030-inch. Engineers also shortened the case to help make the cartridge friendly to long lower-drag bullets which have high ballistic coefficients. The 6mm ARC was made all over best use by using a 108-grain bullet. Streamlined secant ogive with the best possible boattail structure + highly concentric AMP bullet jackets https://6mm-arc-ammo18518.blogsuperapp.com/21862482/6mm-arc-ammo-options