Test of a self tuned 10-10

[BoydAllen]

I have a RCBS 10-10 that I tuned up some time ago. I also have a web cam that allows me to view the scale's beam pointer and scale on my computer's screen, greatly magnified, with no parallax error(because the camera does not move from reading to reading).

This morning I decided to do a short test to see how accurately I can trickle H4350 powder, using this setup, and weighing the results with a Bald Eagle electronic scale.

Along the way I learned a thing or two. The first was that it is easy to have a grain or two of powder fall onto the pan holder, while the pan is off of the scale. To prevent this, I pivoted my RCBS trickler (with tube extension in place) so that it could not spill onto the pan holder, before removing the pan from the scale, pivoting it back when the pan had been returned.

The other thing that I learned is that it is easier to use edges of marks as references, instead of centering. I lined up the top edges of the pointer line, with the top edge of the scale zero line.

Using a small sample of weighings (10), taking all of the time that was required to line things up, which involved dumping some powder and starting over a few times, I was able to produce an extreme spread of weights of .06 grains, which amounts to +-.03 gr. After that I weighed 10 pieces of the powder and found that the total was .30 grains, .03 gr. per piece

The bottom line is that with great care, and the use of a webcam, I was able to weigh to plus or minus one particle of H4350.

Talking with a gunsmith that is extremely involved in 1,000 yd. shooting, I was told that ESs in the range of 5-15 (for the Dashers that they commonly work with) is good to go, at a range that frequently has very good conditions.

If we look in the Berger manual we will see that for a .284 (picked because successful F UNL shooters have used H4350 for that caliber) with a 180 gr. bullet, and a 24" barrel, taking the highest and lowest loads and their respective velocities, we can calculate that one particle of powder (.03 gr.) will make a difference in velocity of 1.6 FPS, which means that my ES of weights would contribute 3.2 FPS to the ES of loaded ammo.

The question that this test cannot answer is what percentage of bullet velocity ES is attributable to variation in charge weight alone.

 

[sfldiver]

The other thing that I learned is that it is easier to use edges of marks as references, instead of centering. I lined up the top edges of the pointer line, with the top edge of the scale zero line.

That's a great tip, hadn't thought or that - Even enlarged via my computer/webcam, the edge of the line certainly would be easier to gauge. Thanks! Personally, I bought myself a Lyman Shooters Weight Check Set (https://www.midwayusa.com/product/212586/lyman-shooters-weight-check-set) that comes in grains. With that, I'm able to start off with a known weight, and really check the accuracy and repeatability of my scales. With my M-5 scale, tuned by Scott Parker (SPARKER) of course, I'm able to hit the center of the line dead-on consistently.

 

[johara1]

I have a RCBS 10-10 that I tuned up some time ago. I also have a web cam that allows me to view the scale's beam pointer and scale on my computer's screen, greatly magnified, with no parallax error(because the camera does not move from reading to reading).

This morning I decided to do a short test to see how accurately I can trickle H4350 powder, using this setup, and weighing the results with a Bald Eagle electronic scale.

Along the way I learned a thing or two. The first was that it is easy to have a grain or two of powder fall onto the pan holder, while the pan is off of the scale. To prevent this, I pivoted my RCBS trickler (with tube extension in place) so that it could not spill onto the pan holder, before removing the pan from the scale, pivoting it back when the pan had been returned.

The other thing that I learned is that it is easier to use edges of marks as references, instead of centering. I lined up the top edges of the pointer line, with the top edge of the scale zero line.

Using a small sample of weighings (10), taking all of the time that was required to line things up, which involved dumping some powder and starting over a few times, I was able to produce an extreme spread of weights of .06 grains, which amounts to +-.03 gr. After that I weighed 10 pieces of the powder and found that the total was .30 grains, .03 gr. per piece

The bottom line is that with great care, and the use of a webcam, I was able to weigh to plus or minus one particle of H4350.

Talking with a gunsmith that is extremely involved in 1,000 yd. shooting, I was told that ESs in the range of 5-15 (for the Dashers that they commonly work with) is good to go, at a range that frequently has very good conditions.

If we look in the Berger manual we will see that for a .284 (picked because successful F UNL shooters have used H4350 for that caliber) with a 180 gr. bullet, and a 24" barrel, taking the highest and lowest loads and their respective velocities, we can calculate that one particle of powder (.03 gr.) will make a difference in velocity of 1.6 FPS, which means that my ES of weights would contribute 3.2 FPS to the ES of loaded ammo.

The question that this test cannot answer is what percentage of bullet velocity ES is attributable to variation in charge weight alone.

I think 0 to 9 are the ES you are looking for......... jim

 

[BoydAllen]

On the ES, check your PMs.

 

[BoydAllen]

Jim,
How much of total ES would you credit to powder weight variation?
Boyd

 

[Ned Ludd]

The question that this test cannot answer is what percentage of bullet velocity ES is attributable to variation in charge weight alone.

Very nice write-up, Boyd. In terms of the last question, IMO it doesn't really matter what percentage of velocity variance is directly attributable to charge weight variance. Whatever the value is, it's not zero. So the idea is to weigh powder with enough accuracy/precision that the maximum theoretical value is sufficiently small that its effect on velocity can effectively be ignored. I typically weigh powder to +/- 1/2 kernel on a high-end analytical balance, which translates to under 1 fps velocity variance that is attributable to charge weight variance. The method I use to weigh powder would take me a similar amount of time, regardless of whether I chose to use a limit of 1/2 kernel, one kernel, or even 0.1 gr. Therefore, this approach doesn't require anything extra other than the analytical balance, which I am fortunate enough to have. It can certainly be argued that weighing powder to +/- 1/2 kernel is grossly excessive for my needs (F-Class). However, because it doesn't take much (if any) extra time for me, I know that charge weight variance is one thing that I never have to even consider if I see ES/SD values I don't like. In that event, eliminating one potential causative variable makes the correction process that much simpler. It's all about peace of mind for me .

 

[johara1]

Jim,
How much of total ES would you credit to powder weight variation?
Boyd

I don't really know if you could put a finger the amount. I can tell in a good barrel you can see a half a tenth. Saying that you better have very uniform neck tension.... i have as low as ES. 1 SD was 0........ and it would repeat in 5 or less.... jim

 

[BoydAllen]

I did this test mostly for those who are not ready to spring for a magnetic force restoration scale and would like to see what can be accomplished in the way of improving ES of charge weights. Of course the more expensive equipment is capable of doing more. I am especially excited to read of the new powered trickler that was designed to interface with a MFR scale. IMO, that is really trick. With a tuned balance scale, a webcam, and strict attention to getting your scale really at the same place for every charge you can measure powder to a very high degree of uniformity, certainly good enough to see whether that variable is is holding you back. If it turns out that it was, then you have to decide how much you want to spend to make it easier, and faster.

 

[Fast14riot]

I did a basic home tune up of a Lee Safety Powder Scale and am able to resolve repeatedly 2 kernels of 8208 without having refined either pointer, when viewed on a monitor. If I do add needles to the beam and body for alignment, then it's possible to resolve finer increments, but I wouldn't really trust this scale for anything finer than that. I also replaced the dampeners to increase hysteresis, which speeds up my weighing of charges rather than waiting for the feedback loop to close (return to zero).

 

[1066]

I did a basic home tune up of a Lee Safety Powder Scale and am able to resolve repeatedly 2 kernels of 8208 without having refined either pointer, when viewed on a monitor. If I do add needles to the beam and body for alignment, then it's possible to resolve finer increments, but I wouldn't really trust this scale for anything finer than that. I also replaced the dampeners to increase hysteresis, which speeds up my weighing of charges rather than waiting for the feedback loop to close (return to zero).

There are some excellent design features in the Lee scale. It's just a pity it was made so physically small and on such a tight budget.
Lee have continued to update their powder measures but the scale has remained the same for 30 years.
Come on Lee - introduce a scale at twice the size and twice the price, the market's ripe.

 

[hoz53]

I have a RCBS 10-10 that I tuned up some time ago. I also have a web cam that allows me to view the scale's beam pointer and scale on my computer's screen, greatly magnified, with no parallax error(because the camera does not move from reading to reading).

This morning I decided to do a short test to see how accurately I can trickle H4350 powder, using this setup, and weighing the results with a Bald Eagle electronic scale.

Along the way I learned a thing or two. The first was that it is easy to have a grain or two of powder fall onto the pan holder, while the pan is off of the scale. To prevent this, I pivoted my RCBS trickler (with tube extension in place) so that it could not spill onto the pan holder, before removing the pan from the scale, pivoting it back when the pan had been returned.

The other thing that I learned is that it is easier to use edges of marks as references, instead of centering. I lined up the top edges of the pointer line, with the top edge of the scale zero line.

Using a small sample of weighings (10), taking all of the time that was required to line things up, which involved dumping some powder and starting over a few times, I was able to produce an extreme spread of weights of .06 grains, which amounts to +-.03 gr. After that I weighed 10 pieces of the powder and found that the total was .30 grains, .03 gr. per piece

The bottom line is that with great care, and the use of a webcam, I was able to weigh to plus or minus one particle of H4350.

Talking with a gunsmith that is extremely involved in 1,000 yd. shooting, I was told that ESs in the range of 5-15 (for the Dashers that they commonly work with) is good to go, at a range that frequently has very good conditions.

If we look in the Berger manual we will see that for a .284 (picked because successful F UNL shooters have used H4350 for that caliber) with a 180 gr. bullet, and a 24" barrel, taking the highest and lowest loads and their respective velocities, we can calculate that one particle of powder (.03 gr.) will make a difference in velocity of 1.6 FPS, which means that my ES of weights would contribute 3.2 FPS to the ES of loaded ammo.

The question that this test cannot answer is what percentage of bullet velocity ES is attributable to variation in charge weight alone.

Thanks Boyd for providing this info. It's good to see you can get single kernel repeatability with your 10-10 scale. So I know I will be able to get that with mine if it is tuned well enough. I had thought of buying an MFR scale however for what I do now single kernal (or .03gr) accuracy is good enough. I do have a bald eagle electronic though and I will work with it some more.