[Floreos]

Here is a definitive answer for you. At least accuracy wise.

You will not see any more accuracy/consistency benefit after 450mm length. This is kind of the sweet spot that allows your spin from your hop up to stabilize but not so much as to start having irregularity down the barrel.

That being said if you need a smaller one for cqb you will probably fine.

Edit: if you're an aeg player you will need to match your cylinder volume. (I'm not an aeg player so I'm uneducated about the subject.)