problems with a precise electronic scale

[wildcat westerner]

Hello,
For years I shot long range benchrest and since I set two different Worlds records and thought I knew a thing or two about reloading. One thing that bugged me constantly was trying to get more velocity uniformity from shot to shot. I have a ridculously expensive scale which is supposed to weight to .001 and noted I could never get the consistency I wanted despite perfectly consistent case volumes, weighing primers etc.
Now I am retired to northern New Mexico, have access to long rifle ranges etc. Recently I noted a reference to a capacitor that is placed on the electronic line that creates consistent electricity to the scale. Since I am living in a rural area, this capacitor seems sensible to me. I was informed that when you use an oscilloscope, you can read a much more uniform amount of electricity when checking a capacitor equipped electrical line.
I hope there is somebody out there who understands the electriclal end of this puzzle and might be able to tell me exactly what capacitor, lines and fittings I will need so I can finally, after many years, start getting my chronograph reading, and target beyond 800 yards to be much more uniform. Thanks Gene

 

[Barrelnut]

Been ages since I messed with this stuff, but I think the capacitor is acting as a voltage regulator by absorbing some of the power when the voltage is high and giving some power back out as the voltage lowers. This is filtering out the spikes and general noise.

I think you just need a voltage regulator/power conditioner like this from Amazon.

http://www.amazon.com/dp/B00009RA60/?tag=lrhmag19-20

 

[Trickymissfit]

Hello,
For years I shot long range benchrest and since I set two different Worlds records and thought I knew a thing or two about reloading. One thing that bugged me constantly was trying to get more velocity uniformity from shot to shot. I have a ridculously expensive scale which is supposed to weight to .001 and noted I could never get the consistency I wanted despite perfectly consistent case volumes, weighing primers etc.
Now I am retired to northern New Mexico, have access to long rifle ranges etc. Recently I noted a reference to a capacitor that is placed on the electronic line that creates consistent electricity to the scale. Since I am living in a rural area, this capacitor seems sensible to me. I was informed that when you use an oscilloscope, you can read a much more uniform amount of electricity when checking a capacitor equipped electrical line.
I hope there is somebody out there who understands the electriclal end of this puzzle and might be able to tell me exactly what capacitor, lines and fittings I will need so I can finally, after many years, start getting my chronograph reading, and target beyond 800 yards to be much more uniform. Thanks Gene

first of all I'm not an electrical engineer, and actually have a phobia with electricity! Yet I've spent weeks in seminars and schools concerning electrical engineering. I'm OK with logic, but unlike 95% I am barely up to snuff with magnetics. Here's what I know, and maybe someone will re-educate me.

Believe it or not electricity for the most part works a lot like hydraulics and pneumatics. With hydraulics we often use an energy storage device called an accumulator. The capacitor is similar in function. But the accumulator will also absorb shocks and pulsations in the circuit to a certain extent. Still nothing major. We then think of back pressure in one form or another. In an electrical circuit, this is called a choke coil. With hydraulics will simply add a one PSI check valve or another device to kind of create a little bit of back pressure. This is real common with cylinders and servo systems. This is pretty much all a power conditioner does in an electrical circuit, but many take it a step further

If you look on Ebay, you can buy them for any where from forty dollars to four thousand dollars. I often use one that I bought for thirty bucks, and it works well. Still it will not compensate for anything non-electrical. These same things also effect a beam scale so that's not worth bringing up.

what we need is a good 24 volt DC scale with a good 24 volt DC power source (most use el cheapo junk.) Direct current is much more stable than typical 120 volt house current.
gary

 

[Dr. Vette]

Some also find that fluorescent lights will cause drift in a scale.

One of mine will drift if my reloading computer is on at all. I have to shut it down completely (not just sleep mode) in order to have the scale stabilize even though I added an electrical noise filter and magnets to the power lines. The other scale doesn't seem to be bothered by anything, and as long as it has been on for an hour or so prior to use it works extremely well.

 

[Bart B]

Yes, electronic digital scales are sensitive to fluctuating voltages and currents from the power source that are not totally filtered out before they get to the stuff calculating the weight reading.

Go back to a beam scale and weigh charges to a 1/10th grain spread. There's a greater spread in muzzle velocity across a lot of the best primers made correctly fired than what 1/20th grain difference in powder charge will show.

Ensure your firing pin sticks out past the bolt face at least .060" for large rifle primers and the firing pin spring's up to factory specs or even 10% over.

When you weigh primers, how do you separate the priming pellet's weight from that of the cup, anvil and seal? Do you take them apart to weigh the pellet then put 'em back together? Or are all cups, anvils and seals the exact same weight?

 

[Trickymissfit]

Some also find that fluorescent lights will cause drift in a scale.

One of mine will drift if my reloading computer is on at all. I have to shut it down completely (not just sleep mode) in order to have the scale stabilize even though I added an electrical noise filter and magnets to the power lines. The other scale doesn't seem to be bothered by anything, and as long as it has been on for an hour or so prior to use it works extremely well.

the way to fix this problem is super simple, but nobody does it. Build the scale to run at 50Hz instead of the typical 60Hz. Your whole house generates a 60Hz field all thru it. This is a trick high end audio uses to make systems quieter and more stable. You convert to DC and then convert that to 50Hz, and all the issues are gone. By the way that 60Hz generates a vibration, and all scales are effected to a certain extent.
gary

 

[Trickymissfit]

Yes, electronic digital scales are sensitive to fluctuating voltages and currents from the power source that are not totally filtered out before they get to the stuff calculating the weight reading.

Go back to a beam scale and weigh charges to a 1/10th grain spread. There's a greater spread in muzzle velocity across a lot of the best primers made correctly fired than what 1/20th grain difference in powder charge will show.

Ensure your firing pin sticks out past the bolt face at least .060" for large rifle primers and the firing pin spring's up to factory specs or even 10% over.

When you weigh primers, how do you separate the priming pellet's weight from that of the cup, anvil and seal? Do you take them apart to weigh the pellet then put 'em back together? Or are all cups, anvils and seals the exact same weight?

Bart,

I'm not questioning your wisdom in anyway, but I can't see weighing primers helping all that much. I like to use almost nothing but Federal match primers out of the same lot #. Never tried weighing a hundred of them to see what kind of a variance there would be
gary

 

[wildcat westerner]

Hello to all who have entered their thoughts on this challenge. I have read everyone's inputs here and spoken with several poeple in the electrical field. I do have flourescent lights in my reloading room.

I have a pretty powerful 12v starting device. I plan to use it, connect a true sine inverter to this unit and run my power cord to the scale from the inverter. I will ,using my knowledge about precise reloading AND my chronograph tell me whether this way of using my scale is more accurate than it was when plugged into the house 120V system.

I will report to you my results.

Thanks to everyone for their input which I value.

Gene S.

 

[Bart B]

Gary, my comments on weighing primers was intended to point out the futility of getting any meaningful data.

According to this patent on Federal Primers:

Patent US5831208 - Lead-free centerfire primer with DDNP and barium nitrate oxidizer - Google Patents

the weight tolerance for their components appear much bigger than that of a powder charge.

There's other interesting links in the above for primers from other companies.

 

[Trickymissfit]

Gary, my comments on weighing primers was intended to point out the futility of getting any meaningful data.

According to this patent on Federal Primers:

Patent US5831208 - Lead-free centerfire primer with DDNP and barium nitrate oxidizer - Google Patents

the weight tolerance for their components appear much bigger than that of a powder charge.

There's other interesting links in the above for primers from other companies.

most interesting Bart!

Some time back a very well known bench rest shooter told me that for him the two most critical things in building match winning ammunition was neck tension, and case volume. He found a few tenths difference in neck tension would often reduce his spread dramatically. During that same period I was weighing cases like nobody's business. He said it was a waste of time. He said that case volume was much more important. Yet there was a lot more to this. He said all brass must be from the same lot, and have exactly the same dimensions. He also said the rounds he shot in matches had the same amount of shots thru them. Then there's the bullet issue. A custom bench rest bullet is still not perfect. That bench rest shooter had a friend build bullets for him. I honed and ground stuff for him all the time, and he told me once that 3/4 of the stuff ended up in the trash as the experiment didn't pan out. That old man told me once that the J4 jackets he used could have been made a lot better. I had a plan, but we never got down to doing it. Remember a .0001" error in the c/g of a bullet generates .093" error at 100 yards, and doesn't include differences in bullet weight and shape errors.
gary

 

[Bart B]

Gary, the most interesting thing about all the infatuation with tiny groups at short ranges is the record aggregates for groups shooting at 100 yards. Records for several 5- or 10-shot groups about .200"; the average size of all groups. Biggest group fired is somewhere in the .3XX range and smallest is typically some size sub .100". So the rifles and ammo that shoot them keep all fired record groups at 100 yards somewhere under .3XX inch.

Compare that to Sierra Bullets newest accuracy specs for all their Match King bullets; all 10-shot test groups at 200 yards must be under 1/2 MOA or 1 inch. That includes their 33 caliber 300-grain bullets for .338 Mags as well as 22 caliber ones for the 22 PPC. Yes, the smaller caliber ones typically shoot smaller test groups. They meter all test round charge weights; none are weighed.

Hornady's accuracy specs for all their match bullets in their 200 yard test range is .950"

I've no idea what Berger's specs are.

 

[rcoody]

Gary, the most interesting thing about all the infatuation with tiny groups at short ranges is the record aggregates for groups shooting at 100 yards. Records for several 5- or 10-shot groups about .200"; the average size of all groups. Biggest group fired is somewhere in the .3XX range and smallest is typically some size sub .100". So the rifles and ammo that shoot them keep all fired record groups at 100 yards somewhere under .3XX inch.

Compare that to Sierra Bullets newest accuracy specs for all their Match King bullets; all 10-shot test groups at 200 yards must be under 1/2 MOA or 1 inch. That includes their 33 caliber 300-grain bullets for .338 Mags as well as 22 caliber ones for the 22 PPC. Yes, the smaller caliber ones typically shoot smaller test groups. They meter all test round charge weights; none are weighed.

Hornady's accuracy specs for all their match bullets in their 200 yard test range is .950"

I've no idea what Berger's specs are.

Spinning bullets!

http://bulletdoctor.com/

 

[Lefty7mmstw]

While I think it is a good thing to make your cartridge as perfect as you can make it, exact powder charge, perfectly concentric case volume, etc.. it is next to impossible to get exactly uniform velocities out of the cartridge alone.

The barrel has a good amount of say in how fast and uniform your ammunition is too. As the barrel heats it expands a bit... It expands both outward and inward. I have noticed it (without looking for it) using strain gauges years ago on my 7stw. I could actually get the barrel hot enough to get another 7Kpsi out of a normal i7828/ 140 sierra load while still being able to touch the barrel without discomfort. Let the barrel cool and the pressures return to normal. Your fouling (as it accumulates) has some say in your velocity also...

 

[Bart B]

it is next to impossible to get exactly uniform velocities out of the cartridge alone.

Take the barreled action out of the stock then clamp it in a fixed mount that doesn't move when the loaded round's fired. Muzzle velocity average will be faster than if you hand-hold the rifle or shoot it in free recoil. But the spread will be the smallest; sometimes 1/4th to 1/5th that of what it is hand holding the rifle.

Every wonder why several people shooting the same rifle and ammo get different muzzle velocity averages and spreads thereof as they hold the rifle to their shoulder? Averages often have a 50 to 100 fps range.