weight of cast boolits not consistent....??????

[kevmc]

Having some issues with consistent weight of cast boolits.......

Lyman 429421-250K 4 cav.
Alloy is 50/50 Lyman #2 and PB
cast at 700* (thermometer), mold preheated on hotplate.
Most all boolits look good, nicely filled out..no wrinkles....not frosted....round... .4315 dia.
Visually, most all look good, but weight varies from 246 to 253....this from the middle of the pot (Lee 10# bottom pour)

They do seem to shoot well....and I know " if it ain't broke don't fix it........"
BUT, I'd like to see more consistent weights, ..(I'm somewhat anal retentive about such things!)
I'm new to casting boolits, trying to use same technique each time.

Tips for more consistency?????

[detox]

If pot or mould temperature varies alot, weights will change.

[detox]

Single cavity mould will be more consistant.

A sharp sprue plate cutter helps cut sprue even with boollit base.

Ladle pouring is very consistant IF you have good technigue.

650 - 675 pot temp should work

[kevmc]

I left the thermometer in the pot while casting...temp stayed pretty well from 680-710*......
mold temp??? I preheated the mold, poured 10 molds, then kept the next 10 pours to check weight with....
technique?? I'm opening the bottom pour fully, trying to put stream directly into cavity thru sprue hole.....

Sort by cavity to see if they match....???

[kevmc]

I'll try 650-675* tomorrow......
Maybe make a run of all one cavity to see if I can narrow down the issue, see if all cavities are same size.

[rintinglen]

It has happened that one or more cavities can be different from its confreres, but a more common cause is inconsistencies on the part of the caster. I find that as time goes by, my grip on the handles relaxes and the mold halves can spring apart slightly, not much, maybe only a thousandth of an inch, but enough to produce the kind of variance that you are describing. Try this. The next time you cast, set aside your first good cast, noting which boolit came from which cavity and do the same with your last cast. I guessing that the boolits from each cast will be pretty close one another, but the average of the first cast will be different than the last cast. And I also think the last one will be heavier than the first.

[HiVelocity]

I don't weigh mine right away. I check for flaws and rounded bases first. I cull out all the rejects. AFTER I lube and add gas checks, then I'll select 10 to weigh at random and see what I've got. You're right though, "If it isn't broke, don't fix it."

HV

[kevmc]

I checked the lightest of the bunch under a magnifying glass, couldn't find the missing lead anywhere!!!
Looked good on the outside, dimensions same as others......
That missing lead must be on the inside, a void somewhere, and probably due to technique I'm guessing.

[supv26]

On any of mine they do vary slightly. Tonight I weighed some of my .356 124 grain and my samples were running between 124 and 125. The heaviest one I sampled weighed 125.3.

[kevmc]

1 or 2 grains sounds good......I'm getting 6 - 6.5gr when casting .431 250's.

[David2011]

Are all of the corners sharp or are some rounded? Rounded corners will really affect weight. Are you casting at a steady rhythm? An uneven rhythm will cause variable results because te mold temp will vary. Mold temp is controlled by the pace at which you cast- not the temp of the melted alloy.

What is your alloy? If the tin content is marginal that affects the flow and wetting characteristics which in turn can cause variations in weight, expecially f the mold is at the bottom of its useful temperature range. Try casting a little faster and at a steady pace.

David

[bruce381]

run them frosty thats how I do and mine vary 1-2 grains at most from start to finish when humming along .5-1 max

[ddixie884]

Do you run an ample sprue?

[runfiverun]

did you look inside the boolit where the weight is missing from.
.
.






think about it.

[kevmc]

Corners all look good, even on the light ones, sq'd off nicely...bases full and sq.
Allooy is 50/50 #2/Pb
Running ample sprue....

"did you look inside the boolit where the weight is missing from."
Must bee a void....haven't cut any apart looking for bubbles tho...

[45-70 Chevroner]

If I were shooting bullseye competion I would worry about it, but for every day shooting that much weight difference is of no concern especially for pistol. If they look good they shoot.

[918v]

Try casting only one cavity and see if you still have that variance.

[prs]

I'm opening the bottom pour fully, trying to put stream directly into cavity thru sprue hole.....

I think I can give you a tip or two that will help. With what you say about using a consistent alloy temp and having a nicely pre-heated mold, and given the mold you are using is reasonably machined; I suspect the statement I quoted is your Huckleberry. Experiment with angled pouring and pour rates. Some molds encapsulate air if the rate is too high and the pour right down the center. I pour right next to the edge of the cavity and use a moderate pour rate. On multi cavity molds, I tend to pour close to the edge nearest to the next empty cavity and I slightly tilt the mound so that the cavities I have already filled are a little lower than the one I am working with. This technique allows me to fill both or all four or all six cavities without stopping the flow, it lets any over flow of the sprue puddle collect back toward already filled cavities and NOT contaminate the next cavity, the alloy flows into the mold with a slight swirl and there is time for any air to escape via the provided lines cut into the mold or out the top of the sprue plates. Not all molds "like" the same exact technique; why, I dunno, just the way it is. Some like the pour from the side of the cavity, others like it a bit toward center, just try it and see what your mold "likes". Do use a generous sprue puddle and do keep your repetition rate high enough so that the alloy remains liquid in the cavity for a couple of seconds. Some of my Lee 6 cavity molds "like" me to sort of shake or vibrate them as I make the pour, as if I have Parkinson's.

Another tip for consistency, consider a PID controller.

prs

[Jim..47]

Please excuse my side questions

Are all of the corners sharp or are some rounded? Rounded corners will really affect weight. Are you casting at a steady rhythm? An uneven rhythm will cause variable results because te mold temp will vary. Mold temp is controlled by the pace at which you cast- not the temp of the melted alloy.

What is your alloy? If the tin content is marginal that affects the flow and wetting characteristics which in turn can cause variations in weight, expecially f the mold is at the bottom of its useful temperature range. Try casting a little faster and at a steady pace.

David

I tend to cast on the hot side, many of my bullets are frosted. Other then looks, for punching paper or cans, does this hurt anything? (I will be getting a thermometer by the end of summer.)

run them frosty thats how I do and mine vary 1-2 grains at most from start to finish when humming along .5-1 max

This is what I do, as explained above. I know that you are more likely to get bullets that will come apart on impact, but does it hurt anything else.

Also, what do you all of you guys do to salvage tin in the bullets? Do you have a dedicated backstop for tin added bullets or just buy more, or are you able to find scrap tin from some source?
Thanks

[Jim..47]

Mr. PRS, what is a pid controller?