I have a barely used Rainier Arms 8.5" UltraMatch Barrel chambered in 300 Blackout.
Barrel has exactly 47 rounds through it.
(PP+3.5%, PP FF, USPS MO)
Would trade for a SPR barrel of similar quality
Stainless Steel Match Grade Shilen Blank
Gas Block Seat: .750 Diameter
Pistol Length Gas System
Thread Pitch: 5/8X24
300 AAC Blackout Chamber
M4 Feed Ramps
Bead Blasted Finish
More pics upon request: