"hard cast bullets" is nebulous. Does not indicate how hard. Try them and see if you have undue leading (the proof in the pudding), adjust your load accordingly. Vague, but sage-sounding advice from another shooter is usually worth exactly what it costs.
Sometimes you get what you pay for, sometimes you only pay more for what you get.
Three shots are not a "group"...they are a "few".
If the Bible is the literal, infallible, unerring word of God...where are all those witches I am supposed to kill?