What is the minimum bearing surface length for something like a 5.56 (or really any militarily viable cartridge)? And what is the optimal length? Surely there is a point after which one gains nothing from increasing this length. So how short could you go without sacrificing whatever it is that is sacrificed with a short bearing surface. Concentricity in engraving, maybe?

Picrel is a 5 caliber long bullet I modeled with a 1.4 caliber long bearing surface. Its i7 form factor is 0.8. I wonder if it’s possible/sensible to shorten this even further and add the saved length to either the ogive or the boat tail