Remington made some Light Varmint rifles in 221 FB. Might be a possibility for an action.
I did a 221 FB on a 223 40X action and it was a nice gun.
I'd think one of the Score HI aluminum single shot loading blocks would also work with the FB on a standard 700 action.
Good luck.
A. Weldy
I have several 221 FBs and also 221FB in 700 LVSF. The Remington 700 fireball actions use a slightly different magazine spring and follower dimension than the 223's and also the location of the ejector on the bolt is positioned differently. Many folks report some problems with extraction/ejection when they convert a 700 .223 action to a fireball length use. There is quite a bit of additional info on saubier.com about all this. Don
Horror of horrors but you can also lick the problem by converting to a Sako extractor.