SIG Sauer Introduces Supersonic 300BLK SBR Elite Copper Duty Ammo by Craig Fernandez | Feb 14, 2019 | eNews | 0 comments SIG Sauer Inc. is introducing its newest 300BLK ammunition – the 120gr supersonic 300BLK SBR Elite Copper Duty load, specifically designed for short barrel rifles. Read more from source... Submit a Comment Cancel replyYou must be logged in to post a comment. This site uses Akismet to reduce spam. Learn how your comment data is processed.