Yes, but changing the cvar affects everything.
The code for the behavior of this projectile is in g_weapon.c, the function is "static void WP_RepeaterAltFire( gentity_t *ent )", it's at line 1074.
To make it descend slower, just alter the line:
missile->s.pos.trDelta += 40.0f; //give a slight boost in the upward direction
as you see fit. What i'd do is make a server side cvar, tie it to missile->s.pos.trDelta and then play with the setting to get it where you want it.