Checking for leaks after getting slower velocities found white buildup

[Labrat198]

I know gas blocks typically leak and will build up carbon, but shouldn't it be black?

Ran about 250 rounds through it so far. 150 American Gunner and the rest hand load ladders. I was getting slower than expected velocities for my ladder work (the american gunner clocked at 2206 fps for a reference). I don't think I was shooting at an angle, but its possible. This was also my first time with the Caldwell Chronograph, could just be the mileage I get with it. Anyway, when I pulled the handguard off to check the gas block it didn't have the black build up I was expecting to see.

I have a 18 inch group buy RLGS
Wojtek Gas Block
standard 3 ounce carbine buffer and buffer springs
temp as about 30 F
IMR 8208 XBR was the powder in the hand loads

gas block5.jpg

[NugginFutz]

It is highly unlikely that a gas leak at the gas block, no matter how severe, is going to make a noticeable difference in MV. You would have to remove the GB entirely to see anything even remotely measurable. By the way, AG is known for its comparatively low MV.

As far as the white residue is concerned - All the blow by I've ever seen has been sooty or black.

Are the GB screws torqued properly?
Did you bed the GB with loctite?
Was there any kind of sealant or paste on the inside of the GB when you installed it?
Prior to installation, did you clean the GB to remove any preservatives?

These are all the possible sources I can imagine. I would suggest removing the GB and inspecting both it and the gas port for any signs of foreign matter or erosion, while you have it apart.

I'd also ensure you store the rifle where the gremlins can't put flour down the barrel while you sleep as a practical joke.

[BCHunter]

Looks to be leaking on the GB adjustment screw, could be preservative or sealant there.

As for color anything in your reloading process that might effect it? Lube left on cases, media left in case? What powder are you running some are noted for being sootier then others?

[Labrat198]

I wiped the barrel and GB down with a light oil/solvent saturated cloth to clean the area up just before installation, other than that I put it together dry. Wojtek says to only hand tighten the clamping screw, so I torqued them to 20 in/lbs if I remember correctly. I will pull it apart to see what I find and report back later.

I think the adjustment screws came installed, so there could be something to that.

I ultrasonic my spent brass, then rinse and dry, spray with One Shot Case lube, then size. Could be water deposits but that seems like a stretch when the GB is the only place its showing up, BCG is all the typical black carbon.

So far it has just been IMR 8208 XBR and whatever AG uses for powder.

[Labrat198]

And thanks for not assuming I am doing lines off my barrel.

[NugginFutz]

And thanks for not assuming I am doing lines off my barrel.

You can do that? Can't wait 'til I get home to try it!!!

ETA: Which is better - CFE223 or IMR8208 for doing lines?

[Klem]

Labrat,

I have seen this in suppressors that are left uncleaned after firing. You can find a few pictures of this on Google images;


A combination of carbon, moisture and unburnt powder left untouched for a while. On lower velocity rigs lead vapor also mixes to form corrosive salts. The white powder is not visible immediately after firing but in time it forms, especially in a humid environment.

The seal of your gas block is leaking. This is not unusual in AR's as gas blocks are not designed to be hermetically sealed. Usually there is plenty of gas to cycle the action so a small leak here and there is no big deal. You just need to spray WD40 on that spot every now and then and wipe it off. If you wipe down and spray the metal surfaces of your gun on a regular basis you will never see this (I leave the inside barrel uncleaned to save the zero and wipe the outside. Then store it with corrosion inhibitors like vapor capsules in the safe and a length of barrel strip, https://www.zerustproducts.com/produ...n-tube-strips/ )

[Labrat198]

gas port.jpg

Doesn't look like anything concerning is happening inside. Going to give everything a good cleaning and just monitor from now on.

[Labrat198]

sorry, that picture looks way out of focus after I cropped it...

[A5BLASTER]

[ATTACH=CONFIG]14055[/ATTACH]

Doesn't look like anything concerning is happening inside. Going to give everything a good cleaning and just monitor from now on.

Gas scar around the port looks like the gas block was placed perfectly. Gas port looks a lil out of round but that could be the pic itself making it look like that.

As far as the leak goes, I wouldn't worrie bout it much. Clean it off with wd40 when you see it forming and before long the leak will fill up and stop.