Customise particular RSS permalink

From my old static website, I want to preserve some URLs like the RSS Feed one.
My feed URL is http://traduction.bainslesbains.com/actualite-russe.xml and I want to redirect it to the category feed URL WITHOUT 301 redirect.

So I tried it via .htaccess file first, what is not working. Then I tried via internal WordPress URL rewrite system.

So first I did this:

// Rewrite actulaite-russe.xml
function feed_dir_rewrite( $wp_rewrite ) {
    $feed_rules = array(
        'actualite-russe.xml' => 'index.php?cat=8&feed=rss2',
        'actualite-russe.rdf' => 'index.php?cat=8&feed=rdf' . $wp_rewrite->preg_index(1)
    );

    $wp_rewrite->rules = $feed_rules + $wp_rewrite->rules;
    return $wp_rewrite->rules;
}

// Hook in.
add_filter( 'generate_rewrite_rules', 'feed_dir_rewrite' );

That give me a 301 redirect from

mysite.com/actualite-russe.xml to mysite.com/actualite-russe.xml/feed/

I don’t want any 301 redirect I want just been delivered my feed without redirect. So I tried this:

add_action('init','feed_dir_rewrite');
function feed_dir_rewrite(){
        add_rewrite_rule('actualite-russe.xml','index.php?cat=8&feed=rss2','top');
}

That gives me exactly the same result as the previous code.

So how can I disable the 301 redirect for these functions?