As best I understand, companies of the 2nd AVC regiment later became the 5th Alabama Regiment which went to Richmond VA. Companies of the 1st AVC which occupied the Mobile Bay forts formed the basis of the 3rd Alabama Regiment which went to Norfolk VA, while companies of the 3rd AVC regiment formed the first Confederate regiment accepted in military service as the 1st Alabama Regiment. This command remained at Pensacola during the entire year of 1861.
The newly independent State of Alabama organized the Army of Alabama in February 1861. Recruiting officers were sent to cities throughout the state to secure men willing to enlist for five year terms. Enough officers and men mustered to form a battalion of six companies. These were assigned to garrison to Mobile Bay forts and were turned over to the Confederate government in May 1861 as the 1st Alabama Artillery Battalion. In some accounts they are called "regulars". This is due to their original enlistments in the Army of Alabama.