Metal rubbing on your lands and groves from a cleaning rod and patch jag and patch loop can damage the lands and groves and the crown of the barrel over time. A guide prevents the rod from touching the rifling. Do you need it? That is up to you. Problem is, if it is possible, it is best to clean a barrel from the breech end and I have never sen a bore guide that will fit in the breesh end of the barrel. Not saying there aren't any, just that I have never seen any.