I seem to recall that the Bolsheviks overthrew the Provisional Government, and that the Socialist Revolutionaries fought against the Bolsheviks in the Civil War.
Yeah, depends which SRs, and what period. Some of them definitely formed local governments which fought against the Bolsheviks (to restore property to landlords and allow punitive expeditions to hang the revolutionary peasantry in peace). Didn't help them when they got executed by the Whites in the end, of course, despite being so helpful.
A few others imposed Red Terror along with the Bolsheviks. It was a complicated time, except for the whole "hanging peasants" thing. Everyone seemed to get that part instinctually.