question on "burr" in AR barrel

[jonkertb]

I finished an AR build awhile back, never shot it so decided to strip and lube it and run a patch down the barrel this past weekend...it seems there is a burr at the hole / gas port at the top of the barrel as it shreds a cotton patch in that area.
Is this typical and will it hurt to shoot it? Will shooting it clean this up or should I notify the vendor and try and return it.....it may have been too long for this?
thanks
tom

 

[bigdaddy1427]

You should be able to feel the gas port, but there should not be enough of a burr to shred a patch! It should be safe to fire, but I can only imagine what it would do to a copper jacket at 3000 + fps the first couple of times.
If you have never shot it, it may go away after firing a few rounds and it works itself out.

 

[fireball168]

Many quite experienced folks, including some barrel manufacturers will tell you to shoot it out.

Many other experienced folks figured out if they drill the gas port in two steps or more, it doesn't create that burr.

Some folks - myself included, drill the port in two steps - with a closely fitted dowel rod in the bore. Once I see wood - I stop drilling. I then push a lubricated dead soft lead slug into the burr that was formed - and go up 1-2 drill sizes for my finished gas port size. Push the sinker out after your done drilling. There is never a burr when I'm done.

You can remove the existing burr the same way - ideally, you'd want to remove the FSB/gas block - push a dead soft lead sinker down the bore(as in slugging) until you feel the restriction. Most times the burr just falls off into the lead. Some times the burr pushes back up into the gas port - then push it back into the bore with an appropriately sized drill bit/pick/torch cleaner. They usually will bend once, and fall off the second time.