What class of weight to use?

[Raythemanroe]

I'm gonna need to get a 300g weight to zero my scale, what class of weight do you guys recommend?




Ray

 

[jlow]

To figure that out, know how far deviation (flaw) you are willing to accept in terms of mg from the stated weight and then look up the class from the table in this website.

http://balances.com/sartorius/calibration+weights.html

 

[amlevin]

Are you trying to send a bullet 1K yards downrange or to the moon.

Some people think that using a bullet for a scale "standard" is enough for the 1K needs.

 

[Raythemanroe]

Are you trying to send a bullet 1K yards downrange or to the moon.

Some people think that using a bullet for a scale "standard" is enough for the 1K needs.

I would prefer to just buy a $10 weight and think I'm okay with a a milligram tolerance. I'll Recalibrate using the directions I think, after reading up a bit..



Ray

 

[Keith Glasscock]

Here is my take:

You are going to do load development right? Does it matter any if the number associated with the optimal load is 45.22 or 45.32? Will the most accurate charge be less accurate?

We all know that the answer to the above is no. The goal therefore has to be consistency. To do that, use the same calibration weight and take good care of it so it doesn't change (nicks and gouges are not good).

So what class to use? Use the least expensive one and use only that one.

Just my opinion...
Keith

 

[jlow]

Are you trying to send a bullet 1K yards downrange or to the moon.

Some people think that using a bullet for a scale "standard" is enough for the 1K needs.

I would prefer to just buy a $10 weight and think I'm okay with a a milligram tolerance. I'll Recalibrate using the directions I think, after reading up a bit..



Ray

I think that is a reasonable assumption. One can go overboard buying this kind of stuff and as it is with reloading, we are mostly working on consistency (precision) and less on absolute accuracy when it comes to weighing power.

 

[Raythemanroe]

Busdriver (Keith), I think that is sound advice. My intended use it would be pointless and no more effective..


Ray

 

[rminut]

I agree but I might add that it helps to have a check weight near your usual charge weight because scale accuracy can differ at different points through it's range. Calibrating the scale at 300 grams doesn't really guarantee the same accuracy at 45 grains. That is why many have a bullet near the charge weight, as someone mentioned. The accuracy typically gets worse as you get farther from the calibration weight.

 

[kyreloader]

I bought a class 1, couldn't see saving money on a calibration weight after just spending that amount of money on a digital scale.

 

[amlevin]

I bought a class 1, couldn't see saving money on a calibration weight after just spending that amount of money on a digital scale.

The only time a Class 1 calibration weight will make a difference is if you are trying to make YOUR readings match someone else's readings. That's when the calibration weight needs to be accurate, meaning the same as someone else's cal weight.

With load workup you are developing your charge weights for your rifle, not using someone else's results you have to duplicate within a granule.

The issue isn't that the scale reads exactly, but that it repeatedly gives the SAME readings. That's going to be determined by the resolution of the scale itself. If you bought a digital scale from the local "Doper Supply Store" for $8.95 that was designed to be within a "leaf or two of pot", it has a resolution of +/- 2 grains. If you are using a common reloading scale +/- .1 grain is considered more in line. If you want to measure granules then a Gempro or Sartorius is in order. With them, check weights are often made with minute differences so you can see if the scale will actually detect the differences.

For the most part we all just use a weight that is close to the charge weight and then rely on the scale makers "resolution" for accuracy. I use the RCBS check weight sets to build a set of weights that mimics the charge weight I'm working with to the nearest "tenth or two". That's tells me if the scale is accurate enough for weight and I refuse to "count granules".

 

[jlow]

The only time a Class 1 calibration weight will make a difference is if you are trying to make YOUR readings match someone else's readings. That's when the calibration weight needs to be accurate, meaning the same as someone else's cal weight.

I would even say that example would not make a difference. If you are using a class 1 weight and you were off 0.75mg out of 300 grams, that is an off value that is so much less than other environmental factors one normally have to deal with such as variance in powder, different barrel/bullet/case/primer, different temperature, etc.

 

[Raythemanroe]

If your scale is calibrated with a good weight you could make your own check weights right? I actually found some class 1 three set weights on Ebay, Couple more left:

http://www.ebay.com/itm/121387020000?_trksid=p2060778.m2763.l2649&ssPageName=STRK%3AMEBIDX%3AIT


Ray

 

[normmatzen]

Right on!
I have an Ohaus TS200 which has accuracy, drift and linearity to 1 mg. That is about 0.013 grains. This accuracy lets me load to a granule of Varget or H4831sc.

I am primarily concerned with consistency of loads over time so my solution to The test mass problem was to get two masses equal to 1/2 the full scale calibration mass. Then, weigh these carefully with my balance and take the heaviest one and set it on a piece of 600 grid emery paper and sand a little.
Then clean with alcohol and dry it and again compare the two masses. When they both indicate the same weight on the balance. I am done. Now, I can calibrate with the two masses for full scale and linearity with one.
I may be off a bit, but my loading session to loading session is accurate to better than 1 mg. And, I keep these "standard" masses in a box away from dust and contaminants.
I also have a set of weights in the range of fractional grains to 20 grains so I can monitor a "load" of say, 33.5 gn and it always reads right on.

 

[jlow]

I see you clean your "standard" masses. You can do this but in the lab, we NEVER touch any of the calibration weights with our bare hands but use gloves when handling them. The reason is skin oil and salt can get on them and cause weight deviation and oxidation, something you never want to happen to your standards.

 

[amlevin]

I see you clean your "standard" masses. You can do this but in the lab, we NEVER touch any of the calibration weights with our bare hands but use gloves when handling them. The reason is skin oil and salt can get on them and cause weight deviation and oxidation, something you never want to happen to your standards.

I can see it now. Those who want to get the utmost accuracy will now start hand loading in "Clean Rooms" . No more flannel shirts and bib-overalls, but "moon suits" so it will be hard to tell if one is loading precision ammo or fighting Ebola 8) 8) 8)


Think I'll stick with my "Retro Approach" with my RCBS 5-0-5 and their check weights that have been handled more than some hollywood starlets ;D ;D

 

[M-61]

Repeatability for me is the goal. It is why it took me until last year to buy an electronic scale. (Chargemaster).
I felt the beam (Ohaus 304) was doing to REPEAT reliably. The actual weight was not the concern so to speak, rather will it show this number, with same weight , again and again. Flashing numerals on a screen did not instill the same level of confidence that the beam scale did. It took a while to 'trust' the digital scale. It is nice to have the EXACT same weight thrown but I'm not sure of the definition of EXACT in this application, meaning
plus one hundredth or minus one hundredth I don't feel is going to show on a target especially when all the other variables are factored in. Limiting the variables is important but as someone above said you don't want to be in a 'Moon Suit' to reload satisfactorily.

 

[jlow]

It's more like common sense. You pay good money and buy something that has a specific weight variance but they you go pick the thing up after eating burgers and gets your greasy salty paws on it to change its weight - dah.... :

Use your head!

 

[normmatzen]

jlow,

You have a good point. I neglected to mention that when I reload, or mess with my balance, I wear surgical gloves. It is just as bad to get body oil on bullets!

 

[normmatzen]

M-61
The whole idea is to treat your reloading with respect. Maybe the 1/2 granule I load to is not going to make a difference, or the bullets with 15% difference in seating force etc. etc. But "aim small, shoot small."
I went to better balances when I bought the little set of masses in sizes from 0.5gn or so to 20 gn. Then I could test my three old beam balances and was astonished in how much variation there was. Between balances and in just one of them!
I shoot primarily long range bench rest and there is no way to get as close to perfect loads without paying attention to EVERY parameter you can measure. And then, you better use an accurate tool to do the measuring!

 

[krprice84]

Keith summed this one up perfectly. The need for perfect weights is completely non-existent for loading, so long you use the same imperfect weights every time and don't let them get dirty or dusty etc.

If you think you are using 43.2 grains of powder but are really using even 43.5, but have arrived at that charge through proper development, then does it really matter what that charge really weighs? The only time it might matter is when using more than one scale or switching scales. Then you would either want perfection or you would want to slightly redevelop your load.

Even when verifying an electronic scale with a beam scale, I wouldn't worry about the weights matching but would want then to read the same for each scale every time. So if my gem pro says 43.2 but the rcbs beam says 43.4, so long as they say that every single time, who cares?

And even when going with other people's loads, first you shouldn't do that and should always start a bit lower than their load and work up, but second, even if you have an ultra class, 150 dollar traceable calibration weight, does the other guy? Maybe the numbers he gave you are from an old, damaged scale, or maybe he dropped his cal weight and damaged it, making it inaccurate. Who knows. Always work up the load somewhat, never trust someone else's numbers completely, and always strive for as much consistency as you feel you can do and not feel like you're a nut job (or, if you want to know your a nut job, then go that far - I do )