Cylinder bore up kits

[Jbone 11 11]

I want to install a longer inner/outer barrel from a 285mm barrel to 363mm.
I've been reading a lot about upgrading the cylinder as well when changing barrel length, but am unsure as to what exactly I need.

I've got a M4CQB (orig. a Royal, but with a JG metal body and upgraded internals) and am looking at element M4 or M16 bore up kits, but am unsure which is the right one? I've also read that a upgraded spring is necessary... again, not sure what I need if anything.
Any advice on what makes are worth looking at is welcome as well.

Tx!
J

[The Saint]

You don't need a bore-up kit unless your inner barrel exceeds 600mm.

You might need to change the cylinder, but the only difference to your old cylinder will be where the hole on the side is placed. Depending on where that hole currently is, you might not need to change the cylinder.