Actually, Sectional Density (SD) has no influence on accuracy at all. Nor, with modern bullets, does it have any meaning for predicting penetration.
Consider this; ALL bullets of a given diameter and weight have the same SD. It makes no differnce if it's a hollow point, spire point, round nose, thin jacket, full metal jacket, fused core, a solid or partition, if they are the same diameter and weigh the same they have the same SD. No way will they give equal penetration.
Back in the dark ages of bullet making, say 50 years ago, bullets tended to be simple "cup and core" with a few distinct exceptions like Nosler and Barnes bullets. Nothing bonded the jacket to the cores so light bullets at high velocities tended to rupture and often failed to penetrate far. The only way to get greater penetration was to use a heavy (for caliber) bullet, which insured a lower terminal velocity and greater mass to help it carry through.
Modern bullet makers have changed all that. A light Barnes (and others) with a low SD will out penatrate a heavy for caliber soft point bullet with a thin jacket even tho it has a higher SD.
