Most certainly, at least in the initial stages.
As modern countries infrastructure is geared towards facing an external threat, the fragmentation of this in a civil war does cause shortages and supply problems. The advantage then tends to go to the side that overcomes these problems first. In the SCW the Republic had the manufacturing base, but was fragmented politically, which led to difficulties over distribution of equipment and ammunition. The Nationalists received a mass of equipment from (relatively near) foreign powers, overcoming their short term disadvantage. The English Civil War was similar, in that the Royalists never really overcame the difficulty of bringing in powder and weapons from the continent. The Parliamentarians had control of domestic production and easier import routes.