What is the true bore size on a 58 cal .musket?

The true bore size of a .58 caliber musket, such as the Springfield Model 1861, is approximately .577 inches in diameter. The designation ".58 caliber" refers to the nominal size of the bullet or projectile, not the exact bore measurement, which can vary slightly due to manufacturing tolerances. The actual bore size is often slightly larger than the caliber designation to accommodate the bullet and allow for ease of loading.