Inconsistent weight

RLD4570

New Member
I’m casting a 535gr 45 cal bullet for bpcr and after getting inconsistencies in weight I noticed the grease band on one side on some are rounded. Is this due to air?
 

Brad

Benevolent Overlord and site owner
Staff member
What alloy? Bottom pour or ladle?
Got any photos of the bullet and the flaw?
 

Rick

Moderator
Staff member
My guess would be due to mold temp rather than air. How much inconsistency in weight? Something like one grain in 535 gr is a very small percentage of the whole. A one grain variation in a 45 gr 22 bullet is a much larger percentage of the whole and would have a larger impact on accuracy.
 

Brad

Benevolent Overlord and site owner
Staff member
Photos of the bullet flaw and knowing the alloy will help diagnose what Rick mentioned. Could be a mould too hot or too cold.
 

Brad

Benevolent Overlord and site owner
Staff member
532 to 535 isn't that bad. You are well under 1%.
If I had to guess I would say mould is cool. How long for the sprue to set up?
Try a #2 Rowell ladle and I bet it gets way better.
 

Rick

Moderator
Staff member
532 to 535 isn't that bad. You are well under 1%.
If I had to guess I would say mould is cool. How long for the sprue to set up?
Try a #2 Rowell ladle and I bet it gets way better.

Yep, that Lyman just doesn't pour enough heat/lead for a 535 gr bullet in my opinion. I use the Rowell #2 almost exclusively and on far smaller bullets than your pouring. Pick up a #2 and see if your life doesn't get easier. As for the weight your actually holding around a half of one percent of total bullet weight variation. Pretty good especially considering the tiny ladle.

When your filling the cavities don't think of it as pouring lead. Think of it as pouring heat, heat the mold needs to perform at it's best.
 

Brad

Benevolent Overlord and site owner
Staff member
Ditto, cold mould.
The bigger ladle will make a huge difference. By pouring more often over the mould, even once filled, you increase heat transfer.
I took a while to listen to Rick on the #2 Rowell but once I did I haven't looked back.
 

Ian

Notorious member
I third the #2 Rowell ladle. You can actually cast great bullets with a bottom pour, IF you keep the mould hot enough. The big advantage of the ladle is being able to keep the sprue washed out until the bullet freezes so that you don't get base voids. The Lyman ladle is ok for 150 grain or smaller two-cavity moulds or 200 or so single cavity, but beyond that, larger ladles do much better.
 

Rick

Moderator
Staff member
RLD, keep in mind as your casting improves with experience that mold temperature is the leading cause of casting problems. That's not to say crank up the pot temp, with your alloy somewhere between 700 and 750 degrees is more than needed. Pre-heat your mold and cast at a faster pace to increase mold temp. Don't inspect your bullets as you cast, while your doing that the mold is cooling even more. If the mold gets too hot you'll see it quickly and slow your pace a bit.

The reason your bullets look like they do in the picture is because the mold temp is too far below the freeze temp of the alloy, the alloy flowing into the mold is actually freezing against the mold before it has a chance to properly fill out all the corners.
 
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RLD4570

New Member
I failed to mention I run the temperature at 750 pid controlled Lee pro.
Thanks and I’m going to order a Rowell #2
 

Brad

Benevolent Overlord and site owner
Staff member
Do some measuring and make sure the ladle will fit in your pot.
 

fiver

Well-Known Member
and nevermind the pot temp [which is too high]
casting is ALL ABOUT MOLD TEMPERATURE. [yeah I was shouting LOL]
my first casting pot wouldn't get hot enough to melt pure lead.
I learned to ladle cast straight WW alloy from that pot.

one other thing to look at on that side of the mold is the venting and making absolutely positive it is clean.
I had a lyman 375449 that would give me rounded bands like that even with it being about 3* from frosting over to a nearly white bullet.
I had to scrape/brush/scrub/plead and whine and gently scribe the vent lines from the cavity's to the mold edges with an X-acto blade [rinse and repeat a few times] with the thing to make it do what I wanted.
 

fiver

Well-Known Member
your tin will start to oxidize quickly at 750.
my money would be on most here using somewhere around 700.
[I'm usually around 685 when I get things up and running smoothly, I don't use a PID or hot plate]

I bet Rick and a few others use about 100-110 F over the melt temp of the alloy as a guide.
 
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