Sig Sauer 300Blk 220gr Supersonic Otm Ammunition features 220gr Sierra Match King Projectiles for superior accuracy and minimal dispersion when suppressed. The Open Tip Match or OTM is a full metal jacket design manufactured to provide superior accuracy and penetration at a variety of ranges. Sig Sauer 300Blk 220gr Supersonic Otm ammo was designed to bring out the best in today's high-performance AR rifles.