04 December 2019
First of all, is your 40-65 a "current or recently built rifle?
If it is it will probably be a 0.408-0.410 groove dia. Those "403XXX" molds you mentioned will
be too small in diameter for your bore, even tho, with BP, and cast very soft they would bump up
and maybe shoot decently for hunting.
So, the 38-40 bullets at 0.401" or so will also be too small in diameter as well as really too light at 180 gr or so. Almost Like shooting round balls.
Then, your 41 mag pistol bullets at 0.410 may work very well for you.
Last year I picked up a Lyman 410459, 220 gr plain base Keith semi wad mold that I am looking at
trying for a lighter load for my 40-65- in my case, mainly for offhand close range
practice understudy for my BPCR match shooting. There is also the 410610 version which is a gas check semiwadcutter design.
The original bullet weight in 40-65 was 265 gr. Maybe NOE or Accurate molds would have a flat nose 0.410 diameter bullet in that 265 to 300 gr weight
Just curious, are you looking at BP loading or smokeless?