Will Reminton 700 barrels fit in a 721? I didn't know if the threading, etc was the same. I am having a really hard time finding a 7x57 mauser barrel for the 721 that won't break my bank account.

Go to this site and ask your question. They've been very good with this kind of technical information. They also have barrels.

http://www.brownells.com/aspx/NS/GunTech/submitquestion.aspx