From The Manufacturer/Wikipedia/People Smarter Than Us:
The FN 15 DMR includes many of the same features as the FN 15 Sporting but was designed for more tactical applications. The FN 15 DMR features an 18” match-grade, cold hammer-forged barrel with a 1:7 twist to enhance stability and accuracy for heavier grain precision shooting ammunition. It also comes with pre-installed Magpul MBUS Pro backup iron sights, Midwest Industries SSM M-LOK 15″ hand guard with a 1913 rail for mounting optics, night vision or thermal devices.