Cast bullet weight consistency

[Hook]

When casting bullets for high performance rifle loads, what weight consistency do you shoot for? For instance, I'm casting 30 cal bullets using the 170 gr Lee FP and 180 grain RCBS FP right now. When y'all do such casting, what weight consistency (+/_ X.X grains) do you strive for? Or maybe it should be expressed in terms of percentage because of the wide range of bullet weights we cast....

[JonB_in_Glencoe]

I've seen 3% deviation in factory jacketed bullets
When I spend time to weigh sort cast rifle boolits, I shoot for 1/2%

[Winger Ed.]

Short range handgun boolits- if they look good, I shoot 'em.

For .30cal, I can live with 2% variation without any problem.
I do that for a large batch of target/practice ammo.

I'll often do a lot of 100, and tweak them out to the last little variable I can to see how good I am without room for excuses.

[HWooldridge]

I normally will pass 2% - BUT - more likely that I’ll weigh each bullet and put them into batches. I’ll usually get three groups- high, middle and low, then I’ll mark three containers accordingly and keep them separated until it’s time to load.

[BLAHUT]

For myself, when I cast, I spend time and cast a bunch, then I will weigh everyone and separate them into piles that all weigh the same. When I load,
I weigh everything, every carterage in the box weights the same, I load for extreme accuracy. That way, if there is a difference on target, I know it is me, not the ammo.
I load all my ammo as if it were for matches. All my ammo is either for practice or matches, it's all the same, I do not segregate one for the other. This difference shows up when you get out to the longer distances, I do all my practice at 400 yds, that as far out as I can get at the range I belong to, If longer was available to me, I would practice at the longer range.
I find; I have a thousand questions, for every one answer I have.
For the few grains of weight difference, box to box, everything in each box of 50 of mine is exactly the same weight, if they are all the same, that's why there are those twisty turnery things are on the back of the rifle's, for the different weights ???
I am never just close enough ??

[charlie b]

When I started casting for my .308 I was happy if my bullets were within 2 or 3 grains of each other (180 and then 210gn bullets). They did fairly well, 2MOA or so out to 300yd.

After a few years I refined my technique and most of my bullets are in a 1gn spread (less than 1%). I then sort those into batches of 0.1gn. The "heavy half" I reserve for when I want really precise loads at higher velocities. I strive for consistent MOA groups, but, am not there yet. I am close though :)

When I get a new mold I will experiment with it, mostly finding the casting sequence that keeps the mold at it's 'happy' spot. Each mold is a bit different and takes me a couple hundred rounds to figure it out.

[Hook]

Thanks for the responses gentlemen. It seems that I am pretty much in line with most of you. I began casting again about 2 years ago when I got interested in PC'ing. I'd played with casting in the 80s but lost interest. I cast a large number of 170 gr Lee FPs and 180 Grain RCBS FPs 2 years ago and got good success accuracy wise and velocity wise (because of the PCing). Unfortunately, I was having to play with different alloys and couldn't really get a handle on where I wanted to be WRT velocity, accuracy, and expansion. I also removed the lube from a large collection of commercial and otherwise 'acquired' bullets, powder coated them, and shot them.

I recently realized that the stash was getting low. I'd shot a lot of them and given a large number away to interested friends. Since I'd managed to settle on a favorite alloy and have a good supply in hand, I decided to standardize on that alloy and two bullets. Since I do want to use them for deer, I figure my 10.6 BHN alloy (according to the spreadsheet) cast in either of the aforementioned FP molds, would work well.

I just finished casting several hundred of each and began weight sorting them yesterday, starting with the RCBS. I'm not through yet, but so far they have fallen almost completely into two batches within one grain, 182,X and 183,X. Out of the 4-500 sorted so far, there have been 4 bullets over 184 and about a dozen under 182 (not counting a few visually culled). This seems pretty dang consistent to me. At this point, I could combine the two groups and have a batch that is +/- one % or keep them separate and have 2 batches of +/- 1/2 %.

It was at this point that I decided to post my question to see where others draw the line with acceptable and unacceptable. Thanks for you inputs.

[racepres]

I normally will pass 2% - BUT - more likely that I’ll weigh each bullet and put them into batches. I’ll usually get three groups- high, middle and low, then I’ll mark three containers accordingly and keep them separated until it’s time to load.
My Method also.. I certainly would Not worry over 1/2 of one Percent!!!

[georgerkahn]

When casting bullets for high performance rifle loads, what weight consistency do you shoot for? For instance, I'm casting 30 cal bullets using the 170 gr Lee FP and 180 grain RCBS FP right now. When y'all do such casting, what weight consistency (+/_ X.X grains) do you strive for? Or maybe it should be expressed in terms of percentage because of the wide range of bullet weights we cast....

For "high performance load" I sort all pleasing to my eye bullets by weight, using a + or - 3 grain criteria. Those in the 3 - 5 grain pile generally get loaded and are shot, too -- but not for my "hopefully the best" targets. Most any/all out of this range are returned to the pot. Friends have suggested I load these and use them for "barrel fouling" 1st shots -- but, to me, this is just an added complication to what is hoped for a great day at range. I will add that in my "real" search for one-hole in target with my XP100 in Fireball, I have reduced criteria to + or - but one grain...
geo

[Larry Gibson]

When casting bullets for high performance rifle loads, what weight consistency do you shoot for? For instance, I'm casting 30 cal bullets using the 170 gr Lee FP and 180 grain RCBS FP right now. When y'all do such casting, what weight consistency (+/_ X.X grains) do you strive for? Or maybe it should be expressed in terms of percentage because of the wide range of bullet weights we cast....

When casting for my high performance rifle loads [match grade for accuracy at standard velocity up through very high velocity] after a very anal visual inspection I weight sort 30 XCB and 314299 bullets to .3 gr variation of the top weight bullets. That is just about two tenths of one percent variation.

For softer cast high performance hunting bullets I weight sort 188 gr 311041 HPs to a top end weight variation of .5 gr.

Remember that any weight variation in a cast bullet means there is an imbalance somewhere in the bullet. The greater the imbalance the greater the adverse effect of the RPMs centrafugal force will have on that bullet during flight. That translates into a loss of accuracy, sometimes small and sometimes large depending, which is a loss of performance.

Weight Sort 30 XCB Cast Bullets


"For your theory, that lighter bullets in a batch are less accurate than the heavier ones we must assume: 1. that light bullets are caused by voids, 2. that those voids are not too near the longitudinal axis and, 3. that they are large enough to be significant."

Ergo is the problem in this discussion. I do not subscribe to any of those 3 assumptions. In fact if you re-read my post with the graph I explain what I've found to be the real problem and it is not the suspected or assumed "voids" in the bullets. Yes, that's what we've all been told for probably a hundred years and it is what we've based our testing on.

Ten years ago I thought I was casting pretty good bullets, excellent in fact. However. the more I got into shooting cast bullets at HV I found while I was casting good, excellent bullets I too hit the accuracy wall that joeb is alluding to. I also found that when those cast bullets were pushed to really HV (2500 - 3000+ fps) they did not do as well as expected. Back then I was weight sorting as we've all been told to. If you line them out by weight you get the so called "bell curve". In proving insanity I, like you and everyone else, then did the same testing of each .1 gr testing over and over again expecting different results.....we all got the same results; accuracy was not really improved via that method no matter how many times we ran the test. You are asking me now to run the same test and think I will come up with different results? It wouldn't happen.

Let's assume we have a mould that will cast perfectly even bullets in all dimensions. Not an assumption but fact is that mould has a finite capacity for any alloy. Thus if we cast with a good alloy giving the best fillout then only those that weigh the heaviest will have filled the mould out completely. Any bullets with less weight are then not dimensionally the same. We may not be able to measure other than weighing that difference but the difference is there in lighter weight bullets none the less. Now that difference in weight (mass) is there but it is not predictable.....we don't know where in or on the bullet that difference in weight is missing from. The missing weight is what creates the imbalance. I suspect voids in the alloy are not the problem but rather other aspects are which I have previously discussed.
I recently cast 542 NOE 30 XCB bullets of #2 alloy. I have just completed weight sorting them. In the next post I will show the graphed results of the weight sort which should aptly demonstrate what I'm saying. Have to copy, download, etc. so it will be an hour or so.

Here is the results of the weight sort. 542 bullets were cast of Lyman #2 alloy and WQ'd. They were then aged about 12 days before I got around to weight sorting. Here is my set up for weight sorting. I visually inspect each bullet for any defect. If any is found that bullet is rejected to be melted and recast at a later casting session. Those that pass my anal visual inspection then have any remnant of the sprue cut off. That is done on the lead block with a sharp blade on the pocket knife. The bullet is then weighed on the Redding balance beam scale. While waiting for the beam to settle I then visually examine and sprue cut another bullet. With the magnifier in front of the scale I can readily and accurately see what the weighed bullets exact weight is. The bullet is then placed in a bin for that weight.

Of the 542 bullets weighed 22 were rejected for a visual defect or because they weighed less than 156.9 gr which means the weighed ones had passed the visual inspection but still weighed way lite. The remaining 520 XCBs were weight sorted into separate bins of .1 gr increment from 156.9 gr to 158.0 gr......a 1.1 gr spread.

313472

Here is the rough graph of the weight sort. As you can see there is no "bell curve". The curve rises from 156.9 gr slowly to 157.5 gr and then rises sharply. The "curve" then plateaus out at 157.7, 157.8 and 157.9 gr with 113, 124 and 110 bullets for each weight. The "curve" then falls sharply to just 9 bullets at 158.0 gr. Of those 9 bullets only 2 actually weighed 158.0 gr. The remaining 7 bullets weighed between 157.9 and 188.0 gr. There were no bullets heavier than 158.0 gr.

313473

The weight sorting is showing us the 113 bullets of 157.7 gr, the 124 bullets of 157.8 gr and the 119 bullets (I'll put the 158.0 gr bullets in with those) of 159.9 gr weight has the highest weight/mass of alloy in them. Since the curve dropped off suddenly we see those weight bullets are the most consistent and the best the mould will produce with that alloy. Those 356 weight selected bullets will be used for best accuracy.

The 157.6 gr bullets will be used as fouler/sighters as I expect they will give very good accuracy also given only a .2 gr +/- difference in weight.

Had we lumped all the visually selected bullets into one group 70% would have been with the excellent bullets, another 15% would have been with the fouler/sighter bullets and the remaining 15% would have been with bullets having a weight/mass difference of 1.1 gr. Now, had I done that I probably would have got nice 1 1/2 moa groups with 7 +/- shots going into moa or less and 2 -3 +/- shots going out of the group in the 1 1/2 moa +/-. How many of you shoot groups like that with bullets only visually sorted?
It is with such weight sorted selected bullets (the 157.7 to 157.9 gr bullets) that I am able to hold moa accuracy to 300 yards and beyond with a 2900+ fps velocity.

That is how I weight sort and why it makes a difference



Note; Since that was accomplished 6 years ago I have further refined my casting technique to where, out of a casting session producing 500 + bullets, 70+ % will be within the .3 gr variation mentioned. Of course, the larger the bullet the greater the variation can be and still maintain "high performance". My 314299s weight sorted for CBA military rifle match have a variation of .5 gr.

[racepres]

For "high performance load" I sort all pleasing to my eye bullets by weight, using a + or - 3 grain criteria. Those in the 3 - 5 grain pile generally get loaded and are shot, too -- but not for my "hopefully the best" targets. Most any/all out of this range are returned to the pot. Friends have suggested I load these and use them for "barrel fouling" 1st shots -- but, to me, this is just an added complication to what is hoped for a great day at range. I will add that in my "real" search for one-hole in target with my XP100 in Fireball, I have reduced criteria to + or - but one grain...
geo
Great for 200 gr boolits... not Great for a 55 gr boolit!! I weigh the percentages...and since I am Not that good a Shot...and I do Not normally shoot for "group" over 100 yds, less with a Handgun... my Percentages are Liberal!!

[Digital Dan]

All bullets are weighed and then sorted into equal weights and so loaded. Lacking time for such exercises I use a .3% spread for each lot.

[high standard 40]

Larry. The weight sorting system you detailed is the very same method I have arrived at, using very similar logic. It works well for me.

[Bigslug]

If I was going down this road, I would put the work into determining how much of it actually matters, and to what degree. For the record, I don't personally sort bullets by weight. If it's good to the eye, it's usually good to the scale - certainly in the .30 cal spectrum. But if I were gonna:

After a visual culling of the obvious duds, I might sort a batch for weight, cull anything weird on the extreme fringes, and then load them, keeping each weight class separate. Then I'd subject them to whatever chronograph and group testing gives you the warm fuzzies. To make it simpler, I'd probably shoot 20 rounds of the light, 20 of the heavy, and 20 in the middle.

If that batch testing gives you differing results you can quantify, AND THAT ARE RELEVANT TO YOUR SHOOTING, carry on with that process. If not, you now know that you were just spinning your wheels with mental masturbation and can spend your time more productively without robotically weighing every single slug.

[HWooldridge]

FWIW, I once weighed a box of 50 Nosler .338 250 gr JSP bullets, and the total spread was about 2.5 grs. Of course, they are producing many thousands in a batch and packaging cartons from the total run.

My .338 WM Ruger 77 would shoot MOA groups with this pill and I never sorted by weight. I’m sure you would see the difference at some distance but a lot of other variables are also at play.

[porthos]

many years ago i bought a electronic scale to check bullet weight. a waste of money. my bullets weight +- .01 (1 tenth grain) occasionally 2 tenths. i think the reason is that i have a good tenique and i LADLE CAST

[stubshaft]

many years ago i bought a electronic scale to check bullet weight. a waste of money. my bullets weight +- .01 (1 tenth grain) occasionally 2 tenths. i think the reason is that i have a good tenique and i LADLE CAST

AND a good mold! I've seen 3% variation between cavities in RCBS and Lyman molds.

[Harter66]

I whine about 3.5% deviations in a casting session or 6c Lee . I have a 3 cav NOE 460-543 that delivers 1 gr across 10# of ladled bullets which on a 535 ain't much . At the other end of my scale resides 225-62 . I scale cull those for important stuff to .3 because that's about as close as the digital scale on hand will hit consistently . 1 gr is huge on a 62 gr 22 .

I guess that translates to something like .2-.5% .

I'm told that 2% is close enough .

[405grain]

When I'm trying for maximum accuracy, first I visually sort the bullets for any defects. I don't want any rounding of the shoulder on the gas check shank, any blemishes or tiny pits, and no finning what so ever. Then, from the bullets that are visually "perfect", I weight sort them into three groups: light, medium, & heavy. The bullets in the "medium" category must all fall within +/- 0.2 grains of each other. All of the bullets that are too heavy or too light are put together in a bag that's marked "practice". This is really a lot of overkill, but doing this meticulous sorting is part of the load development required for shooting sub MOA cast bullet loads (done only for the bragging rights and sense of personal accomplishment). For general purpose hunting and target shooting, loads with this extreme selection process just aren't necessary. A quick visual inspection for any glaring defects, and bullets that are within +/- 2 grains, will get you groups that are accurate and impressive.

An additional note: going through the effort of sorting and selecting the best bullets really won't do much for you if you don't also put in the due diligence on case preparation and load development. I don't weight sort my cases; for target work I just select brass from the same manufacturer (and same year for military brass). But I do use neck sized only, trimmed to length brass that has had both the inside and outside of the case mouth de-burred. Also, you'll need to do some load development to discover what powder works best with your load. My recommendation is to start out with the quicker rifle powders like 2400, IMR-4227, IMR-4198, AA-5744, shooters world buffalo, or Rel #7. Not always, but usually, heavy for caliber bullets work best in target loads. Best accuracy is usually with either a Loverin or bore rider design; I prefer bore riders, but there are a great many better shots than me who shoot Loverins. Searching for better accuracy is just one of the many things that makes casting bullets a fun pastime. It's just as rewarding as bringing home the game with a bullet that you made yourself, or spending a fun day at the range with friends shooting sacks full of ammo that are better than, and cost a lot less than, stuff bought at a store.

[huntinlever]

I'm wondering if I need to go back to inspection, weighing and sorting. Through the first few sessions on a new mold I accepted within 1% variation or 4 grams on a 400 gr bullet, and all bullets I sampled, so long as they visually checked out, fell within that range. I figured, good enough for hunting a 45-70 at all reasonably expected ranges, certainly not a BR or even bottleneck cartridge for longer distances.

Since then, I go on visual inspection only and discard any obviously bad ones (deformed from dropping, fill out issues, rounded shoulders, finning, etc.), or any with any wrinkling of any kind on the (don't know what they're called - the portions of the seated bullet that contact the barrel's lands, the ridges between the lube grooves). I'm pleased with my groups, which currently are tight through development and confirmation range trips - getting from sub-MOA to 1-MOA. Though I admit flaws would probably be much worse at longer distances.

That said, seeing the tolerances you guys implement brings me to wonder if I could be shortchanging good bullet possibilities.

[quilbilly]

I do random weighing. If all the boolits are within 1-1/2%, the batch is good to go unless I see one obviously deformed. With my old eyes, I am not good enough to know the difference with iron sights or scopes 4-6X.

[charlie b]

If I was going down this road, I would put the work into determining how much of it actually matters, and to what degree....

That is precisely what got me to the point I am at, sorting down to 0.1gn and using the heavier bullets for precision.

When I started I did not weigh the bullets, just inspected. Results were OK but not great. 3MOA or so. Then I started weight sorting to 0.5gn batches. I also was not casting very consistently at that point. That got me down to about 2MOA. Then I went to 0.3gn batches. That number was chosen based on my weighing a bunch of Sierra Match King 168gn and 155gn Bergers. They were all at the weight or 0.1gn high or low, eg, 167.9 to 168.1gn.

I was still getting fliers that made my groups average 1.5MOA. So, I then went to sorting at the 0.1gn level. I started getting more groups at or less than MOA and fewer fliers.

So, yeah, my data backed up my choices.

[ACC]

When casting bullets for high performance rifle loads, what weight consistency do you shoot for? For instance, I'm casting 30 cal bullets using the 170 gr Lee FP and 180 grain RCBS FP right now. When y'all do such casting, what weight consistency (+/_ X.X grains) do you strive for? Or maybe it should be expressed in terms of percentage because of the wide range of bullet weights we cast....

When I cast for my 7.62X39 I stick with +/- 1 grain. It allows for 1 to 1.5 inch groups at 100 yards.

ACC

[Larry Gibson]

Another response, pertinent to this thread post about 6 years ago.

Larry,

Those are some nice groups. With regard to consistent boolit weight, what do you consider consistent? Plus or minus X.X grains?
It depends on the weight of the cast bullet to begin with. Most weight sort thinking those bullets that weigh the same or with a +/- will shoot the best. I've learned that while that method of selection will give better accuracy it will not give "the best". As I weigh each bullet I visually inspect the bullets first. Any visual defect, no matter how small, is cause for rejection. I then weight sort to eliminate those very light bullets that passed the visual inspection but obviously have a void inside. I then put the bullets into small plastic bowls of .1 gr increments.


I'll explain with 7mm to 32 caliber bullets of 150 to 220 gr as an example. Many who weight sort will kind of "graph" the bullets out by lining them up in tenth grain increments that are consecutively numbered and straight across the bottom. What you end up with is a "bell curve" shape of bullets. The curve starts out curving up, peaks out and then curves back down almost the same as it went up. The majority of the bullets in the curve will have a 1 to 1.5 grain difference in weight. There will be some that are much lighter and a few heavier. That is what you get with "good" cast bullets.

Using a quality alloy that will cast excellent bullets is also paramount. This is why straight linotype and #2 alloy are most often used. They give excellent and uniform fill out, consistency of weight with fewer defects. Some batches of COWWs will also if the antimony and tin percentages are sufficient and balanced. Alloys in these smaller caliber bullets that give a lot of shrinkage will never cast "excellent" bullets no matter how good they look. The reason is we cannot control the shrinkage and where it occurs on each bullet. Slight shrinkages that are in different places on the bullet are undetectable by visual or even precise measurement and they mean a slightly unbalanced bullet. Might not seem like much but at higher RPM and/or at longer ranges of 200 yards and beyond it is readily detectable on target by enlarged groups and poorer accuracy. Complete fill out in the mould and minimal shrinkage is needed for a quality cast bullet that will give the best accuracy.

Weight sorting the visual inspection passed bullets with "excellent cast" bullets gives a weight sorted curve that rises sharply and then levels off with several weights (three or four of .1 grain increment) having about the same number of bullets. The curve then falls sharply to just a few heavier bullets. There is no downward "curve".

When I got the 4 cavity NOE 30 XCB mould I ran this test with Lyman #2 alloy;

I cast 531 bullets

1.9% were rejected for visual defects

8.6% weighed less than 157.7 gr (some as much as 2 gr less that obviously had internal voids I could not detect through visual inspection)

3% weighed 157.8 gr

4.5% weighed 157.9 gr

5.9% weighed 158 gr

18.7% weighed 158.1 gr

19.3% weighed 158.2 gr

21.6% weighed 158.3 gr

14.7% weighed 158.4 gr

1.8% weighed 158.5 gr.

I then loaded 10 shots of each increment (157.8 gr to 158.5 gr) to test at 300 yards.

Test rifle was my 30x60 XCB. The NOE bullets weight 164 gr +/- when fully dressed and were loaded over 53 gr of AA4350 which runs 2900+ fps out of that rifle. The incremental test loads were fired consecutive by weight with the barrel cooled, cleaned and then fouled with 2 fouling shots prior to the next increment test. The results were then graphed out for a simple visual comparison.

313508

We see the lighter weight 157.8 and 157.9 gr bullets were not as accurate. The lighter weight bullets giving indication to probable incomplete and inconsistent fill out and/or shrinkage or that they have small void(s) in them. The "heavy" end of the bullets (158.0 through 158.5 gr) gave consistent accuracy (precision) at very close to moa at 300 yards. I have run this test several times and with cast bullets in the 150 - 180 gr weight range I select the heavy end of the weight sorted bullets +/- .2 to .25 gr. With this weight range I use the 157.8 and 157.9 gr bullets for foulers and the 158.0158.1 bullets for sighters. The 158.2 through 158.5 are then used in matches and other tests where precision is measured. For the best accuracy at this level of high velocity the top half (158.3 to 158.5 gr) of those selected bullets almost always give the best results, particularly at 200 and 300 yards.

With other weight ranges I like wise run a similar weight sort test and now select the heavy end of the match selected weight sorted bullets for accuracy/precision use.313509

[racepres]

^^ Yup...the Bell shaped from weight sorting is evident... Generally I pitch the two ends back in the Pot... the rest...depending on intended use... I generally throw em together and Load..

[405grain]

The meticulous visual and weight sorting is for loading the precision rounds that I use to try to push the envelope, and see what's possible with a given rifle, (also to push myself and see what I can do). All the bullets that pass the visual inspection, but are too heavy or too light, I load those up too. Yes, they will shoot a bigger group, but the position of the center of that group doesn't change. It's a lot of work making those "perfect" cast bullets, so I don't want to waste them on sighting in, powder and load development, or general practice. If I'm shooting a 4" group at 100 yards with powder "A", and a 3" group with powder "B", then I know that B shoots better, even if I'm using bullets with a larger weight spread. Picking off used Gatorade bottles full of water, or soda cans, is a great way to practice shooting offhand, but I don't need super high precision bullets for that. It's nice to have a batch of bullets that are as well formed and balanced as can possibly be made, but to keep shooting and reloading fun "Don't let perfect become the enemy of good enough".

[huntinlever]

"Don't let perfect become the enemy of good enough".

I've started another thread related to this in a way, then read your post. I'm going to burn this one in.

[charlie b]

That is a good thing to keep in mind.

I have gone 'down the rabbit hole' looking for more precision. Not quite all the way though. :)

From all my time behind a scope I just do not believe I am capable of consistent groups much smaller than 1/2MOA, so that is my 'good enough' with jacketed. I'd love to get my cast bullets to that level, but, I am really happy with groups just around MOA. I am just not as consistent with it as I'd like to be. Some of that is due to my shooting ability, some due to loading practices, and some due to casting practices.

And, yes, I also keep some of those 'not so good' bullets for fouling and warm up shots.

[Larry Gibson]

"And, yes, I also keep some of those 'not so good' bullets for fouling and warm up shots."

No reason not to use those bullets if fouling and warm up shots are/can be taken. In local cast bullet matches I don't even put them on target (sighter target) but just put them into the berm just off target.

[racepres]

Really causes stress when a few that were Culled...shoot a Darn Group tho!!!
Proof that I need to keep better records!!!!