Weight Deviation in cast bullets

[standles]

All:

Just a curiosity question for you other anal casters [smilie=1:


I have a batch of alloy. I cast 200 bullets discrading obvious imperfections and randomly sample 50.

What weight distribution from the cats wt would you expect?

+- 1 grain or more ?


Reason I ask is I did this and found the bell curve centered around the 520 grain mark but had excursions +- 5 grains and flyers out to +- 10 grains


trying to use this to improve my casting technique and pick the cherry ones for competition shooting.


Steven

[racepres]

I will assume [I love that word] that you meant 250 gr.. but, no matter.. for me anyway , it is a percentage thing.. so by my random method, a deviation of +/- 2.5 gr would be acceptable to me w/ a 250 gr boolit!! I use 5% either way for "Serious work"! Or 10% total and feel that 10% either way [20% total] is just fine for "plinking" HTH.. MV
BTW sometimes I admittedly don't weigh at all!!! Just visually inspect and go... Works fine for ringing steel!!!

[felix]

Steven, in the boolit world of BR accuracy you would need zero weight variation between boolits in a batch to consider them match quality. A half grain above should be put into another pile; a half grain below should be put into the other. The reason is that you do not know where the micro- air holes are on a per boolit basis. Jacketed bullets, carefully hand crafted, can vary a full one or two percent in weight and still be reliable in performance. However, the person doing the swaging must pay their utmost in attention to how the bullet feels during the swaging operation. ANY difference in feel from the new lot being made, that bullet would go into the VARMINT sales pile, and not into the BR sales pile. ... felix

[Johnw...ski]

Hi,

I have noticed the same thing with some .458 boolits I have been casting.
My 405 gr. Lyman mold is throwing boolits between 400 and 410 gr. with no obvious defects. Some bought cast boolits that said 480 gr. on the box are weighing in at 505+ gr. (my scale only will go to 505 gr.) and some down to
490 gr.

I had never given it much thought before, but a rifle I am currently trying to shoot for groups from a bench is giving me fits. I have segrated the boolits by weight and it helps but is not the whole answer, for me anyway. The .458 sized dia. has worked in past rifles I no longer have and even seems to work in my .458 Win. Mag. but who wants to bench rest that? My next step is to try sizing the boolits to .459, .001 over bore dia., probably what I should be sizing them to anyway.

I realize consistancy is the name of the game but I am not convinced that I need to weigh each and every boolit I cast.

Years ago I knew an old gent from the range who shot an old high wall in 38-55,
(he sold me the 45-70 barrel from it because he couldn't take the recoil anymore), bench resting on the 200 yd. range. He had one 38-55 case, he would
hand decap the primer and install a new primer with a hand tool, take a scoop of powder (smokeless), cover it with a cardboard disc cut from his cornflakes box,
take an as cast lead boolit apply some sort of lube with his fingers, partally push it into the case and seat it against the rifling when he loaded the gun. He could shoot 1" groups at 200" yds all day with that set up. I am certain he wasn't weighing his boolits.

John

[Harry O]

You might want to work on reducing the spread. I have found out that running the melt hotter (which means my casting speed is reduced) usually reduces the spread for me. I believe it reduces the internal defects (bubbles, cold laps, etc). I have decided the slower speed is worth it. I have weighed some batches 100% and found that I can usually have a spread of 3 or 4 grains (total) on a 180 to 210gr bullet. I have about half again more than that on a 400 grain bullet. In most cases, there is very little heavier, (say one grain) with most of the variation downward.

I visually inspect ones and remelt those with obvious external defects. I have (in the past) looked at them after they cool, but before sizing and lubing them. However, that is usually not very productive. Any more, I wait and visually inspect them after lubing and sizing. Any surface defects will stand out with lube.

[standles]

Thanks for the replies so far but keep them comments coming. I learn from each one.

Yes it is 520 grains (45-70 butt thumper).


My problem was my curiosity. Now that I have done the weighing it is a nagging mosqiuto in the back of my mind. I thought I divirced my nagging problem years ago :drinks:


Out of my random sample I had 2 that measured exactly the same. If I take into account the Tolerance of the scale I could lump a few more in.


I run the cast at 750 per the RCBS thermometer.

My next step is to throw the marvelux away, clean the crud out of the pot and start new. My thoughts being inclusions I cannot see. I need to get the marvelux residue off anyway and this as good an excuse as any. :mrgreen:

Think I will switch to some old 50/50 lube I have or maybe some oiled sawdust.

Steven

[VTDW]

standles,

A friend and fellow CB member here does extensive reloading and testing of several different cast boolits. He did a write up on another forum detailing that his testing showed that up to 8 grains difference made no significant difference in POI. I am confident that he meant for hunting purposes though. I am sure benchrest shooters and the super anal will violently disagree. I pay no attention to weights of my cast boolits dropping from my molds using my alloy any longer and still am able to shoot sub MOA fairly regularly with no wild fliers.

Dave

[felix]

Weight difference is not the problem. It is the locations of the missing weights that are the problem. ... felix

[Johnw...ski]

Weight difference is not the problem. It is the locations of the missing weights that are the problem. ... felix


I have to agree that is exactly right, and a bigger dia. makes it worse as the boolit spins.

John

[racepres]

So my % assessment is flawed?? Whoda thunk? Luckily I don't cast larger than 35 cal for anything except handguns just now, and I don't weigh Handgun Boolits very often.. and when I do I am a "Liberal"!! My method works good enough for what I am doing.. but I can certainly see the Point!! MV

[boommer]

I find too that if run my pot hotter just to the point they start to frost if I cast too fast and at that heat level it stays molten long enough to lightly tap mold handles to settle it sometimes you will see the sprue drop a hair. I do get sharp edges and very consistent weights. just slows down casting speed but I only do this with rifle bullets, pistol bullets not so worried about weight.

[freedom475]

I cast a 500gr spire Lee for my 45-70 sharps...While weighing the booltis for match shooting I found that my RCBS scale can't be trusted that far out on the scale bar. I can weigh the same boolit several times and get different weights:confused: I wished I would have figured this out before I hand weighed and seperated over a 100 boolits:mrgreen:

[Bass Ackward]

standles,

A friend and fellow CB member here does extensive reloading and testing of several different cast boolits. He did a write up on another forum detailing that his testing showed that up to 8 grains difference made no significant difference in POI. I am confident that he meant for hunting purposes though. I am sure benchrest shooters and the super anal will violently disagree. I pay no attention to weights of my cast boolits dropping from my molds using my alloy any longer and still am able to shoot sub MOA fairly regularly with no wild fliers.

Dave


Dave,

Yep. My work too if you shoot cast at what are thought to be cast velocities and cast pressures. The faster in velocity you want to go or the faster twist rate you are forced to run, the more pressure you will be applying. So you better have solid bullets to do it or that base is going out of square.

Once that happens, you will get wild action that will be blamed on everthing under the sun. :grin:

I found that lubing and then sizing down from one caliber above using a nose first sizer to support the base made stronger bullets for the caliber below than molding them in that diameter. This negated the weight differences.

[BABore]

Weighing bullets, and collecting any meaningful data is only useful if your working with a single cavity mold. Even then you have to make the ass-u-ption that you held the blocks together tightly on each and every cast.

With multi-cavity molds, cavities are very seldom exactly the same. To make weighing bulets any use at all, you need to measure them at several places with a micrometer first and segregate the sizes into lots. Now you can weigh them and sort into final lots. Only the heaviest of each lot can even be considered to be near perfect.

A bullet that runs on the small side of the curve, and has no internal or external voids, may weigh the same as a bigger bullet with voids. There's no way of telling this unless you measure them first.

If you going to be anal, might just as well do it right.:-D

[Bass Ackward]

Weighing bullets, and collecting any meaningful data is only useful if your working with a single cavity mold. Even then you have to make the ass-u-ption that you held the blocks together tightly on each and every cast.

With multi-cavity molds, cavities are very seldom exactly the same. To make weighing bulets any use at all, you need to measure them at several places with a micrometer first and segregate the sizes into lots. Now you can weigh them and sort into final lots. Only the heaviest of each lot can even be considered to be near perfect.

A bullet that runs on the small side of the curve, and has no internal or external voids, may weigh the same as a bigger bullet with voids. There's no way of telling this unless you measure them first.

If you going to be anal, might just as well do it right.:-D


Yea, your thinkin. What happens if you size them first?

[BABore]

You elongated the larger diameter bullets more than the smaller ones. That is of course unless your sizing dies look like a cheese grater and your actually removing metal through sizing. If your thinking that the sizing helps collapse the internal voids, it probably does to some extent on those close to the surface, but it's a best guess "I hope" situation.

[mroliver77]

Mebbe I am doing something wrong. I just cast a pot of .310 180gr LBT from a 2 cavity mold. I was weighing them after visual inspection with magnifying glass. 90+% were within 1 gr
I find an average weight and anything above or below .5gr going into the plinkster pile. Most everything that fails this apon reinspection I find usually it is from molds not being tight or a wrinkle I missed.
I do cast very hot using the Bruce B method or one akin of it. For my type shooting(hunting, plinking and some paper) this is probably more work than needed but in working up accurate loads I like to remove what variables I can.
Now for the .22 cast!! Jay

[sundog]

BABore, that might be right for a custom gun, but for the normal run of the mill guns many of us shoot (mass produced chambers), I see things a little different. Here is one example. I have a 6 cav SAECO #301 that for all purposes I have drop boolits the same size (very well made mould). Weight segregated, they will consistently shoot in the 295+/300 range for mil bolt matches from a rack grade 03A3. Without weighing, occasional flyers show up pushing the score into the 290- range. I've had this mould long enough and shot enough matches with the boolits from it that I know that what I am saying correct.

Will this always be the case? Maybe not. A match chamber and barrel would certainly make a difference.

[BABore]

I wouldn't really know about the custom guns as I don't own any. Just scoped hunting rifles. About the closest thing I have is a T/C Encore with a Bullberry 338 Win Mag bbl. That one will easily do 3/8 to 1/2 inch 3-shot groups. My E.R. Shaw barreled 375 H&H will shave an 1/8" off of that. All my other stock factory guns go from 1/4 inch to 1 inch with their preferred loads. Most of these are lever guns.

I only get serious and mic and weigh bullets when I'm testing a new bullet design for load developement, or in cases of extreme boredom. If the bullet fits the rifle's throat/bore properly, and your using the right alloy for the task, you don't have to fret the small stuff too much for general shooting.

[Bass Ackward]

You elongated the larger diameter bullets more than the smaller ones. That is of course unless your sizing dies look like a cheese grater and your actually removing metal through sizing. If your thinking that the sizing helps collapse the internal voids, it probably does to some extent on those close to the surface, but it's a best guess "I hope" situation.


Yea. My point was that you eliminated the size variance and took it to a weight only issue. But I don't like to weight bullets either.

This was why sizing was considered bad for accuracy years ago with lubricisors. Nothing was there to control the base from elongating outta square. Which is why nose first sizing is superior too.

[sundog]

BABore, yup, FIT. I can't agree more. And appropriate alloy.

I've related this story before, but one more time won't hurt. A few years ago I had a bunch of boolits just cast and noticed a black spec on the base of one of them. Hmmmm, says I. On closer inspection it was not a spec but a pin hole leading to a small void. Several more from that batch were the same way. I had been weighing match boolits for quite some time, but that incident with the pin hole cinched it for me for weighing boolits for purposes that needed weighing.

Besides fit, the other thing that is absolutely required is a good base, GC or not.

[1Shirt]

Being at best a marginal handgunner, with handgun bullets, I discard the obvious flaws, size, lube and load the rest, and blaze away. For me weitghing handgun blts. would be a waste of time. On the other hand I am very picky about rifle blts, and use the following rules after discarding the obvious flaws.
1. For 22 Cal, I seperate by exact weight. A pain, but it pays in accuracy for me!

2. For 6MM, to within .3

3. For 6.5 and 7MM, to within .3

4. For 30 to .3 for most grneral shooting, to exact weight seperation for match loads.

5. For 37-45 to .3-.5

I am sure that there will be those who disagree with my standards, but my standards work for me.
1Shirt!:coffee:

[JSnover]

1Shirt,

Just so I'm clear, does that ".3 -.5" mean 3-5 tenths of a % of the total weight?

.5% of a 400 grain bullet would be a deviation of 2 grains, or an allowable weight of 398 to 402.

Not questioning your method, just making sure I read it right.

[Harry O]

Weighing bullets, and collecting any meaningful data is only useful if your working with a single cavity mold. Even then you have to make the ass-u-ption that you held the blocks together tightly on each and every cast.

With multi-cavity molds, cavities are very seldom exactly the same.

Correct. I had two single cavity moulds that cast 11 grains different out of 400 grains. Another two SC moulds were about half that on 185 grains. I have cast and measured the two cavities of a two cavity mould a few times and found that the difference we a good deal less -- usuallyt less than one, but never more than two grains out of about 200 grains.

[BABore]

Yea. My point was that you eliminated the size variance and took it to a weight only issue. But I don't like to weight bullets either.

This was why sizing was considered bad for accuracy years ago with lubricisors. Nothing was there to control the base from elongating outta square. Which is why nose first sizing is superior too.


You kind of missed my point somewhat. By segregating the as cast bullets into lots based on diameter (measured on key features), then weight sorting these lots, you catch the internal voids mo-better. If you size them all first, how can you tell the difference between a perfect void-free bullet that's say 0.3105 verses and larger 0.3112 bullet with internal voids. They may well be identical weights.

Now technically you can if you measure the OAL after sizing, cause the larger diameter bullet will elongate more. But, what if the size difference shows up in a BR nose portion that doesn't get sized? I agree that some weight variation will make diddley squat difference. It's the voids that will get you and this is the best method I've found so far. None of this addressing the root problem, how they get there in the first place.

I ladle pour everything and only cast for 30 cal and bigger. Usually from a WW-Pb alloy around 50/50. I normally don't use any tin and seldom have a real need for it. Every once in awhile, like every 6-8 months or so, I'll get the stupid notion I just gotta add some tin. Everything turns to chit and I get nasty,dirty looking slag inclusions on the outside of the bullet. I can only imagine what the insides look like. While lighter than lead, these inclusions are not air pockets. Too much tin will spoil the soup.

I've found that true air pockets are mainly caused by either pouring technique ( force, rate, and size of the flow), or mold venting. Either though turbulance or choking the sprue hole your going to trap air if it can't get out quick enough. Alloy temperature plays a big hand in this.

If you can eliminate most of the causes of voids, weight variation will go down. To reduce it even further you have to run a tight control on your alloy and mold temperature. 45 2.1 educated me on the technique of using a high speed fan to cool the sprue and then after dropping, cooling the open mold blocks. It has to be done in a timed rhythm that's dependent on alloy temperature and bullet/mold block needs. Once the sequence is established, it's relatively easy to cast 400+ grain bullets with less than +/-0.2 grains total variation. This is with multicavity, cherry cut molds.

[shaggy357]

I use a lot of cast bullets when shooting silhouette out to 500 meters. When I am sorting my bullets I class them similarly to the way 1Shirt does. My 7mm and 30 cal bullets are put into cups by .5 grains. This means that 149.0 to 149.4 goes into one cup. 149.5 to 149.9 goes into another cup. 150.0 to 150.4 goes into another, etc. Most of my bullets will show up in three or four cups. Ones in cups on either side are used for plinkers or just fun shooting. Sometimes I do save them until I can load up a box of 100.

When weighting my 357s, 41s, 44s, etc. I put them into cups within 1.0 grain. 210.0 to 210.9 goes in a cup, 211.0 to 211.9, etc. Again, most will fall within that 3-4 cup space.

My buddy does most of the casting for me. He will cast his bullets and will keep them exact weight only. If he deviates more than a few .1 of a grain, he re-casts the bullets. Our scores are usually pretty similar with the bigger calibers. I don't know if he has an exceptional 7mm or what, but one of his 7mmBRs does phenominal with a Saeco 160 cast bullet.

Good luck and shoot straight.

Steve :)

[Bass Ackward]

Exactly. That was the logic I was looking for. If you mold with a proper technique and temperature, then you don't experience voids. Which is why I don't weigh. If you mold patiently enough, you don't have diameter issues either.

I never cool the sprue first or the plate, because that is the sourse metal for filling the cavity. I want the sprue to be the LAST thing that solidifies so the bullet can draw what it needs. But properly vented molds almost never have a voids if your temp is even close to right. And my thermometer keeps me straight there.

As a side barb, I have shaved up to 5.0 grains off a nose of 250 grain, 35 caliber bullets and still shot 1 1/2" above 2000 fps. That's .02%. So .5 grain isn't a make or break deal for me.

Glad you enjoy such success with your rifles!

[BABore]

As a side barb, I have shaved up to 5.0 grains off a nose of 250 grain, 35 caliber bullets and still shot 1 1/2" above 2000 fps. That's .02%. So .5 grain isn't a make or break deal for me.

Was that at 300 yards, or did you have to wipe the powder burns off?:-D

Yep, you got to have a good sprue and patients. If the mold and alloy are right, I look for a 3 second freeze time before I move the mold. Then it gets the fan treatment for a timed count. Dump them and hold the open mold in the breeze for a timed count.

[1Shirt]

JSnover, Correct on the big ones. I just don't see that much difference in accuracy on the big ones at the ranges that I shoot.
1Shirt!:coffee:

[felix]

"He will cast his bullets and will keep them exact weight only. If he deviates more than a few .1 of a grain, he re-casts the bullets." ....

That is the way you are supposed to do it for BR. Now seperate those into 0.1 buckets. ... felix

[texas tenring]

I have noticed that my shiney pretty boolits are generally the heaviest and if the mould gets hot and boolits begin to frost those boolits are consistantly lighter. I have not thougth to measure them but I bet the diameter would be different also. I will measure and report.

The only thing I hate about casting, is weighing and segregating boolits but I try to do them all.

[hyoder]

Saturday I dropped 308 bullets, after visual culling very few while casting, from a Lyman 311419 two cavity mold. 300 of these had a total spread of .6 gr. this was with an approx. #2 alloy at 775 degrees.

When I was casting 45-70 bullets for BPMC Silhouette I would normally get 450 to 500 gr. bullets to drop 90% plus of the bullets +/- .5 gr. casting 20:1 lead:tin at 850 degrees with Lyman, RCBS or Saeco molds. I use two molds to maintain a rythem and give the molds cooling time.

I ladle pour from a Lyman pot - never was happy with bottom pour results.

My alloys are made up in 100# batches and include some chilled shot for a little arsenic - which I believe along with the right tempeeratur is the key to consistancy.

I am somewhat particular about degreasing and cleaning molds for each casting session. Other than that I don't do much special and don't have any problem getting fairly consistant results.