Faxon ar barrel problems

[Shadow9mm]

Originally Posted by stagpanther

It could have been any of those things--or something else. If it were a complete upper or rifle it most likely would have been test fired to see if everything was in order. Because a barrel is delivered with a block already pinned--the purchaser is completely reliant on the manufacturer for having cut the pin slot, done the install etc. I don't even want a slot cut into my barrel that's going to be hammered at from the side--but that's a different argument. It's no trivial matter sliding the block on and off to adjust the gas flow--not to mention examine the port when its been pinned to the barrel. Unpinned blocks generally seal with carbon deposit; I've never had one move or come off easily.

I think this is a "classic" argument of "ultimate reliability." If so called mil spec battle ready is a requirement--go for it, pin by all means. I think it gets dodgy when talking about modular building and maintenance--no way I'd do it.

I installed the pin. Faxon uses a roll pin not a taper pin. But it is all pre-drilled at the factory. As best i can tell everything is straight. And the gas marks look even, radiating from the hole in the gas tube. I will post more pics after work tonight.

At this point im hoping faxon will take the barrel back and i can get a replacement model without a pinned gas block so i can try an adjustable gas block in case its over gassed.

[stagpanther]

My apologies to you and DubC-Hicks--I was being a bit of a jerk about it--I thought the barrel came assembled with the gas system install already done.

That gas cutting on both sides of the handguard is pretty impressive, I've never seen anything like that before.

[Shadow9mm]

Originally Posted by stagpanther

My apologies to you and DubC-Hicks--I was being a bit of a jerk about it--I thought the barrel came assembled with the gas system install already done.

That gas cutting on both sides of the handguard is pretty impressive, I've never seen anything like that before.

Sorry if i wasn't clear. Gas block came pre-drilled with an included roll pin ready to be installed. However since it was pre drilled it should have been fixtured and alligned when it was drilled at the factory, so imho its pretty close to the same thing you were talking about. Especially given that with the roll pin installed that is what alligns the block, i have no wiggle room to adjust it.

Yeah, it is impressive gas cutting. Iv never seen anything like it either. Wish i didnt get to be the test case, but at least i have something cool fror show and tell that we can learn from

Im gonna take the block off tonight and try to measure the port diameter.

[stagpanther]

What's the gas system length?

[DubC-Hicks]

Im gonna take the block off tonight and try to measure the port diameter.

Faxon's spec that I found online for your barrel is .0810". For comparison, the BA .625 profile Hanson 16 middy is .0760".

[Shadow9mm]

So faxon responded. Im a bit in shock. They stated it is normal. I know its not uncommon, but never to that level.

"The port on the gas block for the gas tube is spec .181±.002-.000. The port is made to be a slip fit, not pressed, so the tube may have a little bit of movement. What you are seeing is pretty normal, and should not be the cause of accuracy issues.


Respectfully,"

[ballardw]

Originally Posted by Shadow9mm

So faxon responded. Im a bit in shock. They stated it is normal. I know its not uncommon, but never to that level.

"The port on the gas block for the gas tube is spec .181±.002-.000. The port is made to be a slip fit, not pressed, so the tube may have a little bit of movement. What you are seeing is pretty normal, and should not be the cause of accuracy issues.


Respectfully,"

Will Faxon pay the hospital bill for when the gas finishes cutting through the handguard and starts on the hand?

[DubC-Hicks]

Well, since you're seemingly stuck with the barrel, you could try an adjustable block on it.

I'd still pull off the block and measure the gas port if possible. It shouldn't be blowing that much gas out of the gas tube roll pin hole AND be gassy enough back near the receiver to be stinging your eyes. I've owned, shot, or built for others, at least a dozen rifles using Faxon barrels. And most have been slightly over gassed, but easily tamed with an H or H2 buffer. Definitely nothing like what you're seeing.

[Shadow9mm]

gas tube pics, left side, center, right side

[Shadow9mm]

Ok, so I am going to be pulling the flash hider and gas block tonight. going to measure the gas tube hole in the gas block, and the gas port size in the barrel.

I have considered a adjustable gas block. Looking at the one from aero precision. However there is no guarantee it will fix the accuracy issue.

Faxon recommended i shoot some gold medal match with no muzzle device. I already bought the ammo. I am going to test it 1 more time. They said they would look into replacing it if it still did not shoot well with that ammo. I told them I would give it 1 more try and I am going to.

[stagpanther]

Can you get a borescope down that puppy to look at the gas port? If you're getting that kind of cutting outside the port it could be doing damage to the port inside the barrel as well. I've seen gas ports that straddled the bore and rifling with irregular edges that can tear at the bullet as it goes by--especially if the port has started to erode (starts to get more oval-like). Should be easy to spot with stubborn copper "tailings" between the port and muzzle.

[Shadow9mm]

I can, but it will be tomorrow. Got too busy tonight to get anything done. However I use bore tech eliminator, which has a copper remover in it. so there may not be any copper to see.

[stagpanther]

I can, but it will be tomorrow. Got too busy tonight to get anything done. However I use bore tech eliminator, which has a copper remover in it. so there may not be any copper to see.

Gas port drilling--when not done well, is one I see pop up every now and then as a "hidden accuracy killer." Larger size ports can overlap both the rifling and bore, sometimes leaving an edge that promotes tearing of the bullet and erosion of the port. Even with a clean bore it should stand out if the port has eroded, the same kind of cutting you see on your handguard might be eating away at the barrel where the port is drilled through, which also has the effect of increasing the gas flow.

[ocharry]

i have seen gas blocks have some leaking before but nothing like that...and after they get some rounds down the tube they do kinda stop...plug the leaks

i think if you are having that much gas out the front at the block and you are getting gas in the face at the breach then logic would tell me that the gas port is way to big

if you put an adjustable gas block on that barrel i would want one that also vents...i think the superlative gas block company (not sure if that is right or not) makes one like that..they vent out the front of the block and is ajustable so you can dial it down to only use the gas you need

what barrel length and gas length did you say you had??

i just dont see how beeing over gassed or way over gassed or under gassed has anything to do with how accurate the barrel could be....well i guess if it is way over gassed.... ie. large hole going into the bore could cause it to do something stupid i guess

ocharry

[Shadow9mm]

16in barrel, mid length gas

My thinking was, if its venting gas out the roll pinn that retains the gas tube, the gasses are essentially pushing on the barrel, which woukd effects the consistency of the barrels harmonics. Like a cheap plastic stock flexing and touching the barrel.

I am looking at the aero precision block which is just a cut off type. I dont want to vent gas. They also make gas tubes with restrictions that might help.

[stagpanther]

For the moment--my money is on damage/erosion to the port itself where it goes through the barrel--that could account for both the overgassing and a bullet upset.

[ocharry]

so i guess the question would be then ...how many rounds down the barrel??? is it a new barrel...or lots of rounds down the tube??

i could see stags point if it has been shot a lot...port is egged out caused by excessive gas flow ..maybe that little hole erodes faster than i think it does...and that thing sounds like it is way over gassed...and that is really hard on the rest of the working parts..slamming around

i get it why makers do that...so the thing will run anything you put in it...my son in law has a S&W 15 that is way over gassed..i had to put a H2 buffer in it to get it slowed down and i think i could go heavier....but yours sounds worse than his

i would like to know what size the gas port is..do you have gage pins?? or number drills you could use?? number drills usually have pretty small size changes...like maybe a thou or two from size to size

i would think if you are worried about accuracy and barrel harmonics taking a slice out of the radius of the barrel for the pin to go through would be the last thing to do for accuracy...just like dimpling you have upset the radial structure of the tube...made a weak spot so to speak causing the whip or vibration or harmonic to change at that spot....you can do the same thing with barrel pressure or dampening or weight on the end..like a suppressor....anything to change the natural flow of the whip harmonics is gona change accuracy..i have seen guys wrap tape around their barrels in different spots to change the harmonics...and it does work..just my thoughts on barrels

ocharry

[Shadow9mm]

All new, faxon barrel/gas block. Odin works tube. Approximately 400rnds through the barrel. Grouping 2.5 to 4moa with 2 cheap factory and 3 good hand loads

[603Country]

Just go ahead and buy a new high end barrel. Some barrels just don’t shoot well and you can’t make them do it. Quit fighting the Faxon.

[stagpanther]

i could see stags point if it has been shot a lot...

Not really--all it takes is for the erosion to get a foothold under the harder bore layer and it can go pretty quickly with not that high of a round count--seen it happen.

Grouping 2.5 to 4moa with 2 cheap factory and 3 good hand loads

That's not really far off from what I'd expect in bulk ammo in a "mil spec" barrel.

[Shadow9mm]

I would agree, however these loads shot 1.25 to 2.5moa out of the old $90 brownells barrel that was on my gun. And have shot similarly in other ar's. That $90 barrel is now on my suns build, though i bought an upgrade. Apparently not ao much.

[stagpanther]

Get that borescope down there and look at the port!

[ocharry]

Could just be you havent found the magic combination for that barrel...and like 603 says you may never find it

But that still dont answer or fix the over gas problem

I sure wouldnt like that thing gassing in my face...I guess a adjustable gas block could maybe fix that.....I like to control the mass and then the gas...just me

For sure you need to have a look at that gas port....inside and outside too

Ocharry

[Shadow9mm]

By popular demand here is the gas port. It had a bit of crud in it. I cleaned it out with a tooth pick as best I could. Top of the photo is towards the muzzle.

Also, no pin gauges. I measured as best I could with my calipers, I got 0.072

[Shadow9mm]

Also I got in the federal gold medal match 77g. I picked up a box of winchester M193. And I am getting 20rnds of IMI 77g razor core from a co-worker to test. As of now next day I can get to the range is monday, and it is a 50% chance of rain. hoping things clear up by then.

I told Faxon I would test the Federal GMM and I am a man of my word. But I am done after this.