How does this happen?

[JWFilips]

This has bugged me for a number of years I have had it show up from time to time and since It showed up today ( to what I feel is an extreme) in my cast bullets I figured I would throw the question out

First off I bottom pour out of a Lee 20 lb pot and keep it at about 715 deg
Today I cast up about 75 bullets Once cool, weighed them in to .1 gr increments Had about 95 % fall into a .4 grain range Which I'm happy with.
Sure there were a few lighter and a few heavier that I toss back into the pot but I had 3 of them come out 2.5 grain heavier! How does this happen? I find that very strange
Jim

 

[fiver]

and why only three?
if it was 4 and a 2 cavity mold I could see 2 pours where the mold wasn't quite closed.

 

[freebullet]

Sprue plate or closure issue.

Only takes a tiny smear of alloy under the plate.

 

[JWFilips]

Forgot to mention Only casting one cavity If not quite closed wouldn't I see fins?

 

[Ian]

Jim, you described 95% of how my casting is done. Measure the heavy bullets, either the mould wasn't closed all the way or the sprue plate rode up on top as the others wrote. No, you won't see fins with only a few grain weight difference.

 

[RicinYakima]

What Ian Said!

 

[JonB]

I had a couple troublesome molds, although as I look back on it, it may have been partially due to an inexperienced operator? LOL.
But while casting with those molds, If I had a difficult time keeping the temp of the mold hot enough, I get the sprue bump...that's a extended bump. I suspect my issue was also accentuated by a dull sprue plate cutting edge and a fairly loose sprue plate where the washer would allow the plate to ride up when cutting the sprue on a cooler bullet. I never measured them, to find out how much heavier they were?

 

[JWFilips]

Just wanted to be sure it wasn't a gravitational abnormality!
I wanted to be sure it hadn't been something to do with my cadence or pour height. In the past year I have found that I'm becoming much more consistent in my casting which really helps my confidence. My casting session bullets are getting tighter and tighter in consistent weight range.
The sprue plate indeed was a bit looser then I usually work with. & I was casting hollow points with knob & pin, so I can see some areas there ( Now that you guys mention them) that could explain it. Good thing it was only 3 bullets. Tonight I'm going to dig them out of the pot and measure them
Thanks

 

[Cherokee]

IIRC, most of the "overweight" CB's I see in my lots have a large bump on the base usually due to the poor cut off of the sprue.

 

[KHornet]

Ya Jim, agree with Ian!

 

[KHornet]

On the other hand, I have a couple of molds that I know are haunted!
Over the years, I have had a few cases of 2 or more grains lite, and when
I cut them open I found voids. Sort of like the lettering on the pregnant
ladies sweat shirt: "Poo Poo Occurs"!

 

[Brad]

Read Veral's book and this why he doesn't get excited about weighing bullets.
A bullet where the mould was slightly open would be a little larger and therefore heavier. What if those had large enough cavities within them to make them weigh in the normal range? They won't shoot into the same group quite possibly.

Sort by diameter, then weight and see what you get.

If it was easy it wouldn't be fun, would it?

 

[Ian]

Yup. I always sort my "must be perfect" bullets with a micrometer, and check the noses with a hole gauge if they're tapered. Then weight sort for the odd one-grain-light one that "makes grown men cry" as Beagle used to say.

 

[quicksylver]

Jim ...the good news here is that your bullets are coming out fairly consistent and you are doing do diligence on your sorting...good for you !

You didn't mention what bullets you were casting..so 2.5 grains on a 45 colt 255 grainer wouldn't be all that far off..on a 180 30 cal..it would perk my interest more..

I do get those occasionally when casting large batches of 200 grain 30 cals...beautiful looking bullets to the eye..but the scale says they are not from the same herd..happens maybe .01% of the time....actually can happen on either end of the weight range.....

Do I do anything different to try and keep it from happening ?..NO..I just ponder it like I do when I try and figure out how my wife knows exactly what I'm up too..

It's the half empty /half full deal ...look at all the good ones you get.!!

Heck ...I am still trying to figure out why my nose riders like the 299 have a "waist"..example full nose diameter say .302..half way to first driving band it will measure less ..then right at the band it will be .302 again....sexy....

 

[Ian]

Heck ...I am still trying to figure out why my nose riders like the 299 have a "waist"..example full nose diameter say .302..half way to first driving band it will measure less ..then right at the band it will be .302 again....sexy....

Dan from Mountain Molds wrote a little article on his site about "shrunken bullet syndrome", which is exactly what you describe. Worth a read.

 

[JWFilips]

OK ,
I'm calling this an open mould problem because those 3 are larger! I can't imagine how that happened but it did.

As to Nose riders. I recently cast a bunch with one of Ben's mould a Lyman 311291 The bands and bases matched his measurement but my noses are smaller?
Now that bugs me! (I know Ben ladle pours & I bottom pour)

 

[RicinYakima]

There are several areas to investigate: a dot of lead on the face, usually works there from being splashed from cutting sprue over the pot if ladle pouring, a piece of lead from the sprue breaking off and being caught when closing the mould, a splash of lead on the joint of the handle, or failing to grip the handles with the same tension each time. These are all human faults, and not cause for alarm.

 

[Brad]

Jim, it happens all the time. We often don't notice it. Ever notice that every now and then you have a few bullets that seem a little harder to size? Now you know why.

This is all part of the learning experience. Now you have some things to look at and help identify a possible cause.

 

[quicksylver]

a dot of lead on the face, usually works there from being splashed from cutting sprue over the pot if ladle pouring,

??????...Ok...I am in definite need of higher education here.....I thought that while casting no materials outside of flux should be introduced to the alloy including the sprue ...UNLESS YOU WERE IMEITATLY REFLUXING.....plus I would think that dropping sprue into the pot would affect alloy temp.....or does that just apply to bottom pouring?

Rattle my world please...Dan

 

[Brad]

Many cut the sprue over the pot and drop it back in. As for temp, yes it is a bit cooler than the melt. It is not cold by any means and will drop the temp little. How much does your pot cool if you drop in a single cold 300 gr bullet?
Fluxing isn't that big a deal. You will, over time, get more dross formation on the surface do to oxides that formwed on the surface of the cooling sprue. Again, not a huge deal.

This will give Rick hives but I have been known to add ingots to the pot as I cast. Generally only done when casting plinking type handgun bullets in large numbers. The PID does show a temp drop of up to 50° F with each addition but quality stays sufficient for my needs.