Much cheaper option.
The standard bore for .218 Bee was .224. At the same time, you could have a rechambered .22 RF. .22 RF bore is .222.
[You can cast/measure your bore with garden sulfur (melt outdoors. Pour like wax. If it catches fire, you got it too hot and IT STINKS). Plug the barrel. Pour in the molten sulfur. GENTLY push the plug out. Measure with mike. It is brittle and will not take rough handling.]
OR Then, you can buy a "ring die" with which to reduce the bullet diameter to whatever you choose. (Purchase from Corbins.com, rceco.com, ch4d.com, or any machine shop...) Shove a bullet you like thru and it comes out slighly smaller and more suited to your purpose.
Both brothers, Dave and Rich, have books on their web sites (swage.com and rceco.com) that discuss ring dies. Read and/or download before making a decision that will cost money.
OR you could buy dies with which to make your own bullets. Using fired rimfire cases is legendary and the basis of firms like Horandy/Speer (who worked together in Lincoln Ne briefly)... Dies and a large reloading press will give you whatever you want.
Having the rifling recut, possible, but I don't even want to guess the price. HIGH. LUCK