I am searching for a new match barrel for an AR 15 it needs to be 20" so i am thinking about a SDMR profile.
I will be using NATO and match ammo, what chamber?
As i will do some rapid fire sessions, would a CM vs SS? no chrome line as i needs this to be as accurate as possible.
Thinking about 1 in 8 twist best for all round use.
What blank to use? would a 5R/C barrel be better?

Thanks

These are  great!  http://www.superiorbarrels.com/

White Oak Armament SDMR barrel.  It has all the specs you listed.