# How critical is measuring powder to .01 grains

I just got an FX120i and don't really know how I feel about it honestly. I verified quite a few charge weights that I had thrown from my .1 powder thrower. They were all within .03-.04gr.

So a .8% maximum deviation on a 60gr. charge and .5% maximum deviation on a 90gr. charge.

So for the 30 cal 90gr. charge, that has the potential for a 1" vertical deviation at 1000 yards based off 198" of drop and 2.75" deviation at 1500 yards based off 546" of drop.

I think I'll still weight my long range hunting loads to the .01 but wont waste my time on much other stuff.
Have you simply tried shooting a few ten shot groups at 1000yds to see how the two loads compare? I haven’t shot F-class since 2013, but when I did, the winners never had anywhere near just 1” of vertical. 2.5”+ would have been a really great load from a really great gun if I’m not mistaken.

If you can go shoot 2-3 ten shot groups loaded to .01 and 2-3 tens shot groups loaded with the FX120i and get statistically meaningful differences, then by all means, keep doing what you’re doing. If you can’t tell the difference though, why not use the FX120i?

Personally I think this whole premise is funny. Are all your case capacities within 1/100 of a grain? What about your bullet dimensions and weights.
If it makes you feel better, by all means, do it. It does not matter what I or anyone else thinks.
In engineering school we had a joke: What is the difference between a scientist and an engineer? And we had an example to demonstrate it.
In a square room the put a scientist and an engineer in on corner. On the diagonal corner the placed \$10,000. They told them the can move half the distance at each move. WHen they are close enough, the money is theirs, first man gets it.
Scientist pulled out a piece of paper, drea diagrams, wrote equations, pulled out his scientific calcluator, started puncnhing buttons, and then threw everything up in frustration say "I will never get there"
Meanwhile, the engineer, made two moves, then said, "I am close enough, money is mine"
We all have the freedom to choose!

Personally I think this whole premise is funny. Are all your case capacities within 1/100 of a grain? What about your bullet dimensions and weights.
If it makes you feel better, by all means, do it. It does not matter what I or anyone else thinks.
In engineering school we had a joke: What is the difference between a scientist and an engineer? And we had an example to demonstrate it.
In a square room the put a scientist and an engineer in on corner. On the diagonal corner the placed \$10,000. They told them the can move half the distance at each move. WHen they are close enough, the money is theirs, first man gets it.
Scientist pulled out a piece of paper, drea diagrams, wrote equations, pulled out his scientific calcluator, started puncnhing buttons, and then threw everything up in frustration say "I will never get there"
Meanwhile, the engineer, made two moves, then said, "I am close enough, money is mine"
We all have the freedom to choose!
Apparently spelling isnt stressed in engineering school? lol

TLC
Apparently spelling isnt stressed in engineering school? lol
Nope, not at all! What did you expect? American Universities. Neither was typing when I went to school. Just make sure calculations are accurate

I've been shooting a 6 BRA in 600 benchrest matches reloading Berger 105 hybrids with Varget. I was using a RCBS Chargemaster, and would see ES of around 20 and an SD right around 10. I started trickling with the RCBS and verifying and correcting with a Creedmoor Sports TRX 925, and all my ES and SD's fell with more than 1/2 coming in with ES around 10 and SD about 3.
Finally someone with actual use data supporting the idea. I like it.

Still, I assume you’re using less than 35gr of powder. My three hunting cartridges use 51-63gr, so depending on what cartridges and what range a person is shooting, I would estimate that measuring to .02gr lands somewhere between meaningless, and slightly useful.

Scanned quickly and didn’t see this video anywhere. Was fairly convincing for me.

BLUF: no it didn’t make a ton of difference.

Nope, not at all! What did you expect? American Universities. Neither was typing when I went to school. Just make sure calculations are accurate
The edjucation begins after gradyouation anyways. lol

TLC
The edjucation begins after gradyouation anyways. lol
for us not well educated, what is "edjucation"?

for us not well educated, what is "edjucation"?
I would imagine it is the same joke as “gradyouation”.

Scanned quickly and didn’t see this video anywhere. Was fairly convincing for me.

BLUF: no it didn’t make a ton of difference.

Thank you!

Calculating significance of his velocity variations gives a P-value of .405. For those of you not familiar with statistics, that means that it’s impossible to tell from the data if the two loading methods have different outcomes. Generally something is not considered statistically significant unless the P-value is below .05. This was not even close. It was not even close to close. This small data set suggests that there is NO DIFFERENCE between loading to +- .1gr and loading with the AutoTrickler V3. NO DIFFERENCE. He could repeat the test and if the chargemaster won, we should not be surprised. A larger data set would give better resolution, but with a P-value of .405, we would need a much larger data set.

None of this accounts for the fact that there is error in the dang chrono. We’re talking about weighing powder to a level precision that contains measurement error(the FX120i is not perfect to the level that it reads to and neither is the chargemaster), then we’re testing velocity to a precision that leaves measurement error from the chrono. Then we’re looking at tiny data sets and not considering probability and statistics.

Last edited:
weigh kernels of the powder you using. I use extruded powders.
My kernels are .02 or larger.
Better technique weigh 10 or 20 and take the average.

Well, since this has degraded into a comparison of automatic loaders and scales and the fact that I am both an engineer and scientist I think I will chime in on the subject.

First off, I have no experience with the Autotrickler V3. But I will accept it is a good device. That assessment is based on reviews and forum threads. I will comment on the Fx-120i. This scale is excellent. But it is also misunderstood in relation to accuracy. The manual for the 120i gives a linearity of +/- 0.002grams and a repeatability standard deviation of 0.001 gram and a minimum weighing capability of 0.001gram. None of these are an "accuracy" statement in the classical sense. The linearity is what is referred to as trueness in ISO standards and is commonly known as a bias error. It represents how far from the true value a weight may be indicated. The repeatability is a precision error meaning what variation may exist when the same weight is measure multiple times. The minimum weighing capability is the amount of weight required to increment the display. It can only resolve .001 grams. To convert these specifications to something akin to "accuracy" as nominally stated in specification requires analysis. First is the combination of the trueness and precision to give a 95% accuracy. This is calculated as the square root of the trueness^2 plus (2xrepeatability)^2. This is ~.0028grams. To this value the minimum weighing capacity of 0.001 grams must be added for a final accuracy of ~0.0038grams. This is equal to 0.058 grains. Call it .06 grains. But since we are not concerned with trueness error per se because we are only concerned with precision the 95% confidence level is 2x standard deviation of precision plus the minimum weighing capability which is 2x.001g+.001gram or .003 grams. This is .046 grains or about 0.05 grains. Bottom line, the classical accuracy of the Fx-120i is 0.06 grains.

The ChargeMaster 1500 quotes an accuracy of 0.1grain. When stated in such a manner this means that if a given weight is weighed a large number of times 95% of the measurements will fall within 0.1gr of the true value. This includes linearity (bias), precision and resolution accuracy. Since the display is 0.1 grain the effects of bias and repeatability are much less (less than 0.05 grains) and the electronics of the scale work on a more accurate level not affected by the scale resolution. I have personally verified the 1500 accuracy on multiple occasions.

Now the accuracy of the dispenser! When the ChargeMaster 1500 first came out there were too major complaints about its operation. One was that it was too slow and the other was it overthrew charges. To understand the issues it helps to understand the operation of the dispenser. It uses a single feed tube that runs at multiple speeds to dispense the charge. The speeds run from high to trickle. The dispenser slows its speed as it approaches certain load points. When in trickle mode the feed tube rotates a portion of a turn and stops to allow the scale to stabilize and then turns again until the target is met.

The problem of overthrow was minimized by the now famous straw modification that used a plastic straw to provide a smooth outlet of the dispensing tube to allow less material to drop per trickle rotation. It was later found that a bushing would also work. One of the more ingenious methods was to use the neck end of a 243 case (my method).

The speed issue was addressed by programming changes to speed up the loading. Unfortunately, doing so also increases the potential for overthrows. However, the same parameters can be used to optimize the trickling.

As it turns out, when the two methods (programming and bushing) are combined and optimized to the powder being thrown test have been published that show the 1500 is capable of throwing charges to the 0.05 grain level (verified by Fx-120i level scales).

This should not be taken to mean that the 1500 or other 0.1gr auto throwers will equal a V3 but it does mean that they are capable of 0.1 grain or better.

Mr. Lee , for me it is 1/10 of a grain for hunting bullets, and exact weight for target bullets. Example: The 115 Grn. Berger Flat Base Targets for my .308 . I have yellow Berger bullet boxes labeled 114.8 ;114.9 115.0 and 115.1. I use those for Bullseye Target shooting in my .308 Target rifle. This three-shot groupe measured .221 Center hole to center hole. from a factory stock Savage Rifle, untuned. unbeded. As per the rules of that "Score " match. The second photo is a three shot groupe that was a .162 from Center hole to Center hole. Last year I was 73 Years old and I could never achieve that degree of precision , from a rifle out of the box, without very careful handloading. It's amazing what you can do just being fussy!!! BUT as you can see they are not touching the dot INSIDE the Bulls eye, so I did not win anything. Maybe Ill take up Golf or something easy!!!!
I have take several rifles out of the box and put a lot of groups together in the 1/2" range, by using reload.
So your accuracy increased by using graded bullet weight? Interesting! I did that a great many years ago. Can't remember what took places. I know I like it, but didn't get out there and measured with calipers to see if there was a decrease in groups. Being a carpenter my tape measure was good enought for me at that time. Anywhere at a about 1/2" was good. It was outside of holes, not center of holes. Please let me know. Thanks.

Well, since this has degraded into a comparison of automatic loaders and scales and the fact that I am both an engineer and scientist I think I will chime in on the subject.

First off, I have no experience with the Autotrickler V3. But I will accept it is a good device. That assessment is based on reviews and forum threads. I will comment on the Fx-120i. This scale is excellent. But it is also misunderstood in relation to accuracy. The manual for the 120i gives a linearity of +/- 0.002grams and a repeatability standard deviation of 0.001 gram and a minimum weighing capability of 0.001gram. None of these are an "accuracy" statement in the classical sense. The linearity is what is referred to as trueness in ISO standards and is commonly known as a bias error. It represents how far from the true value a weight may be indicated. The repeatability is a precision error meaning what variation may exist when the same weight is measure multiple times. The minimum weighing capability is the amount of weight required to increment the display. It can only resolve .001 grams. To convert these specifications to something akin to "accuracy" as nominally stated in specification requires analysis. First is the combination of the trueness and precision to give a 95% accuracy. This is calculated as the square root of the trueness^2 plus (2xrepeatability)^2. This is ~.0028grams. To this value the minimum weighing capacity of 0.001 grams must be added for a final accuracy of ~0.0038grams. This is equal to 0.058 grains. Call it .06 grains. But since we are not concerned with trueness error per se because we are only concerned with precision the 95% confidence level is 2x standard deviation of precision plus the minimum weighing capability which is 2x.001g+.001gram or .003 grams. This is .046 grains or about 0.05 grains. Bottom line, the classical accuracy of the Fx-120i is 0.06 grains.

The ChargeMaster 1500 quotes an accuracy of 0.1grain. When stated in such a manner this means that if a given weight is weighed a large number of times 95% of the measurements will fall within 0.1gr of the true value. This includes linearity (bias), precision and resolution accuracy. Since the display is 0.1 grain the effects of bias and repeatability are much less (less than 0.05 grains) and the electronics of the scale work on a more accurate level not affected by the scale resolution. I have personally verified the 1500 accuracy on multiple occasions.

Now the accuracy of the dispenser! When the ChargeMaster 1500 first came out there were too major complaints about its operation. One was that it was too slow and the other was it overthrew charges. To understand the issues it helps to understand the operation of the dispenser. It uses a single feed tube that runs at multiple speeds to dispense the charge. The speeds run from high to trickle. The dispenser slows its speed as it approaches certain load points. When in trickle mode the feed tube rotates a portion of a turn and stops to allow the scale to stabilize and then turns again until the target is met.

The problem of overthrow was minimized by the now famous straw modification that used a plastic straw to provide a smooth outlet of the dispensing tube to allow less material to drop per trickle rotation. It was later found that a bushing would also work. One of the more ingenious methods was to use the neck end of a 243 case (my method).

The speed issue was addressed by programming changes to speed up the loading. Unfortunately, doing so also increases the potential for overthrows. However, the same parameters can be used to optimize the trickling.

As it turns out, when the two methods (programming and bushing) are combined and optimized to the powder being thrown test have been published that show the 1500 is capable of throwing charges to the 0.05 grain level (verified by Fx-120i level scales).

This should not be taken to mean that the 1500 or other 0.1gr auto throwers will equal a V3 but it does mean that they are capable of 0.1 grain or better.
All good info. Great info really. I don’t know if you were referring to me or not, and am by no means picking a beef with you. I’m just posting what’s below to clarify what I was getting at in my post about the video.