According to Down Range TV, FNH is
introducing the conversion kit for FN SPR rifles.
It is called Tactical Box Magazine (TBM) Conversion Kit and it is a more or less a drop-in conversion kit. It comes with a 10-round magazine, a 5-round magazine, new actions screws.
It can be purchased from FNH E-store or
Midway USA
Price(MSRP): $449(
FNH E-store) (Midway sells it for $399)
From: DownRange TV