AR15 gas port burr removal?

[RU shooter]

Aluminum is surprisingly abrasive. Most aluminum rods are jointed and flexible enough that even with a proper bore guide they can rub on the bore. If it is done a lot in the same place you are in effect lapping that area. I do have a couple of joined aluminum rods for emergency field use. Other than that they will need see the inside of a rifle bore.

I've heard this before and my question is the why ? Is it because aluminum is so soft and easily gets "grit" embedded into it ?

[Vettepilot]

It's because of aluminum "rust". Aluminum oxide forms on aluminum, almost instantly. This actually protects the aluminum and is why it doesn't appear to degrade like other materials such as bare steel. The aluminum oxide is VERY hard and abrasive, even though it is a quite thin layer on the surface of the aluminum.

The aluminum itself, being soft, can also get foreign matter imbedded into it, as you suggested.

Vettepilot

[Vettepilot]

Aluminum oxide is commonly sold as sand blasting media, and is also used as the grit on some sandpapers.

Vettepilot

[popper]

Interesting factoid - gas key hole is 'small' so nothing to speak of get in there! Looks like an orfice at the back of the key hole. NO big chunks in the BCG!. Glad you got it out I never worried about it. I put a wooden dowel in mine when enlarged, use slow twist drill and tapped the dowel out - burr was gone.