yeah I've been around the block a time or two and know a little bit about gas port erosion among other things. ;)