Although the barrel length of the No5 is 100 mm shorter than the No4, with some half decent optics (that can handle the recoil forces) and some Mk8 .303 boat tail ammunition, you should be able to get reasonable groupings out to 800 metres @ around 8 to 12 inches. You should be able to get somewhere near to the sniper performance of the M25 system with the No5 being couple of lbs lighter than this specialist SOCOM weapon.

Happy shooting.