Do you know any object-oriented prgramming (OOP) language. You cannot tweak a weapon by modifying the ini file. You need to code the gun with UnrealScript.
For the primary fire you need to look at the InstantHitMomentum variable. The variable is used in ProcessInstantHit. You could bascially mirror the value of the vector which is used for the TakeDamage function of an actor.
So, it could look like this:
The secondary fire is a bit more complex. My approach would be too create an own projectile. While this projectile flies through the world, it checks all overlapping Pawns and applies an impulse to the player "to fling" him into the core. This code for applying a force to overlapping Pawns can be taken from the Darkwalker (or Hero/Titan).
simulated function ProcessInstantHit( byte FiringMode, ImpactInfo Impact )
if (Impact.HitActor != None)
Impact.HitActor.TakeDamage( InstantHitDamage[CurrentFireMode], Instigator.Controller,
Impact.HitLocation, InstantHitMomentum[FiringMode] * (-Impact.RayDir),
InstantHitDamageTypes[FiringMode], Impact.HitInfo, self );
If you don't know aynthing about coding a mutator, you can check this tutorial. That article is a bit outdated, but works fine.