Gearing up to start casting again. Wanting to get my sizing dies and things ordered. So I ask this....is it always necessary to slug new barrels? Wouldn't they be pretty much all be to spec from the factory in proper size? Always though sugging needed to be done with barrels that have had thousands of rounds through them and had some wear. Reading here it sounds like everybody does it for every gun they cast for. When I was loading and casting before, I admit I never slugged any of the 5 guns I casted for. Just went with one over diameter sizing dies from spec bore diameters or just shot unsized as cast if it drop spec size from the mould. Never noticed any issues with leading or accuracy then. Plan to do a bit more this time and will slug barrels in the next few days. Doing the following loads this time around starting off... 9mm Luger, 45/70, 357 Mag (rifle and revolver), 44 Mag (rifle and revolver), and likely 223 (plinking loads). A few more calibers will be added, but this is the starting line up.