Weight variation

[Planeguy]

Greetings, I just got started casting and would like suggestions on what constitutes an acceptable variation in boolit weight. I have been casting some boolits for a .416 Ruger. Most come out within a .5 grain range. Mold is a brass NOE .418 350 gr RNFP. Boolits are dropping out at 345.5 +/- .5 grain with a few outliers that go straight back into the pot. What factors can contribute to more consistent boolit weights? Thanks,
Planeguy

[Winger Ed.]

That variation is pretty normal.
As long as they look good,, I'd keep 'em.

If the variance is one full grain from heaviest to lightest--
Without pulling out the calculator: I think that is less than 1/3 of 1% for the weight of boolits you're working with.

In a perfect world, they would string up/down with the weight difference,
but I'm sure as the world not a good enough shot to be able to tell the difference with yours if/when they did that.

If you want to challenge yourself and eliminate a possible variable-
set a few aside that are exactly the same weight, and shoot a group or two with them.

Then shoot a couple groups with 2-3 each of the extreme difference.

I don't think you'll see much if any difference, but then you'd know for sure.

[hawkenhunter50]

I agree with Winger, 0.5 grain variance you're doing good.

[justindad]

Single cavity mold and consistency of sprue cut is where I would need to look if I wanted less than a 1.0 grain variance. I tend to tear a bit of a divot when I cut my sprue.

[megasupermagnum]

.5 grain variation on a bullet that size is quite good. You will improve even more as your casting improves. If you are sorting them to get rid of any with defects you can see with your eyes, .5 grain variation will shoot fine. If you wanted the best of the best, there is nothing wrong with weight sorting to an even tighter level.

Really what causes weight variation is going to be inconsistency in your casting. The mold being hotter or colder, any voids in the bullet, inconsistency in your sprue cut, etc. It is very difficult to get a picture perfect sprue cut every time when casting with an alloy that has antimony in it. It can be done, but it's normal for my good bullets to have a sprue cut with imperfections. It's at the center of the bullet where it should have minimal effect. You are better off running hotter and getting perfect fill out with less than perfect sprue cuts, than running cold with poor fill out, and getting perfectly smooth sprue cuts. If you are getting large divots, then you are too hot. On a bullet that size fill rate starts to become an issue. If you are currently using a bottom pour, you may find it easier to get good bullets with a ladle. Another factor could be the pot temperature. If you are running a basic melting pot such as a Lee 4-20, the thermostat in them is only so good. They work fine for most things, but it's not uncommon to see 30F degree swings. By using a PID controller you can keep your pot temp to within just a few degrees. After that it's all about cadence and sprue puddle size. Cadence to keep your mold at the right temp, and sprue puddle to keep your sprue plate the right temp.

It's not easy, .5 grain variation on a 350 grain bullet is pretty good for a start. That's better than I did for quite some time.

[BLAHUT]

Depends on what you are trying to achieve ? Just good bullets, bullets that weigh all the same, accuracy at distance, are you weighing each powder charge, each peach of brass, each primer, each loaded cartridge, looking for extreme accuracy out at yardage, or just hit a 6" pie plate at 100 yds.
I weigh each and every bullet and sort by .o1 grains. Every cartridge in my 50 round box weighs exactly the same, then I know if its not grouping at 400 yds its me...

[lightman]

I'm going to say that is pretty good. I see .3 of a grain pretty often with my lighter pistol bullets. Some of this can be skill but it also depends on the mold. All molds don't drop the same weight or diameter of bullet from each cavity.

[Dusty Bannister]

Then after all that inspecting, you may use a volume powder measure and have some variation, or weigh every charge of powder for the cartridge. Cases all from the same lot, primers all from the same make and lot? That sure takes the fun out of shooting for some of us. Sooner or later, you may decide all that extra work is not worth the effort.

[racepres]

Depends on what you are trying to achieve ? Just good bullets, bullets that weigh all the same, accuracy at distance, are you weighing each powder charge, each peach of brass, each primer, each loaded cartridge, looking for extreme accuracy out at yardage, or just hit a 6" pie plate at 100 yds.
I weigh each and every bullet and sort by .o1 grains. Every cartridge in my 50 round box weighs exactly the same, then I know if its not grouping at 400 yds its me...

Then after all that inspecting, you may use a volume powder measure and have some variation, or weigh every charge of powder for the cartridge. Cases all from the same lot, primers all from the same make and lot? That sure takes the fun out of shooting for some of us. Sooner or later, you may decide all that extra work is not worth the effort.

If I could Shoot well enough to make all that worthwhile...welp I may (or may Not) do it.. Certainly Not now that I am pushing the 70 YO mark!!!
Wanna see how steady you are??? Put at least a 4 power scope on yer handgun... set it on Bags even...
Nah... Couple inches at 50!!! Minute of Pie Plate to 200 yards is Great... With my eyesight, I wouldn't be able to Identify the Target species from farther!!!
Sure don't wanna accidentally shoot a Dog... even if it shouldn't be in that field!!
Last time I asked the local critters to sit still whilst I fetch binocs/spotting scope, they ignored me!!!!

[Planeguy]

I have an RCBS bottom pour pot. My main interest is in hunting. I figured the big boomer would work great with cast boolits for hogs. I can get boolits without wrinkles and obvious voids but even with the brass NOE mold I get inconsistencies that must be due to temp control. Shiny noses with frosty boolit shank, all frosted, etc. Didnt think that would throw weights off but apparently it does. I sorted out enough to try loading them up. Waiting for a lube order to arrive.

[Bigslug]

Half a grain extreme spread on a bullet that large isn't anything I'd be worried about. Certainly not for the cartridge and application.

Starting with the mold on a hot plate helps, as does a PID controller for regulating pot temperature and providing you with a digital readout. I typically run my pot somewhere in the 750-800F range for somewhat-harder-than-wheelweight mixes and brass molds, and I go straight to a refill as soon as the mold is empty unless I'm getting signs that temps have increased too much (rare).

Keep in mind also that there may be tiny variations between your cavities, or in sprue cuts, and there's not much to be done for it other than deciding how much variation you're OK with. If the bullet isn't for match purposes, looks good, and you're consistently throwing under 1% weight variation, I'd load them and move on with the task at hand. The pigs will still be 100% dead.

[rintinglen]

Megasupermagnum pretty much covered the spectrum of user-caused variance. But there is also equipment caused variation. Back in the day it was not uncommon for different cavities in a multi cavity mold to vary by a grain or even two. Users were advised to put a small punch mark in one cavity on a two cavity mold and then use that to sort the boolits. In fact, I have a two cavity 311-041 that is so marked. But what I found was that the lighter boolits from the one cavity overlapped the heavier boolits from the other, and that from my 30-30, either would shoot to "minute of Ram" whether I weight sorted or not. In fact, I eventually quit sorting all together and bought a 4 cavity Lyman. I have no idea if the cavities cast different or not. For most uses, weighing is not required. Simply carefully inspect each boolit, looking for perfect bases and complete fill-out. The ones that look perfect will vary little. But even ones that aren't perfect can still shoot pretty darned well. Unless you are a fan of Bench rest, long range, shooting, "good enough" will be just fine.

But as you have seen, casting technique, alloy used, mold temperature and the level in the pot all can affect bullet weight. Close attention to these conditions will minimize variance. For a heavy boolit such as you are using, a half grain, plus or minus, is virtually negligible.

[quilbilly]

Over the years, I have not found that anything less than .75% variance around average for a mold between boolits to make an appreciable difference in accuracy at 100 yards.

[BLAHUT]

If I could Shoot well enough to make all that worthwhile...welp I may (or may Not) do it.. Certainly Not now that I am pushing the 70 YO mark!!!
Wanna see how steady you are??? Put at least a 4 power scope on yer handgun... set it on Bags even...
Nah... Couple inches at 50!!! Minute of Pie Plate to 200 yards is Great... With my eyesight, I wouldn't be able to Identify the Target species from farther!!!
Sure don't wanna accidentally shoot a Dog... even if it shouldn't be in that field!!
Last time I asked the local critters to sit still whilst I fetch binocs/spotting scope, they ignored me!!!!

Then just shoot them bullets and smile...

[JSnover]

If the bullet isn't for match purposes, looks good, and you're consistently throwing under 1% weight variation, I'd load them and move on with the task at hand. The pigs will still be 100% dead.

^That!
Work out your variation as a percentage of the intended weight, you'll slip a lot easier.

[racepres]

Then just shoot them bullets and smile...

Been Working for Me...Thanks

[charlie b]

I don't weigh pistol bullets, at all. Just cast and go.

Rifle bullets for plinking are +/- 0.5gn. Rifle bullets for precision are sorted in 0.1gn batches. Best bullets for long range shooting are at the top 1/3rd of the weight range.

[farmbif]

let me explain a little experiment I did a couple years ago. first off I'm not a benchrest, high-power or any other type of competitive shooter. if I can get my loads to do 1 1/2"-2" or so at 100 yards in a rifle I'm real happy. I got a new mp454640 mold to load 45 colt for a lever action Rossi . it came with 4 hollow point pin options, flat for solid bullet, small round, large round and the mp penta hollow point. I put a different pin in each of the 4 cavities of the mold. I worked up a load to 20 grains of 4227 and was real happy with the power, accuracy and velocity over my old chrono was right about 1200fps with all the bullets weighing from 255 grains to 275 grains and the accuracy also was very close to all being the same. these were very unscientific tests all shots were from standing position and I was shooting at 2x4's, trees and other pieces of wood stuck in. the ground at about 65 to 70 yards. what I cant explain and was a truly amazed at is that the velocity was within about 50 fps difference between the different weight bullets

[dverna]

There is a point of diminishing returns when chasing accuracy.

What others have alluded to is important. Just how accurate does it need to be?

Take 5 bullets that weigh 345 gr and 5 that weigh 346 gr and fire a 10 shot group.

Take 10 bullets that weigh 346 gr and repeat the test.

If you have the time and resources, do the test a couple of times.

I doubt you will be able to tell the difference. But if there is a difference, is it meaningful for your intended purpose?

[charlie b]

Ditto. The difference was worth the effort for me. What was the difference? Almost 2MOA vs ~1MOA depending on how closely the bullets are sorted.

BUT, along with that is sorting cases, match primers, carefully weighed powder charges, checking runout, etc. As is finding the correct powder charge and seat depth for your rifle. And then there is you and your shooting technique. Then you'll want a custom barrel for your cast shooting.

Once you go down the rabbit hole you'll find there is no bottom