Loose when open isn't important, the rifle can be fired without the forend, so being loose when open isn't a big deal. The forend controls how it fits when open, it's an easy fix to tighten on a wood forend by adding a shim between the spacer and the forend, not so easy on a synthetic forend tho, see
Forend Fit in the FAQs sticky above, best place to look when you have a question.
Tim