Gas Block Qiestion

[Baddog0302]

The gas block that was installed on a 308 AR upper has a pin size hole on the top. About 3 range sessions ago I noticed the hole had black gunk in it, and also an occasional fail to feed or lock back. I'm thinking the GB has moved, but mI haven't been able to contact the builder.

Thought /comments

 

[Larryh128]

Is that an adjustable block?

 

[mac86951]

Looks like gas is seeking from around the gas tube to gas block pin. Could indicate something is out of alignment or a loose fit. Usually out of alignment will block gas causing cycling issues or leak between barrel and block. In this case, I'd estimate a poor Gas-tube to gas block fit, but it might just need a new gas tube roll pin.

-Mac

 

[EWaugh]

Some AR's are just dirtier than others. You might need to post a pic of the bottom of the gas block so we can see how the block is supposed to be secured to the barrel. From the first pic it shows to be dirty for sure and needs a good cleaning. And make sure to blow compressed air through the end of the gas tube to make sure that it is open. Also clean the BC key using a pipe cleaner. You should be good to go for another 100 or so rounds.

 

[Baddog0302]

Some AR's are just dirtier than others. You might need to post a pic of the bottom of the gas block so we can see how the block is supposed to be secured to the barrel. From the first pic it shows to be dirty for sure and needs a good cleaning. And make sure to blow compressed air through the end of the gas tube to make sure that it is open. Also clean the BC key using a pipe cleaner. You should be good to go for another 100 or so rounds.

It is not an Adj. GB, the builder of this upper said the "hole" is for an alignment pin. The GB area is .995". My plan is to clean the area , blow compressed air from the receiver end and the next range trip stuff the GB / tube area with poly fiber and watch if any get blown out due to a poor fit between the GB & tube.