Are check weights accurate?

[Fire Guy]

I have been having a problem with my RCBS 5-10 scale so I acquired an RCBS M500 scale. I have a set of Lyman check weighs from .5 to 210.5gr. Using my check weights I'm finding the M500 to have a discrepancy of up to .4 grains at 200 grains. (Weighing 200.4 grains). I'm not sure if the problem is the scale or the weights. I have no idea where I can go to have the check weights calibrated or certified. Any suggestions?

[M1NM]

I'd vote the weights are more accurate than the scale. Here is how to set up the beam scale. https://www.youtube.com/watch?v=GSsdpXMhQfI

[JackEllis]

I calibrate my beam scale several times during a reloading session using a set of check weights. Within reason I'm not as concerned about the absolute value of the charge as I am about making sure the charges are as consistent as possible from one cartridge to the next.

[NikNak]

No issue, just load & shoot!

I have been having a problem with my RCBS 5-10 scale so I acquired an RCBS M500 scale. I have a set of Lyman check weighs from .5 to 210.5gr. Using my check weights I'm finding the M500 to have a discrepancy of up to .4 grains at 200 grains. (Weighing 200.4 grains). I'm not sure if the problem is the scale or the weights. I have no idea where I can go to have the check weights calibrated or certified. Any suggestions?

[JackEllis]

You must also have "the knack".

[kcstott]

1. it don't matter what you use for a check weight as long as you use the same check weight each and every time.

2. Check weights come in a variety of specifications from an 7 in ASTM specs to a E1 spec in OIML RIII 2004.

The real issue is people get caught up in the numbers. THE NUMBERS MEANS NOTHING. read that again if you need to but it's true. For what we are trying to do in reloading is just have as close to the same powder charge thrown as the last time. Hence why the check weights you get with your scale are not the highest of precision to an absolute value. (read that as a lower specification) Again it doesn't matter so long as the weight registers the same deflection on the scale each and every time. That is repeatability

More critical to the operation is not the accuracy of the scale but the repeatability of the scale. Will it read xx.x 99 out of 100 time the check weight was placed on the pan? thats the key. Does your scale read 220.4 grains 9 out of 10 times or 24 out of 25 time placed on the pan? If it does don't worry about the number it means nothing. Repeatability is key.

[rg1]

My Lyman check weight set weighed on a Gempro 250 shows all the check weights to be perfect except one. One weight shows a .02 above which is really nothing to be concerned about. I was surprised to see how accurate the Lyman check weights were and the Gempro 250 capable of measuring them. On another electronic scale the one weight showed 20.0 rather than 20.02 grains. I would say it's your scale but at 200 grains it's plenty accurate showing such a small deviation.

[Fire Guy]

Thanks for all the help. I realize that repeatability is the key to reloading I'm just a little compulsive. Ok maybe a lot compulsive, but I figure the company claims an accuracy rating of .1 over the range of the scale. The problem for me is discrepancy grows exponentially as the weight increases. About .1gn at 50 to .4 at 200. Like I said I realize in the grand scheme of things it's probably a moo point, just annoying. ( Moo point, it's a cows opinion, it doesn't mean anything. It's moo. Joey Tribiani.) Thanks again.

[Odd_Ball]

Mooooo!!!

[hambam105]

Check weights? How serious of an approach to reloading do you want to take?

[J-cat]

1. it don't matter what you use for a check weight as long as you use the same check weight each and every time.

2. Check weights come in a variety of specifications from an 7 in ASTM specs to a E1 spec in OIML RIII 2004.

The real issue is people get caught up in the numbers. THE NUMBERS MEANS NOTHING. read that again if you need to but it's true. For what we are trying to do in reloading is just have as close to the same powder charge thrown as the last time. Hence why the check weights you get with your scale are not the highest of precision to an absolute value. (read that as a lower specification) Again it doesn't matter so long as the weight registers the same deflection on the scale each and every time. That is repeatability

More critical to the operation is not the accuracy of the scale but the repeatability of the scale. Will it read xx.x 99 out of 100 time the check weight was placed on the pan? thats the key. Does your scale read 220.4 grains 9 out of 10 times or 24 out of 25 time placed on the pan? If it does don't worry about the number it means nothing. Repeatability is key.

+1 and a half

[MongooseV8]

You should weigh the powder charges in a single box of some WWB. Ive done it a couple times for fun/curiosity and they run like 41-44 grains in a 308 case.

[JagerDog]

I have to believe the check weights are quite accurate relative to the scale's resolution. 0.4 gr sounds like an awful lot. That said, you could have a cumulative error when placing multiple test weights.

While repeatabilty is king, its valuable to know the discreet value as you may change scales in the future.

Certification would cost more than the weight set.

I don't have a commercial set, but weighed a few objects on a very precise scale in our lab. Recorded their value and that's my set. I've found my various scales to be quite close to each other.

[ar15barrels]

I have been having a problem with my RCBS 5-10 scale so I acquired an RCBS M500 scale. I have a set of Lyman check weighs from .5 to 210.5gr. Using my check weights I'm finding the M500 to have a discrepancy of up to .4 grains at 200 grains. (Weighing 200.4 grains). I'm not sure if the problem is the scale or the weights.

I have no idea where I can go to have the check weights calibrated or certified.
Any suggestions?

https://www.microqualitycalibration.com/#~w9v2c22

[Fire Guy]

Thanks again to all who replied. I know I'm being picky, but I do feel when I'm reading a manual that starts my charge weight at 24.5gr and max's out at 26.8gr I'd like to be close to those values. Thanks again for all the information. You guys are great.