Use this snippet to change the bundled items column count when using the 'Grid' Layout option

woocommerce-bundles-product-grid-layout-columns.php

<?php
/**
 * Plugin Name: WooCommerce Product Bundles - Bundled Items Grid Layout column count
 * Plugin URI: http://woocommerce.com/products/product-bundles/
 * Description: Use this snippet to change the bundled items column count when using the 'Grid' Layout option.
 * Version: 1.0
 * Author: SomewhereWarm
 * Author URI: http://somewherewarm.gr/
 * Developer: Jason Kytros
 *
 *
 * Copyright: © 2018 Jason Kytros (jask@somewherewarm.gr).
 * License: GNU General Public License v3.0
 * License URI: http://www.gnu.org/licenses/gpl-3.0.html
 */

add_filter( 'woocommerce_bundled_items_grid_layout_columns', 'wc_pb_grid_layout_change_number_of_columns', 10, 2 );

function wc_pb_grid_layout_change_number_of_columns( $columns, $bundle ) {
	return 4;
}

Excellent stuff, thanks.

This works for desktop. But not looks good on mobile. It would be great if it is possible to extend to different screen sizes.