Weighing casted bullets

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opencountry
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Weighing casted bullets

Post by opencountry » Mon Feb 28, 2022 6:42 pm

I cast/shoot 535-gr. pp money bullets in my two 45-110’s and one 45-90 Shiloh’s. How much variance (weight-wise) is acceptable in target bullets! I’ve been casting, swaging and shooting for years without weighing. Last week I had one round that hit 18” high at 100 yards, and thought it best to find out what others do. Any help would be appreciated. I’m guessing I had a trapped air pocket in one of the bullets.
Robert
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bobw
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Re: Weighing casted bullets

Post by bobw » Tue Mar 01, 2022 1:06 pm

Robert, 535/100=5.35=1% so 535-5.35=529.65 low end. 535+5.35=540.35 high end that's 535+- 1%. Now I don't know one guy on this forum or montana gong shooters who would ever settle for that. .2% would be 1.1 grs or 533.9 to 536.1 there might be some guys who settle for that. .1% would be 534.5 to 535.5grains seems damn realistic to me. With so many factors that will effect your group size hard to say that being inside .1% varation isn't good enough. Practice and wind judging being more important in the general scheme of things. Get a PID controller for your lead pot, work on being consistant in your casting technique. If you can't get by without weighing every bullet, it's your time. Good luck. bobw
bobw

rgchristensen
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Re: Weighing casted bullets

Post by rgchristensen » Tue Mar 01, 2022 2:57 pm

I used to weigh a lot of bullets and worried about it. A test described below convinced me that I was wasting my time. That said, I think it is a good way to learn if your casting process is up to snuff. If you think about it, a bullet which weighs less than the heaviest bullet (bearing in mind that there can be SLIGHT variations caused by how tight you hold the mould, variations in casting temp, etc.) -- if a bullet is "light", it is missing some lead somewhere. Most of the time, this missing lead is caused not by an air bubble, but by shrinkage from the sprue cutter not being the hottest part of the mould. If it solidified first, then there will be a shrinkage vacuole left in the center of the bullet. These vacuoles can be observed by holding a bullet just below center, horizontally in a vise, and shaving them down to center with a sharp wood chisel. They will be found to be about 1mm diameter and up to 5-6mm long.

Now to the experiment: I took a batch of bullets that weighed less than "perfect"** bullets, and wrote the deficit of weight on the ogive of the bullets. They were then loaded, along with 10 "perfect" bullets. They were lubed and loaded and fired (bench/scope) at a grid of aiming points, 60 to 70 of them, if memory serves. The mean point of impact (which was very close to that of the "perfect" bullets) was calculated, and the deviation from the mean point of impact was tabulated for each bullet, along with its weight deficit.

A graph was plotted of the deviation of each bullet from the mean point of impact VS the weight deficit of that bullet. The weight deficits of the 420 gr .40 cal bullets ran up to (if memory serves) over 5 grains. To my surprise, most of the "light" bullets exhibited the same deviation from mean point of impact as the "perfect" bullets. As the weight deficit became larger, there were a few bullets which exhibited noticeably larger radial deviations, but even those bullets that were ~ 5 gr light were mostly "in the group".

As a result of this information, I no longer weigh bullets, except as a quality check on my casting of when using a new mould or a different alloy.

CHRIS

gunlaker
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Re: Weighing casted bullets

Post by gunlaker » Tue Mar 01, 2022 3:14 pm

I've always gone for +/- 0.3gr on my bullets. I have no reason for choosing that number other than it makes me feel good, and it's pretty easy to keep the vast majority of a 100 bullet batch to within that tolerance anyway.

Chris.

opencountry
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Re: Weighing casted bullets

Post by opencountry » Tue Mar 01, 2022 8:43 pm

Thank you very much bobw, CHRIS and Chris. I’m
humbled that you offered so much in response. I understand the importance of consistency in casting methods. I started casting bullets back in the late 70’s when I bought my first Sharps from John Shoffenstal (sp) of C.Sharps when he first began offering his rifles here in Richland, WA.
At any rate I try to be as consistent as I possibly can while casting, and I cast a lot at one ‘setting’. I appreciate everyone’s input, and I did learn from reading your offerings. I make a habit of waiting at least (72) hours before swaging the lubed bullets .001” through a Lee sizer in an RCBS Junior press. I think it’s of utmost importance to really ‘square-up’, or ‘center’ the unsized bullet on the top of the ram in the press before sending it through the sizing die. This may have been the problem or weak link which caused the flyer…maybe. While I was hurrying-up the process I may have pushed a bullet up through the sizing die without it being truly centered. I’m really going to take my time doing this in the future!
Thank you all again. It’s much appreciated!
Robert
Beware of the man that owns one rifle.

1minute
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Re: Weighing casted bullets

Post by 1minute » Wed Mar 02, 2022 7:01 pm

Interesting and timely as I just went through this exercise with a new Brooks mold for slugs to be launched from a Long Range Express in 45-90. Did a quick run of 55 with weights ranging from 535 to 542.5 grains with nothing being tossed. Mean was 540.85 and sdev was 0.0707.

I did have some issues getting proper sprue plate tension during the pour and suspect that contributed to my variation. To my untrained eye, that looks to be where inconsistencies are most prominent.

Picked out the 25 slugs closest to the mean. They range from 540.2 to 541.3 (spread of 1.1 grains) with an average of 540.75 and sdev 0.778. Will load those in order from lightest to heaviest and see how they do.

Expectations are that I'm so unstable the mechanics won't show a discernable effect.

Have a good one,
1Minute

MikeT
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Re: Weighing casted bullets

Post by MikeT » Wed Mar 02, 2022 10:04 pm

1minute, Once you get the casting temperature to stabilize [that is the mold & the melt], expect your bullets to fall within a range of three grains without much problem. Then you can weight them so you can sleep well at night or just shoot them in weight order.

Keep on hav'n fun!
MikeT

opencountry
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Re: Weighing casted bullets

Post by opencountry » Wed Mar 02, 2022 10:13 pm

MikeT wrote:
Wed Mar 02, 2022 10:04 pm
1minute, Once you get the casting temperature to stabilize [that is the mold & the melt], expect your bullets to fall within a range of three grains without much problem. Then you can weight them so you can sleep well at night or just shoot them in weight order.

Keep on hav'n fun!
MikeT
Three grains. I'll weigh and test these on paper the first good calm morning we have.
Thanks, Mike.
Robert
Beware of the man that owns one rifle.

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bpcr shooter
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Re: Weighing casted bullets

Post by bpcr shooter » Mon Mar 07, 2022 8:28 pm

We use +/- 2gr at the most. If you have LOTS of time on your hands, I sure having them all the same wouldn't hurt, but I would worry about making a good wind/mirage call more.


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opencountry
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Re: Weighing casted bullets

Post by opencountry » Mon Mar 07, 2022 9:41 pm

bpcr shooter wrote:
Mon Mar 07, 2022 8:28 pm

…but I would worry about making a good wind/mirage call more.


matt
I agree, Matt. I agree.
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bobw
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Re: Weighing casted bullets

Post by bobw » Thu Mar 10, 2022 9:20 am

opencountry wrote:
Wed Mar 02, 2022 10:13 pm
MikeT wrote:
Wed Mar 02, 2022 10:04 pm
1minute, Once you get the casting temperature to stabilize [that is the mold & the melt], expect your bullets to fall within a range of three grains without much problem. Then you can weight them so you can sleep well at night or just shoot them in weight order.

Keep on hav'n fun!
MikeT
Three grains. I'll weigh and test these on paper the first good calm morning we have.
Thanks, Mike.
Robert
When I'm at temp on the melt and mold I figure I'm fugging up if I have anymore than + or -.7 grains.
bobw

JonnyV
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Re: Weighing casted bullets

Post by JonnyV » Fri Mar 11, 2022 7:17 am

I got a set of the nice casting handles that Shiloh sells, the Canadian ones with the locking feature. The first thing I noticed using them is that my hands don't get near as fatigued as with the Lee/Saeco/RCBS type handles. After 33 years of construction, many of my joints are in really bad shape, and my hands are especially bad off. Next thing I noticed is that once the pot had stabilized at 800 and the mold was up to temp and casting good bullets, they started dropping super consistent, like as in about a 1.5 gr total spread top to bottom. This means I can sort my bullets into lots that all fall within a half grain range without much problem or having very many culls. Certified alloy from John Walters is a big help too.

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kenny sd
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Re: Weighing casted bullets

Post by kenny sd » Sat Mar 12, 2022 7:33 am

I only shoot at 100, so I weigh for 'fun'.
my 40 70 SS and the BA 390 GG round nose is close to the original load.
mine is 63 to 65 1 or 1 and 1/2 fg.
I cast in 1 20...
I weigh all from 392 too 395, with most being .395.
I check each base for bubble holes. and discard any that even LOOK bad.

I weigh because once in a while I'll get a .387.....that to me means a bubble in the cast.

so, If I didn't weigh, I would miss that bad bullet and wonder about the 'flyer'. A bubble in the bullet is never dead center and
you can count on a 'wobbler'.....
just my thoughts, and I shoot only for fun and against only myself. Ken

MSalyards
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Re: Weighing casted bullets

Post by MSalyards » Sat Mar 12, 2022 11:26 pm

When I first started shooting and loading black my targets looked horrible. I only was shooting 100 yds and was buying cast bullets from everywhere. I wanted to start casting and called Paul Jones for a mould. My store bought bullets were often off as much as 10 gr apart. After explaining my problem Paul told me that at 100 yds even those crappy bullets should shoot1 hole. Ha! That was many years ago and I did purchase a mould from him. Still not shooting 1 hole that often, sometimes I'll piggyback 1 or 2.

Kurt
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Re: Weighing casted bullets

Post by Kurt » Mon Mar 14, 2022 5:06 pm

I have split light bullets in 1/4's and never seen a bubble but I have seen dross from the spigot of the ladle get into the cavity.
I pressure cast and let the pour vibrate the alloy over the hole and from heavy to light I seldom see more than 5/10 from light to the heavy end. Just a couple nights ago after reading here I for the heck of it weight 50 before I patched them and the spread was 5/10 gr with 50 cast and most were with in 3/10 quite a few the same weight.
Try this some time when you cast. Hold the mould on it's side and start the pour then slowly turn the mould upright and let the ladle spigot rest on the hole for about 2 seconds then raise the ladle letting it empty over the hole, yes I'm a messy caster :D, what this does is create a vibration that settles the alloy.
Cast a couple exactly like this and make sure the ladle is the same hight above the plate each time.
Let a couple bullets cool and mark them so they don't get mixed.
Now cast a couple with pouring the alloy in and just roll the ladle off the hole and stop the pour. Weigh them. You will see a lot lesser weight bullet even if it looks perfect. Changing the hight I mentioned more of less will change the weight.
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