First casting, wide weight variation

[sigep749]

Cast my fist boolits today, Lee pro pot and 158gr 6 cavity TL Lee mold. Look pretty good, only one batch frosted, no wrinkles. My concern is the variation in weight. The first 10 I grabbed to weigh range from 163 to 169gr. Should I be concerned? Will temperature variations cause that much swing in weight?

[RobS]

Mold temps can bring some variance like what you are seeing and with it being a Lee mold as well you could likely be looking at how things are. Next time you cast go ahead and drop them as a group from the mold and check the cavity to cavity variance. Then do a drop as the mold is up to temperature, then again in the middle of the session and then again at the end to see what is going on with your casting session. After this you'll know if it has to do with your mold temp or if it's the mold giving you an additional variance from cavity to cavity. I wouldn't be too concerned about a 6 grain difference regards to safety and you'll likely not see the difference on the target either.

[Cherokee]

Variance are normal to me. Casting the Lee 358-158 conventional design today, weight ranged from 159 to 162 using range lead. The target will never know the difference, but my OCD would like for them to all weigh the same.

[Mk42gunner]

As you progress in the madness, you will find that Lee molds like to be run fast and hot. As you gain more experience, your variation should go down, due to becoming more consistent in how you fill the mold.

If your boolits look good in your initial casting session, I wouldn't worry too much.

Also remember that rejects are really just small ingots, waiting for the next time you cast.

Robert

[hickfu]

Flow control and keeping the temp the same worked for me. My 430gr .460's used to come out with a 13gr difference from light to heavy. I slowed my flow down to keep air from being trapped and kept my temp right at 750 (holding the empty mold in front of a fan for 5 seconds to keep it from getting too hot) and now they are all within 1 grain of each other, most are within 1/2 grain. Different cavities can also drop at different weights so a good way to check is pour from 1 cavity, then the next and so on for a few pours (keeping the boolits from each cavity all together) and then weigh them.

Doc

[MtGun44]

163 to 169 has a midpoint of 166. This is +/-3 grains, which is +/-1.8%. This is not
bad at all for pistol boolits. Certainly tighter weight control is possible, and perhaps for
long range rifle matches you would really see a difference, but for pistol ammo, for any
but THE most demanding long range shooting, I'm sure you will be fine.

Try this experiment. Sort out 10 at the midpoint (166) and 10 that have 5 light and 5 heavy.
Load the same and shoot a 5 shot group with the 166s, then a 5 shot group with
the lights. Then go back on the first 5 shot 166 target and put the remaining 5 166s
into it, then the same for the remaining 5 heavies into the previous lights target.

The point is to average out your shooting errors and any change in ability to focus over the
twenty shots fairly amoung the two groups. My bet is that the differences will be
undetectable.

Bill

[williamwaco]

I think that is an acceptable range.

The range will tighten as you practice more.


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[Jailer]

Inconsistent casting tempo and temperature variation are what cause the weight difference. Once you find a good "cadence" the gap will narrow.

Keep at it you'll get there. In the mean time, shoot em and enjoy.