is this thing I saw from the groove concerning?

[exoto1225]

Hi guys,

I have a 20' Rainer Ultramatch barrel in 223 wylde on my SPR AR built. I put ~5k rounds through it. I always shoot slowly, let the barrel cool and use very mild load (23.5 gr IMR4064, 2700 fps for 69 gr smk). I recently observed some marks on the groove that look like this

from the chamber side (forgive me for the terrible drawing, try to catch what I saw with my phone but it's too hard to see from the camera). I am pretty certain those cannot be removed by cleaning and was not there before (the groove was very smooth before). The rifle still shoots nice groups, should I be concerned? Thank you!

 

[PinesAndProjectiles]

If it still shoots, keep shooting.

More often than not, using a bore scope leads to looking for a problem that doesn't exist.

 

[clcustom1911]

Those areas are where all the really, really high temperature stuff happens. Imagine shoving about 45,000-50,000 psi of really hot gasses down a small hole behind a metal plug (bullet). Youre bound to have some kind of buildup.

Good news: its perfectly normal. Keep shooting and clean regularly or as often as makes you happy. You'll get 200 opinions from 100 guys about cleaning.