As I remember, the SPR is warranted for life, but I don't know if the warranty follows the rifle if it's sold. If you're not 100% sure about going with the CDI bottom metal, why not give FN customer service a call tomorrow and ask? Even if you don't get through right away, they'll get back to you in very short order. Last time I had to call them, I think I was on the phone for 15 minutes or less.
NRA Life Member since January 2009