Yup, old, old business. The forend controls how tight the barrel is when the action is open, it also affects accuracy, depending on how tight it fits. If the barrel is tight with no wiggle when the action is closed without the forend on, there's no serious problem to worry about, if it's loose, you need a new barrel or it needs to be shimmed. Wood forends are easy to tighten by adding shims between the spacer and forend or bedding the spacer, synthetic forends aren't so easy cuz they have no spacer. For a wood forend, see forend work by just bill in the FAQs.
Tim
