Is this typical?
I just noticed so I checked my RRA NMA2 that I've fired 10x as many rounds thru and it is there as well though much less obvious.
About 200 rounds
http://www.danpassaro.com/img/s8/v83/p1632814525-4.jpg
http://www.danpassaro.com/img/s10/v1...50820073-4.jpg
http://www.danpassaro.com/img/s9/v87/p1656748000-4.jpg
http://www.danpassaro.com/img/s10/v1...12497300-4.jpg