Why am I getting this ?

[vrh]

I use an RCBS 95 -SP bullet mold. My bullets have been weighing 95 grains fresh from the mold.
Started using a new batch of lead and now I'm casting at 98 grains. What happened to make the
bullet weight change? Anyway to regulate the weight of the lead to maintain a
more constant weight of cast bullets?

[DAFzipper]

Composition of alloy must be a little different. Probably has more PB causing weight increase.

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[GhostHawk]

Tin and Antimony are both lighter than lead. So if you had for example an alloy that was 4% ant, and 2% tin you have 94% lead.

Now if you drop down to 2% ant and 1 $ tin you have 97% lead which is going to weigh more than the other mix per bullet.

That is why a lot of people when they smelt down wheel weights, add a fair amount of pure lead, do so in big batch's. So once the whole batch is melted, the resulting alloy will be consistent from one ingot to the next. As they are all part of the same batch.

[DHDeal]

Nailed it he did. The change in alloy is where the change came from. I've went from straight COWW to Hardcast and pure lead 50%-50% (real close to the same hardness I do believe) and noted a 3 grain difference. I suspect my 20/1 alloy would be even heavier than either of the other alloys.

As others will tell you, the way to get a very consistent weight/size bullet, start with a very consistent alloy made in large batches.

I probably am not the only one with many different alloys for different purposes. I usually pick one and stay with it for that bullet/caliber combo.