Significance of variance in bullet weight?

[jabilli]

For some reason the search function isn't working for me? I'll just hope it's not a dupe.

For some reason or another I felt compelled to measure the weight of each bullet in a batch I made recently. I wasn't terribly satisfied with the results. I'll do number crunching to find standard deviations and such later, but I found that the bullets (Slightly more than 150 of them) varied. The spread is from 126.8 grains to 132.5 grains. Does this have a significant effect on the accuracy of the batch?

I've found in other forums people claiming that it's not really a big deal, I wanted to confirm it through you guys.

I started wondering why there was so much variance in the weight of the bullets...Then it dawned on me that the lead ingots that I made from wheel weights are not all uniform in alloy composition. If I were to make a big batch with all of the ingots, then the weight in each ingot would be uniform, but since I made the ingots as I went along gathering wheel weights, I'd expect different compositions.

On that note- I was trying to think of other possible causes of variance in bullet weight and wondered if the temperature of the smelted lead might have an effect on bullet weight (I realize this could be a silly question but this stems from the premise that heat affects pressure, possibly changing the density of the lead)...

Also, does the lead temp affect size? ....are there a few thousandths of an inch differences between different lead temps?

[Old Caster]

That is quite a varience and yes different alloy makes quite a difference in weight. Also if the temperature is higher the bullets will be heavier until they get hot enough to severly frost where even the side of the bullet can be curved in. It will be obvious when they are sized. There is also a difference in weight if they are ladle cast, bottom poured or pressure poured with a bottom pour pot. How much varience matters, depends on what you are shooting (rifle pistol) and whether you are just plinking or competing. For most shooting, if it looks good shoot it. When everything is right the only time a bullet is made that isn't up to par is when cadence gets upset. -- Bill --

[jabilli]

I think soon I'll start up a mini-experiment, make a batch of bullets all the same weight, and a batch of bullets where the ingots provide variance of weight because the ingots aren't all exactly the same composition. I've a bench rest but Id really like to use a clamp of some sort to take out the human element. I'll post up the results

[paul h]

So far I've never weight sorted cast bullets. I've found with a good visual inspection to cull those with voids and incomplete fillout I get handgun and rifle bullets that will group 2moa after I find a load the gun likes. This is with 35 caliber and larger bullets.

I knew if I ever individually weighed bullets it would be sickness that would take a hole bunch of time that I simply don't have.

If I was engaged in competitive shooting, I'd absolutely weigh each and ever bullet and sort them into batches. But I don't compete so don't see the benefit of the additional work. I'll be blissfully ignorant of the weight variances of my bullets so long as they group well enough for me.

[runfiverun]

alloy/mold temp,and alloy variations will cause the weight to up and down.
if i am doing boolits for an accurate rifle i'll run the pot down pretty far,and return the hot sprues to the pot concentrating on a cadence.
30 lbs of 165 gr boolits is a single lot.
for my revolver cartridges, and 2-3" guns, i'll keep the ingots warm and the pot full but still rely on a consistent cadence and a consistent alloy to keep things close.

[MtGun44]

Of course it's a dupe. There are very few questions that have not been asked previously
and discussed.

That doesn't mean that it is a bad question or should not be answered. IME, there is a
small bit of effect for pistol loads, but I have not really been too worried for ordinary pistol
shooting.

If I was shooting matches where trophies were at stake, I'd want tighter in a RIFLE,
and maybe even in a pistol if the shooting was a 50 yds or more. If it were pistol
silhouette, I'd hope for pretty tight weight matching.

For most purposes, not too critical if the boolits look good.

Your proposed experiment is exactly what needs to be done for you to learn about
your issue. That is a lot of what this hobby is about.

Bill

[pdawg_shooter]

I weigh all my RIFLE bullets, and allow + or - 1% of average. Works for me anyway. For handguns, if they look good I shoot them.

[bruce381]

when i get going good mine run <1/2% variation good for me on steel shooting. I run hot and kinda frosty

[.22-10-45]

Hello, jabilli. When I first started casting .22 bullets nearly 20 years ago, almost 1/2 were rejects..huge weight difference & casting flaws. Now I may only have 5 or 6 bad ones out of a hundred..there is a learning curve. There is one item that did make a big difference..a clock with a large easy to see second sweep hand.
After pour, I watch sprue to harden..then I watch clock. depending what I'm casting, anywhere from 3 to 6 seconds lets me cut sprue without tearing..and even more important..keeps a steady rythem for consistant mould temp.
If casting heavy .40 to .45 rifle bullets, or if mould becomes too hot, a large block of copper or aluminum makes a good heat-sink to cool sprue plate.

[missionary5155]

Good morning
Back when I was shooting Revolver Silly Wets my match boolits in 41 mag were all within 1 grain. 220 grain was the base line. For practice I expanded that to 2 grains sorting into groups of above weight, below and at that base weight. Just me. I wanted every edge I could get. Won ILLinois AAA Revolver in 1984 with my Dan wesson 41 mag 8 inch. I still weigh my boolits that I want the best accuracy loads. If it is just to pop bowling pins at 100 yards then visual inspection as it is handled is good enough. But to hit an egg at 100 yards with a Krag I need all the help I can get.
Now for just plain fun.. I casually look at each boolit during casting, sorting, lubing and loading. If I see a defect it gets tossed into the coffee can for remelt.
Mike in Peru

[fredj338]

As noted, alloy & temps are causing the variation. I only weigh hunting bullets & my rifle bullets for most consistancy, a 1% variation from average is max. For handgun practice bullets, I never weigh after the first casting to get a close bullet wt for reloading data purposes. Huge swings from average can indicate internal voids or improperly filled bullets. At 5%, seems like you may have fill out issues.
As an aside, I accuracy tested some "bad" bullets the other day in my IDPA gun, an XD45TAC. The bullets still grouped under 2" @ 15yds. All had some base deformity that had me culling them during sizing. If that won't throw flyers, then slight wt diff won't either out to 25yds.