Jamison Brass

[bruce moulds]

or get an rcbs file trim die.
you can hacksaw off the excess, and tidy up with a file fairly pronto.
deburr inside the case while in the die.
set the die a bit long to start, as these dies produce cases about 0.010" shorter than spec for liturgation reasons.
i usually adjust the die down to the shellholder, lock the ring, and then put a fair ammount of skip's shims under the lockring.
form a case, measure it, and then remove the required no of 0.001" of shims for the correct length.
i have formed quite a few 45/2.4" pp adaptors from norma 31/4 brass like this.
keep safe,
bruce.