Tinker:
Everyone I know uses the ISSF 25m/50m Pistol Target or equivalent. It has a 20cm or 8-inch black bulls-eye on a large white target about 55cm square, but an A3 copy of the middle part works fine. I re-use club targets shot with .22 pistols, as the holes I make are usually easily distinguished from a .22 impact! This one has a couple of rights and lefts from a Wm Griffiths 12-bore:

The Big Game Rifle Club also use this target for most of its matches in State and National Championships.

It is perfect for a round bead front sight at 50 and 100 yards.