Rewrite Attachment Url's

add_filter('pre_get_posts', 'diiish_build_attachment_query');

function diiish_build_attachment_query( $query ){

  if( !is_admin() ){
		global $wp;

		if( preg_match( '/^media\/(.*)/', $wp->request ) ) {
	
				$req = explode( '/', $wp->request );
				$id = $req[1];
				$query->set('name', '');
				$query->set('error', '');
				$query->set('post_type', 'attachment');
				$query->set('is_attachment', true );
				$query->set('custom_attachment_url', $id );
				$query->is_attachment = true;
				$query->is_single = false;
				$query->is_singular = false;
				
		}

	}
	return $query;

}

if( !is_admin() ){
	add_filter( 'posts_request', 'diiish_post_select' );
}

function diiish_post_select( $req ){

	
	global $wp_query;

	if( isset( $wp_query->query_vars['custom_attachment_url'] ) ){
		$id = $wp_query->query_vars['custom_attachment_url'];
		return "SELECT   wp_posts.* FROM wp_posts  WHERE 1=1  AND wp_posts.ID = ".$id." AND wp_posts.post_type = 'attachment'  ORDER BY wp_posts.post_date DESC";
	}

	return $req;

}


add_action( 'template_redirect', 'diiish_redirect_template' );

function diiish_redirect_template(){

	if( !is_admin() ){
		global $wp_query;

		if( isset( $wp_query->query_vars['custom_attachment_url'] ) ){
			$id = $wp_query->query_vars['custom_attachment_url'];
	
			if( isset( $wp_query->post ) ){
	
				$mime = $wp_query->post->post_mime_type;
				$mime = explode( '/', $mime );
				$template = $mime[0].'.php';
	
    			locate_template( array( $template, 'attachment.php', 'single.php', 'index.php' ), true );
    			die();
	
			}
	
		}
	}

}

I changed the 'wp' action to 'template_redirect'. This didn't work before but by eleminating a few attachment_id variables in pre_get_posts and get in our own variable; it now works without 'having to prevent a redirect'. it's more streamlined.