I cast some 309-170 and 459-500-3R last week out of Lyman #2 alloy. Each design and batch has its own interesting quirks and issues.
1. For 459-500-3R, this is quite a hard alloy for the application of this mold. My bullets are dropping out at about .460. If my bore is at about .458, could I still choose a load developing low pressure and could still avoid leading?
After all, we are looking for a certain fit in the bore that minimizes gas cutting right? So technically, if the bullet's diameter is close to where you want to bump it, then bump it slightly with pressure, do you achieve a similar effect with a softer alloy and smaller diameter to maximize velocity and eliminate cutting?
2. Same with the .309, these bullets are dropping out at .309 or below, could I use a higher pressure and velocity load to bump the tail to a larger diameter needed to seal the bore, even with a gas check?
Am I asking the right questions? My guess is that these are the dynamics we are trying to mimic in our load development to control velocity and leading but I am not sure; its like we are just controlling the amount we bump our bullets to seal the bore.
Or for short, could these two situations achieve a similar effect: small, soft bullet bumped a lot or slightly larger harder bullet bumped a little?