weight difference when water dropping?

[cricco]

Greeting folks. I just finished casting some 9mm boolits with my Lee 90465. This mold drops consistant 126 grain boolits. Tonight I tried water dropping them for the first time, mostly because I needed an excuse to cast some boolits. What I found was that these water dropped boolits were consistantly 124 grains. Also, my last batch of non water dropped were sized at .358. These were .356. Can anyone explain the weight difference?

[lwknight]

I can tell you that it had nothing to do with water dropping as far as the weight goes for sure.
I think you have an alloy difference. I have a mold that casts .429 with tin/lead and .431 with high antimony alloy.

[JSnover]

Your alloy or your mold temp changed.

[HangFireW8]

Greeting folks. I just finished casting some 9mm boolits with my Lee 90465. This mold drops consistant 126 grain boolits. Tonight I tried water dropping them for the first time, mostly because I needed an excuse to cast some boolits. What I found was that these water dropped boolits were consistantly 124 grains. Also, my last batch of non water dropped were sized at .358. These were .356. Can anyone explain the weight difference?

The thinner boolits weigh less.

The thicker boolits weigh more.

-HF

[fredj338]

Your alloy or your mold temp changed.

I don't think mold temp even causes wt variations on the average. Even w/ larger 340gr 45/70 bullets, I don't see any weught variations when water dropping vs air cooling.

[mpmarty]

Whatever the boolit weighs coming out of the mold is what it will weigh coming out of the water! Lead doesn't dissolve in water.

[tommygirlMT]

Water dropping in and of itself did not make the change --- but it is a big part of it. When water dropping you can run your mold at a brisker pace.

This prisker pace is what caused your variation. You don't have to wait as long to drop the boolit compared to air cooling where you are worried about dents due to dropping too soon. Faster pace means hotter mold temp. Hotter mold temp means more boolit shrinkage during cooling and reduced weight.

At least that is my theory from what you stated in your OP.

[cricco]

Water dropping in and of itself did not make the change --- but it is a big part of it. When water dropping you can run your mold at a brisker pace.

This prisker pace is what caused your variation. You don't have to wait as long to drop the boolit compared to air cooling where you are worried about dents due to dropping too soon. Faster pace means hotter mold temp. Hotter mold temp means more boolit shrinkage during cooling and reduced weight.

At least that is my theory from what you stated in your OP.

This makes sense! Thank you.