My 2 cents. I don't think you need it unless you just want a certain style rail the factory type does not have, like a Picatinny style. With that being said, I have pretty much made it a habit to use a 20 MOA rail on all my centerfire rifles. Do I need it and will ever need it? Probably never will. But, I have never found it to be an issue with dialing the scope down a bit due to the extra elevation. It is there if I need it and may be more appealing to someone if I sell the rifle with the mount.

But, for a rimfire, I just don't see the need. But, if you went with a new rail, I see no harm in a MOA rail.