I have my thoughts , and here they are I own many slug guns and probably 50 to 60 molds , and I also have spare barrels , If I have a super accurate gun I tailor my ammo to it ,
example if it is unchoked barrel say and it is .300 then I will want a swagged or casted slug .3005 . for best accuracy if this is my bore , and I may modify a few molds to make an exact cast or swag ammo where it needs NO sizing , so I thrive to get a die or mold exact ,
Now I have a few slugs in .22 250 and 257 and I have some guns I just like so yes I also will buy rifle blanks to tailor to my ammo , so my answer is I do both and found this best .I have not found accuracy I can get from a store bought slug , I mean some are shoot-able but for say ,hunting coyotes with my 22 and 30 cal , My ammo is king for me ,as I like solid heavier slugs bettor for this ,
It is like anything else you need to start with a good design slug proven by you to move forward or a gun and power to shoot a certain slug then match it that way , I have casted and swaged now for decades and I love about 6 molds I own out of geeze a hundred , so for me to love it , I go threw alot , I wont waste time on poor quality barrels or poorly designed slugs .