Weighing bullets

[Mike W1]

Been weighing some more #452374 bullets. I have 2 different DC moulds and they're roughly 10 grains heavier out of one mould than the other. The one I was fiddling with today seems to average about 0.5 grains difference between the 2 cavities. Frankly with the plinking I do it doesn't make any difference.

What go me thinking today was the variables I can't really control and how much they'd affect the finished bullets. I'm not finicky enough to go the extremes and get the results one fellow on here gets and not sure I'd get them all into a 0.2 grain slot like he can anyhow. 148 bullets with a Low of 213.1 and a High of 215.1 with a 214.4 average. 124 of those were within ±0.4 grains of the average.

Now the variables that come to mind.

1. That little PACT BBK I have is only accurate to 0.2 grains per the MFG.
2. About a 0.5 grain difference between the 2 cavities.
3. Just how well is that alloy really mixed??? That's about 4.5 lbs of bullets. Is the alloy in the first bullets poured REALLY the same mix as the last one's poured?

I suspect if one knew something about statistics (I don't) the results might be interesting.

Anyone have any thoughts on this?

[TXGunNut]

Sounds good enough to me, I don't weigh pistol boolits at all but I do weigh rifle boolits on occasion. Other than culling obvious lightweights for void or fill issues it doesn't really make much difference IMHO.

[Litl Red 3991]

The alloy not being mixed enough ain't it by a mile. Are you only checking weights of a couple of first out versus last dropped?

Drop the two holes into two different piles. Load 20 cartridges from one pile and 20 from the other. Don't bother weighing them, just go shoot two separate targets with them. See any real difference? It's a far more reliable way to get a good answer to your dilemma than any way known to man.

[Litl Red 3991]

The two holer moulds sometimes drop better bullets from one hole or the other based on your always filling one first. Or because one hole is fatter... or the halves aren't closing square... or...... enough different reasons that over the years, some casters have devised a test. Shoot some bullets from one hole into one target and bullets from the other into a 2nd target and decide.

I've often puzzled over the decision until it dawned on me. Either do it again to get a "second opinion" or realize when it's too close to call, tie goes to the shooter. He's got a good 2-holer.

[Mk42gunner]

I wouldn't worry about the ½grain difference between cavities on the one mold. I would segregate the boolits from each mold, since there is a ~10 grain difference between the two molds.

Robert

[45-70 Chevroner]

I don't weigh pistol boolits, except for reference. After casting a batch I weigh a few just to make sure that I know what I am working with, then mark it on the container. Unless you are shooting compition at long range, beyond a 100 yards, even two grains won't make a lot of difference.

[Mike W1]

Guess I didn't get my point across at all. Sure as heck am not going to segregate bullets by cavity for plinking. I do so by mould due to their differences. My point if I can make it somehow, is it even realistic to attempt coming up with an accurate average of one mould, when the scale is only accurate to 0.2 grs, the cavities differ by 0.5 grains, and the alloy may or may not be consistent throughout the process of pouring. Think it's not likely that I can maybe ever do better than say, in this case, 83% of the bullets were within ± 0.4 grains of the average weight of this batch.

[leadman]

If you are doing a good flux job the alloy should be well mixed. I would not mixed the boolits from both molds together. Only shooting will tell you if it will meet your standards with boolits from both cavities in one mold shot together.

[bhn22]

Alloy temp variance causes weight variations too, as do small differences in technique. Are you bottom pouring?

[Mike W1]

Alloy temp variance causes weight variations too, as do small differences in technique. Are you bottom pouring?

Bottom pouring, PID controlled pot.

[Litl Red 3991]

Weighing makes sense if you want to know quickly if the two holes are throwing different weight boolits. If they are, you know it for sure and can do whatever you think appropriate.

I just finished a batch of RCBS 300gr 40 calibers from a 2 holer. While casting, when convenient two piles were made, one for fronts, one for backs. When they were cool, some of each pile were weighed. It was clear that both holes were dropping the same weight. It took about a minute to check while "quality assuring" the output. All three piles were roughly +- one grain and showed the same weight range. The output from casting sessions get enough weighed to see what weight the lot is, in case they shoot better or not. And some are tested for BHN for the same reason.

When my first digital scale made it possible, that was the first mold that got some serious testing to see what weight variation mattered to a very accurate rifle. Turns out the mold hasn't needed QA verification every time it's gotten it. But thanks to digital scales, it can be done easily whenever.... whenever any question comes up... or just for thehellofit.

[45-70 Chevroner]

I think we really need to get realistic here. First off the fact that your scale is only accurate to with in .02 gr. Is not a factor, by that I mean .02 gr., is minisqual. Your mold cavities being .5 gr difference will only be .52 gr. together. .Under the conditions you have described, a .4 gr difference IMHO is not very feasible. If your boolits are with in 2.0 gr or even a little more you will never be able to tell the difference. Your boarding on OCD and that's really not a bad thing as I myself am.

[BenW]

Different cherries for the different molds, even if the same design. Your alloy change change during casting, but thats only if you let the tin and antimony oxidise out of your alloy.

[MBTcustom]

The object of weighing the bullets as I demonstrated in the "consistency applied" thread, was not very concerned with the mold or the bullets at all. It's more about YOU.

You're using a Lyman mold which is not manufactured to very close tolerances or precision in comparison with the custom molds by Accurate or NOE, so you will likely have weight/size/length differences between the two cavities.
What I would do in your situation is to first witness one cavity with the corner of a file on the meplat so that bullets from that cavity have a tiny tit that distinguishes them from the other.
I would then cast 100-200 bullets and plot a bell curve for both cavities. (Time your pour cycle, and do it the same every time).
If your bell curves have a spread of .7 grains or less, the bullets all appear neither shiny not frosted, the bases and lube grooves are square and well filled, and there is no bumps nor plucking of the sprue hole, I would write down what you did, and never look at it again unless you change alloy.
If there are obvious problems with the appearnace of your bullets or the bell curves are larger than .7 grains (within a single cavity) then make one logical change and repeat the exercise till you are happy with the results.

That said, low speed pistol bullets can be judged nearly as effectively by appearance only. Step up to high velocity rifle bullets and it's a completely different ball game.
I'd say with the bullet mold you are using, control your temperature (good call on the PID), control your timing so they look pretty, and you are 99% of the way there.

[Mike W1]

Sometimes one shouldn't trust memory. Was looking at my manual for that Pact BBK and it says ± .1 accuracy up to about 308 grains and ± .2 from there up to 750 grains. I think I'm happy enough with the results I get from casting plinking bullets which I can do 350-400/hour with my setup and all DC moulds. Back when I did some .30's a with SC and linotype it was pretty easy to keep em' within 0.1 grains so figured my method wasn't all bad. Wife thinks I get some hare-brained schemes on occasion and she's probably right. Aren't wives always??