I think the 527 American is the only model still available in .221.
The FS is currently only available in .222, .223, & Hornet.
All of the 527 models are great little units. Good barrels, an excellent adjustable trigger setup, and very nice wood.
The only thing I find quirky about em is the "backwards" safety lever (back is fire, forward is safe). That does take some getting used to.
I agree that the .221 would be a good little "light" centerfire varmint round for a rifle. Just the thing to fill the gap between the Hornet and the .222/.223.
Personally, I'd like to get that cartridge in a 14" XP someday...I think the 10" on the original plastic-stocked XP is a little to short to really get the potential of the .221.