There are a small number of clamp blocks with the holes spaced wider than the threaded inserts in the rifle mount. These blocks are for the shotgun mounts. If you received one of these longer clamp blocks with your rifle mount, we will exchange it with you ASAP. Just contact us at info@fmsaccessories.com or call at 201-264-8365 to arrange an exchange. We apologize for the inconvenience.