Left to right: .280/30 British, 7.62x39mm M67, 5.56x45m M855, 6.8x43mm SPC XM68GD, 6.5x38mm Grendel 123gr Lapua Scenar, 7.92x33mm Kz.Ptr.43 sME. All of these rounds have different characteristics that affect their ballistic performance and their reliability in automatic firearms. We’ll be taking a closer look at these characteristics to better understand the trade-offs in small arms ammunition design.