Explanation of changes when alloys are added - don't get it

[chutestrate]

This is from a link by rotometals. I'm new to casting, and I don't get the whole alloy recipe concepts. Once I test my bullet hardness I'll have to decide what I want to do with it. I'm still struggling with how to increase/decrease hardness, when to do it, what to use, etc. The LASC.US site is probably a great resource, but right now it's over my head.

My Lee manual is ok for reloading data, but not getting much for casting guidance either.

Weight and Size differences. As the percentages of the alloys in a melt change other changes occur in addition to the weight of the bullet. In general the higher the percentage of Sb the larger the as cast diameter of the bullet and the larger the diameter of the bullet the more increase there is. In other words a 45 caliber bullet will show more of an increase than a .308" caliber bullet (table 3). In addition, the alloy percentages have a direct effect on the final sized diameter (table 1). I imagine the sizer die makers get daily phone calls from customers complaining (as an example) that their .309" die sizes to .3084" and not .309". If you change the alloy the weight, as cast diameter, shrinkage, sized diameter and BHN all change. Higher Sb percentages also result in less shrinkage as the bullet cools and it's possible for this simple fact to result in bullets that are a bit tougher to get to fall from the mold (table 2). From the tables it can also be seen that in reverse the softer the alloy (less Sb) and the larger the diameter of the bullet that more shrinkage will occur.

[jsizemore]

All the "technical stuff" is to give you the tools to find what works in your gun for the job at hand. What works shooting targets at 50 yards at 900fps probably won't work at 200 yards at 2200 fps on something with big bones you intend to eat. The idea is to shoot it in you gun and evaluate your results. If it works, great. If not, others past experience can guide you in the right direction.
It takes a little time to discover just what you don't know. Wait til you get a little further down the road. Lots of fun.

[fryboy]

i'm not really sure of your question (ing)not even sure that i'm the guy to help but ...
mold makers use a set ( to them ) alloy for deciding upon the molds size , sometimes it mirrors our use sometimes not , as a newbie i just made and shot , my only help was lyman's manuals which while excellent reference sometimes they leave a bit to be desired but they did give one a book that they could study etc at their leisure , of the known and most widely used alloys the softest and the heaviest ( per same mold casting ) is lead , it's heaviest because it's the densest , as you have noted the same casting with various ingredients produce varied results , antimony is the lightest and hardest of alloy additives that we use with tin being in the middle , varying amounts in the alloy produce different results , the lead being the densest and softest will have less "springback" after sizing or resistance to sizing if you will , also because it's the softest it wont resist the forces from loading and firing ( tho it does expand like a dream - even at muzzle loading velocities ) while we can add ingredients to make the boolits larger the primary reason is harder and tougher , solid pewter boolits are way lighter than lead ones ( kind of cost prohibitive as well ...) tin is a bit more malleable than antimony which by it's self would prolly shatter or break , by combining these 3 we get some great alloys with perhaps some of the best from all , the charts that lyman and the lasc site have tell us kind of what to expect by this , it's generally accepted that alot of tin isnt needed , ye olde lyman manual states any more than 10% is a waste ( we have some guys - myself included ) who think 4% is a waste ( i do make a true lyman lino #2 alloy tho )
we as casters and handloaders try to do it on the cheap , things like getting by with as little of tin as possible etc , the real question is what kind of alloy do you have and what do you want to do with it ?

[fredj338]

Decide what you want your bullets to do. That will determine the alloy you want to shoot for. You can get perfect results using ww alloy for all your handgun needs. Add some lino for rifle bullet vel over 1500fps. It's not much more diff than that for most shooters IMO, but I am not looking for extreme accuracy from a rifle either. The 45-70 is the only rifle that gets lead bullets in my little arsenal.