The only time I have fired a .25 was six rounds through a Saxby-Palmer Orion revolver, which had been up-bored (by a gunsmith who will remain nameless) to .25 with a brass barrel liner. It was doing 9 fpe and was very accurate, like a rimfire at 10 meters. Gave a very satisfying kick.
Is it true that you only have to hit the faceplate to knock down HFT targets with one?