Accuracy of an Infantry Carbine is somewhat subjective :)
The barrel is .577 and the bullet is a .575, .002 undersized.
The design of these Minie's really negates the need to size your bullet as the cup is very deep and the lead 'skirt' is soft enough to flare out into the groves on ignition.
This is a pic of the cup and a .45 cal ball....you can see how low into the cup the ball sits, the cup captures the blast and forces the side walls out.
http://i125.photobucket.com/albums/p...pslnfypgn2.jpg
http://i125.photobucket.com/albums/p...psf2tjzqor.jpg