You must be right about the two flank companies (A and B) being issued rifles at the outset since the company names reflect that fact, Company A being the "Acworth Rifles" and Company B being the "Newton Rifles." Dean Thomas's book on small arms at Gettysburg indicates that the majority of soldier's in McLaw's Division were armed then with .577 caliber Enfield or .58 caliber Springfield weapons based on recovered bullet specimens. By the way, Company A of the 3rd Battalion Georgia Sharpshooters, which was formed in June 1863, was comprised of soldiers from the 18th Georgia.