Colonel Coote Manningham, responsible for establishing the Rifle Corps, influenced the initial designs of the Baker. The first model resembled the British infantry musket ("Brown Bess"), but was rejected as too heavy. Baker was provided with a German Jäger rifle as an example of what was needed. The second model he made had a .75 caliber bore, the same caliber as the infantry musket. It had a 32-inch barrel, with eight rectangular rifling grooves; this model was accepted as the Infantry Rifle, but more changes were made until it was finally placed into production. The third and final model had the barrel shortened from 32 to 30 inches, and the caliber reduced to .653, which allowed the rifle to fire a .625 caliber carbine bullet, with a greased patch to grip the now-seven rectangular grooves in the barrel.