Powder ? how important is a .1 of a grain ?

[gray wolf]

I had to use a friends scale and I find it different than my old 505 RCBS.
His scale is very accurate, measures to .02
I had made some sample weights to match my loads and they were always perfect with my scale, or at least that's what I always went by.
If I used 51.5 grains of IMR 4831 for my 270
I made a sample weight for it. I would zero my scale and place the sample on it and it would read 51.5 ( always ) I would then weigh my charges .
On the different scale I find that my 51.5 is 51.6, so I take it to say that my old 51.5 was really 51.4--I hope that makes sense to everyone.
His scale and my old check weights below 15 grains seem to match fine.
The error comes as the weight goes up. 75 grain weight measures 75.1
I need 74.9 to get 75.
What would make a scale want to clime up .1 of a grain as the weight increased ?
So how much drama is wrapped around .1 of a grain.

[cbrick]

Your scale is reading well within the mfg claim of plus or minus 0.1 (one tenth of a grain). I haven't seen any common reloading scale claim better than that.

As to how much difference this will make look at it as a percentage of the whole.

One tenth of one grain in a 3.0 grain charge is roughly a 3.4% variation. (might make a small difference)
One tenth of a grain in 75.0 grain charge is roughly .13% variation.

It's doubtful that a rail gun could tell much difference on target with 74.9 or 75.0 charges.

I don't see any problem with your scale, use & enjoy.

EDIT to add: If scales were made were every one was exact at say 75.0 grains (being that precise) very, very few people could afford to buy one>

Rick

[Ugluk]

1/10 out of 75 would be 0.13%.

Using a fast powder in a 9*19 I guess it could make a difference.

[cbrick]

1/10 out of 75 would be 0.13%.


Dang it, who moved that decimal point on me?

Not surprising though, I have trouble even spelling math. :roll:

Rick

[1Shirt]

How important to me means size of case, and not overly important in rifle cases above hornet. However in small pistol ctgs, 1/10th could be the difference between a max load, and an excessive load with powders like bullseye.
1Shirt!:coffee:

[onesonek]

Dang it, who moved that decimal point on me?

Rick

The 3T's stike again Rick :killingpc

[deltaenterprizes]

In rifle charges not much, in pistols a little.

[onesonek]

"So how much drama is wrapped around .1 of a grain."

Not very much at the pressures we normally associate with cast. When you push the pressure limit of the particular rifle load combination, then you will see more effect.

On side note, I use check weights and zero the scale as close to the the charge weight. As you found, when I go below or moreso higher than the checked weight, the more variation I get. So it imo, you'll be fine with your load work above. If you use another round or powder that goes over 60 grains, use a 60 grain check weight. I go in 10 intervals with check weights,
on my general loads. For long range target work much less.
As Rick said, the typical loading scale we use, isn't like a precision scale costing 1000-2000 dollars.

[uscra112]

More important as you get close to the pressure limits. Especially so with faster powders.

Saying that a scale is "accurate" means that it has been calibrated by some method traceable to a national source such as NIST (in the USA) or PTB (in Germany). Is that true for the "friend's" scale? It's not at all uncommon for two measuring instruments to disagree, and only comparison with a known good instrument can resolve the argument. Hence the existence of those "check weights" you can buy. (And the traceability is why they are so expensive.) Maybe the OP's scale is the more accurate one! (Resolution to .02 grains has nothing to do with accuracy!)

I for one will not use electronic scales - they can and do "drift" too much and too fast. It's also true that electronic scales are usually accuracy-rated by stating the average error as a percentage of the displayed value. 1% is typical. That's a small amount when the load is 5 grains, but almost a full grain if the load is 75 grains. If you insist on using electronic scales, making up a check weight as the OP did is a very, very good idea.

Sorry to be so long-winded, but I spent a career doing precision measurement, ending up at Carl Zeiss, one of the acknowledged world masters at metrology. It's a subject near and dear to my heart.

[gray wolf]

Thanks men --Some very good opinions and advise.

Sam

[44man]

Thanks men --Some very good opinions and advise.

Sam
Slow powder in a revolver? I don't even fool with less then 1/2 gr.
Fast powders like Bullseye and you might want to.
Rifles with slow powders, a drop of water in a 50 gallon barrel!
I really laugh at the guys that say 23.7 gr of 296 in a revolver is good but 23.8 is no good. Temperature changes outside can change that a whole lot more.
4831????? That would be one or two pieces of powder.

[nanuk]

I think it was Barsness who tested this out....

powder, boolit weight, and perhaps something else

it comes down to so little difference that you cannot hold well enough to know

[btroj]

So you are actually shooting 75.1 gr instead of 75. Does it matter? I don't care as long as 75 gr is always 75.1. I want to know that the same object always comes up the same weight.

This is an instance where precision is more important the accuracy.

[mpmarty]

Just proves a man with one watch knows what time it is. A man with two watches is never sure. My 270 load with 130gr bullets was always 60gr of H-4831

[kelbro]

So you are actually shooting 75.1 gr instead of 75. Does it matter? I don't care as long as 75 gr is always 75.1. I want to know that the same object always comes up the same weight.

This is an instance where precision is more important the accuracy.

This is what's important.

It wouldn't matter if your scale was .3 or .6 off as long as you worked your load up properly. What matters is that you can repeat that load.

[geargnasher]

Here's my take on the whole deal: If your load is good, it will tolerate at least 1-2% deviation in powder charge weight without significant loss of accuracy or wide swings in point of impact. After all, that's what really matters, right? If your load is on the edge of pressure or accuracy windows, I think more experimentation is in order rather than splitting hairs to the second decimal place with lab-grade equipment. As long as your scales are calibrated and reasonably accurate/repeatable, that should be good enough for 95% of us.

Gear

[turbo1889]

As to the question asked by the OP as to why the two scales would agree with each other in the lower range of the measurement spectrum and disagree with each other in the upper end.

You need to realize that the terrestrial gravity field is NOT a stable continuous constant. It is true that the universal gravity constant applied to atomic mass is a constant unit but the local gravitational field at or around the earths surface does vary slightly depending on your exact location and elevation.

In the metric measurement system which is the standard used by the scientific community the force of the local terrestrial gravity field normally varies between 9.800 m/s^2 to 9.810 m/s^2 and thus the local variance shows up in the third decimal place or fourth significant figure.

Long story short since scales measure weight not mass and weight is the product of mass and the local terrestrial gravity fields force on extremely precise scales the exact mathematical relationship between mass and weight needs to be calibrated to the specific location where the scale is located for it to be truly accurate. Two scales may both be exactly accurate at a specific weight but as you add more mass the weight they display can diverge from each other depending on exactly what constant they are programmed with (9.803 versus 9.806 for example). The most precise scales have a series of check weights and a built in calibration program that allows you to calibrate the scale to your local gravitational field. I have a jeweler’s scale that is set up exactly like that with two different check/calibration weights one significantly heavier then other and by calibrating the scale at two different points with the two different weights the scale can determine the correct constant to use for a specific local field strength.

A lower quality scale, even those with a calibration program that only uses a single check/calibration weight, assume a stable unchanging constant to perform the internal calculations. Usually that is a compromise and is at or about 9.805 m/s^2 or so.

[**oneshot**]

So long as your scale is weighing the same everytime. I throw most of my charges so a .1 variance is common with some powders I use. I shoot target comp and have never really noticed a difference.
The only round I reload for that is really noticeable with any variance is my hornet. I trickle those.

[Cap'n Morgan]

I'm pretty sure the LOT to LOT pressure variation for most powders is more than you would see from a +- 0.1 gr variation in your 51.5 gr 270 load. For what it's worth I never bother using decimal increments for any loads over 50 gr - just whole numbers. Also, I never venture into the red zone pressure wise. All the flat-shooting hype I succumbed to when younger, pretty much lost its meaning when the laser rangefinder appeared on the scene.

[rbertalotto]

It wouldn't matter if your scale was .3 or .6 off as long as you worked your load up properly. What matters is that you can repeat that load.

This is why Benchrest shooters don't weigh charges. They use "clicks" on a culver type powder measure.

Being consistent with powder weight has been proven to have zero effect on accuracy. Powder VOLUME is much more important.

Weight is specified in loading manuals as it is easy for reloaders to understand and interpret. But volume will get you accuracy.

It cracks me up when I hear of rifle shooters using the new computerized powder measure devices that trickle in the last .001g of powder. I wish they could understand that there are logarithms in all these electronic devices that finalize the measurement. Only in a controlled environment can you expect the accuracy that lots of these digital scales purport.

A few years ago I did an experiment with a 270 and a 338WM. I shot with a large white sheet spread out in front of my shooting bench. After each shot there was lots of residue on the sheet. After a few hours of shooting there was LOTS of residue on the sheet. I gathered it all up and put a match to it. Sure enough, it was unburnt powder. the 270 had a 24" barrel and the 338 a 26" tube. Just shows to go ya that we aren't burning all the powder we load anyways.

Always fun.....................

[Sonnypie]

If you were selling gold, it might matter.
But you are looking for your most accurate load.
And who is to say you are actually getting 100% burn, 100% of every shot?
Ever look down the barrel and see any flecks of unburned powder? Yep.
Now think back on your trickeler and how a few grains or flecks made that beam move 1/10th of a grain.
If it is that bothersome to you, zero your scale 1/10th lighter. :idea:
There, I fixed it. (BTW, my 5-0-5 scale sez Lyman on it.)

I, too, am very demanding of my loads. I want to remove as much human error as I possibly can. That is why we reload, to do a better job and KNOW what we are shooting.
But we can NOT remove very slight variances (tolerances) in the components we use.
If you want to worry, consider primer function, flash hole uniformity, case neck tension, case uniformity, and check your barrels harmonics. :veryconfu
And remember every shot changes the fouling in the barrel. :rolleyes:

Just load as close as you can to your personal recipe.
And then don't worry about a fly fart at 123.7 yards changing the trajectory of your boolit on it's 234.1 yard flight to your intended point of aim. ;-)

Relax. Shootin is fun.
(Daniel Boone didn't really stack those balls in the movie, "Davy Crockett.") :-(

[gray wolf]

Well I must say that I do agree with just about all the great responses.
Great to know that my fellow reloader/casters know so much about a subject
not always talked about.
Let me add I always go for consistency and never hot rod my loads.
If my scale matches my sample weight for that load I am good to go.
I am very rarely near the top end. I do exhibit a degree of cautiousness
with Julie's 32 ACP loads, but I go back to my sample weight ( home made )
for that load also.
I was just curious as to why the scale would show a different weight as the mass weighed got larger.
I fully understand the explanation and thank you.


GW.

[Shiloh]

I don't have a firearm precision enough to tell. Couple that with this shooters eyes and it become impossible to tell.

I have had differences with half grain changes, but never really tuned more than that.
Wish I had the time back, less the frustration from fretting about ultimate accuracy.
Yeah, I want accuracy. But trying to get the utmost accuracy from firearms incapable of delivering it, was frustrating. Would Be nice to try it with a tight tolerance precision rifle. Be nice to have the money but more importantly, the time to experiment.

Shiloh

[mdi]

Wow! I never considered gravity variations, but it sounds plausible. I have read here and other sites that a 2% variation of powder isn't noticable as far as pressure and accuracy are concerned...

[918v]

How important to me means size of case, and not overly important in rifle cases above hornet. However in small pistol ctgs, 1/10th could be the difference between a max load, and an excessive load with powders like bullseye.
1Shirt!:coffee:

No it wouldn't.

Scales are not that consistent as to be within .1 grains of eachother. Published data takes that into account.

Bullseye is not an evil volatile nuclear explosive, even with max loads in the 9.

[rbertalotto]

I'm pretty sure the LOT to LOT pressure variation for most powders is more than you would see from a +- 0.1 gr variation in your 51.5 gr 270 load. For what it's worth I never bother using decimal increments for any loads over 50 gr - just whole numbers. Also, I never venture into the red zone pressure wise. All the flat-shooting hype I succumbed to when younger, pretty much lost its meaning when the laser rangefinder appeared on the scene.

+1..........:drinks:

[turbo1889]

This is why Benchrest shooters don't weigh charges. They use "clicks" on a culver type powder measure.

Being consistent with powder weight has been proven to have zero effect on accuracy. Powder VOLUME is much more important.

Weight is specified in loading manuals as it is easy for reloaders to understand and interpret. But volume will get you accuracy. . . .

EXCELLENT POST !!!

Yes, volume can mean more then weight IF you have a consistent way to measure volume which is partially dependent upon the physical characteristics of the powder itself and highly dependent on your volumetric measuring equipment and your technique.

So far the most consistent volumetric measurement system I have been able to come up with is a highly modified Lee Pro Disk Measure that has been equipped with an ultrasonic vibration generator and a rail slide system that allows for a zero tolerance slip fit between the hopper and the disks with the weight of the hopper keeping it tight on top of the disk stack rather then using the side spacers which allow some slack and leakage as originally designed and provides the ability to stack as many layers as I desire and isn’t limited to just a double stack although doing more then a quad stack becomes problematic but a single to a quad stack line-up will cover almost all cartridges in existence.

Ball powders where the balls are larger size and aren’t too fine and fine grain and/or short cut extruded powder seem to meter the very best in my custom modified measure. There is sort of a “sweet spot” in powder grain size and geometry right in there where the larger ball sizes and smaller grain and/or short cut extruded powders are in the powder grain size and geometry spectrum. There are of course some powders that don’t measure volumetrically worth a darn due to their grain geometry and size and need to be weighed on a scale to get consistent loads, Alliant STEEL is one of them.

One of the best examples I know of where volumetric measurement can be easily shown to be far superior to weighed charges is the small pistol cartridges. By small I do not mean 9mm. I mean 32-ACP, 25-ACP, 25-NAA, 380-ACP, 32-NAA, etc. Using a powder that meters well volumetrically such as the Accurate ball powders (#2, #5, etc.) and precision volumetric measuring tools all the way down to just the simple, basic, lowly, Lee powder dippers you can produce loads with better accuracy and tighter velocity strings over the chrony then you can with weighed charges measured to the 0.05 grains. I’ve done it and the numbers spit out by the chrony and the target boards printed don’t lie.

That said, I still generally recommend to the masses that they weight their charges for best results when loading shotgun slugs (a topic I discuss quite often with all sorts of people all over the web). Why? because of all the potential volumetric charge measuring tools the shotgun loading machine bushing assemblies are among the most crude and the most inconsistent of all short of possibly a tea spoon (even Lee dippers with good technique are better) and most shotgun powders have a grain geometry and size that does not meter well. Truth be told though, using a quality consistent volumetric measure like a precision rifle loader would use with a well metering powder like HS-6 would be as good or better but making the distinction and explaining that is a PITA at best.

[Recluse]

Since this discussion involves scales and weight variations, with a slew of reasons why discrepancies can easily exist, it has gotten the attention of my wife. . .

:coffee:

[Hurricane]

.1 difference in weight of powder has no meaning to me. I never push the maximum load data. It should have no meaning to you also unless you are overloading your ammo.

[btroj]

Since this discussion involves scales and weight variations, with a slew of reasons why discrepancies can easily exist, it has gotten the attention of my wife. . .

:coffee:

WOW!

You are either the bravest person I know or your wife doesn't know ow to access this forum.

[uscra112]

Wow! I never considered gravity variations, but it sounds plausible. I have read here and other sites that a 2% variation of powder isn't noticable as far as pressure and accuracy are concerned...

Gravity variation is all but impossible to measure without instruments a great deal more precise than our scales. That whole idea is beyond far-fetched.

[uscra112]

And I wonder at the validity of the argument that benchresters use volumetric measures. Is it perhaps just because they load at the range, and using a scale under "range conditions" is so difficult? I've tried, and what I had to do to get the scale to behave was inconvenient, to say the least.

Like the idea of using an electric vibrator. I may just appropriate that for my plain old RCBS drum measure. Maybe use the vibrator motor from an old pager or cell-phone. Consistent manipulation of the handle is hard to do. I weigh every charge anyway, and see the variation.

This is coming from a guy who just spent 15 years in process control metrology for GM/Ford/Chrysler. We always felt that anything you could control to tight tolerance (without excessive cost), you should control to tight tolerance. Charge weight is easy to do, so do it.

[Sonnypie]

And then the humidity changes, and it all goes out the window..... :(

Consistency matters.
Weight, or volume.
If there isn't consistency, in all elements, it's going to be just so much burnt powder.

Do the best you can humanly possibly do.
And avoid shooting where flies fart... ;-)

[miestro_jerry]

I keep "check weights" handy and check my scales regularly. I check my powder charges a lot also.

With electronic scales it is best to turn them on, do what ever reset and wait a half hour, check the scales again then start loading. Many of the electronic scales need to "warm" up to even them out.

Jerry

[turbo1889]

.1 difference in weight of powder has no meaning to me. I never push the maximum load data. It should have no meaning to you also unless you are overloading your ammo.

Or unless you are loading small pistol cartridges (again when I say small I mean small not medium/small like the 9mm). A maximum charge for the 25-ACP with one popular powder is 1.3 grains with a start charge of 1.0 grains. 32-ACP, 32-S&W, 32-Colt, and 25-NAA are a little better with the charges usually being at least two or three whole grains and the 380-ACP, 32-S&W Long, and 32-NAA are a little better still but you are still dealing with very small charges where 0.1 grains can be as great or greater a percentage of the total charge then 1.0 grains in many larger cartridges that use significantly more powder.

Long story short, if you load for pocket pistol cartridges and are measuring your charges by weight +/- 0.1 grains is significant and having a scale that is more precise then that like one that reads to 0.05 grains is very helpful. As I explained earlier though, with such cartridges your best bet for consistency is not a scale but rather a quality volumetric measure with a powder that is highly suited to volumetric measuring.


Gravity variation is all but impossible to measure without instruments a great deal more precise than our scales. That whole idea is beyond far-fetched.

With a balance beam type mass weight scale it has no meaning since any change will effect both sides of the balance beam. A balance beam scale will be accurate with no changes if you were to use it on the surface of the moon. Digital scales that use electronic strain gage pressure pads, however, are susceptible to variations in the gravity field since they don’t truly measure mass but rather measure the downward force that gravity places on the scale pan and use a calculator algorithm to convert this force to the displayed mass. What that conversion factor is set too does effect the results if the exact local gravity field doesn’t exactly match the conversion factor programmed into the electronics.

For example if an electronic reloading scale that measures to the 0.1 grains was programmed with a constant that would make it perfectly accurate in a local gravity field of 9.810 m/s^2 (sea level in an area with dense bed rock) and the location where it was being used instead had a 9.801 m/s^2 (higher elevation location like Denver) and I were to take that reloading scale and weigh out a powder charge of 110.0 grains the true actual weight of that charge would actually be 110.1 grains. Yes, I realize that there isn’t a whole lot of difference there as a percentage of the charge weight. But you also need to realize that there is rounding built into the calculation algorithm of the scale so you would only really need a charge weight of about 55 grains for there to be enough error in the internal calculation algorithm due to an incorrect gravity constant to push it over the edge and get the displayed value to be off by 0.1 grains due to the gravity constant alone being off combined with rounding error without any other error factors at all being introduced and assuming that the conversion factor programmed into the scales calculation algorithm is precise enough to not be outside the narrow range of “correct” potential terrestrial gravitational field values. The combined error between two different scales operated side by side can be even greater if we realize that very few of them even have an advanced and precise enough calculation algorithm to even hold the conversion factor tolerances tight enough to stay within the narrow range of normal variance much less adjust for local variance. I’m not suggesting that the local gravitational field variance makes a huge difference but I am trying to explain that an electronic scale doesn’t measure mass it measures the downward force that is the product of the mass of the powder charge being weighed and the gravitational force and that a conversion factor must be programmed into the scales electronics telling it how to convert the force it reads to mass units and the slightest variance in that conversion factor will make two different electronic scales results diverge from each other slightly as more mass is added or removed. Two electronic scales might agree with each other that 32.0 grains is indeed 32.0 grains on both scales. But drop that down to 10.0 grains and the second scale says it is 9.9 grains and then when the charge is increased to 45.0 grains the second scale says it is 45.1 grains. The second scale has a slightly higher conversion factor programmed into it then the first scale which makes lighter weights show up as slightly lighter then they actually are and heavier weights show up as slightly heavier then they actually are if you assume the first scale is perfectly accurate, or it could be the other way around, or most likely of all the truth is actually somewhere in-between and both scales are a little off in the conversion factors that are programmed into them with one slightly off to one side of the tolerance spectrum and the other off to the other side.

[KYCaster]

So you are actually shooting 75.1 gr instead of 75. Does it matter? I don't care as long as 75 gr is always 75.1. I want to know that the same object always comes up the same weight.

This is an instance where precision is more important the accuracy.


This is what's important.

It wouldn't matter if your scale was .3 or .6 off as long as you worked your load up properly. What matters is that you can repeat that load.




YES! What they said!

Repeatability is much more important than absolute value. As long as your scale shows the same reading for your check weight, you have nothing to worry about, regardless of what your friend's scale says. Just continue to use your scale and not his.

Jerry

[edward hogan]

About 20yrs ago I bought an RCBS deluxe weight check set.

I always adjust scale to zero on a value as close as feasible when loading powder, or setting up a measure for a given weight. Check the measure about every 10 or 20 rds, or adjust the measure to be light and use a dripper to finalize the charge.

Might be slower or perhaps considered tedious to break-out the little weight kit, but to be sure of my results I take the time.