Missile's and wall's not getting along

Ok, well I have missiles shooting and colliding with walls.. works great and they even delete themselves at the wall.. but thats where the fun ends and the problems begin..

ok a little code..

function playerFire()
{
// Create player projectile.
%projectile = new fxStaticSprite2D() { scenegraph = t2dSceneGraph; };
%projectile.setSize( "3 1.5" );
%projectile.setImageMap( playermissileImageMap );
%projectile.setLinearVelocityX( 35 );
%projectile.setPosition( $player.getLinkPoint($player.fireLinkPoint) );

// Setup collision info
%projectile.setGroup( 1 );
%projectile.setLayer( 0 );
%projectile.setCollisionPhysics(true, false);
%projectile.setCollisionActive(true, false);
%projectile.setCollisionMaterial(freeflowMaterial);
%projectile.setCollisionScale("0.9 0.5");
%projectile.setCollisionMasks(0xffffffff, 0xffffffff);
%projectile.setCollisionCallback( true );

}

function createExplosion( %object )
{
// Ignore if object not around anymore.
if ( !isObject(%object) )
return;

// Shockwave Explosion.
%explosion = new fxParticleEffect2D() { scenegraph = t2dSceneGraph; };
%explosion.loadEffect("t2d/client/effects/shockwave_burst.eff");
%explosion.setPosition( %object.getPosition() );
%explosion.setEffectLifeMode( kill, 0.5 );
%explosion.playEffect();
}

now when it explodes at the wall the explosion appears at the center of the tile map and not at the wall...
not very realistic.. :)

I am thinking that its a oncollision callback but not sure how.. :)