Scaling dilema

[smokindog]

What began as a "piddle and cleanup session" ended up as 3 hours of THIS

Decided to START with the punch line of my "play" (details below). Of the 3 scales I have, I'm most disappointed with the RCBS 10-10. It seems to have accuracy issues as the amount weighed drops, including typical weights for pistol (5.5gr+). It ALSO has a bum gauge, there are two .5's and no .6 readings (see pictures). I NEVER noticed this and now have to go back through my stuff to look for .5 and .6 measurements that might make a difference. Checked all the setup, pivot points, ... Anyone else have any issues? This was purchased last Spring from Midway. Suggestions????


AND NOW FOR THE DOCUMENTATION!!!

I've finally had some time to do some science lab work in my reloading room. My RCBS check weights arrived and I thought I'd compare my three scales.

I've got

A) Triple beam Dial-O-GRAM 310 gram scale (1970's O-Haus, measures to 1/100 gram, most expensive scale and was once available in grains readout as well)
B) Digital XT1500 (Cabelas 1/10th grain) and
C) Balance RCBS 10-10 (O-Haus 1/10th grain)
​

B comes with 2 50 GRAM check weights, C with a 250 GRAIN check weight, and I purchased a RCBS Standard Check Weight kit Contains the follow weights:

2-20 Grain
1-10 Grain
1-5 Grain
2-2 Grain
1-1 Grain
1-1/2 Grain​

Scale A (Dial-O-Gram measures in 1/100 grams)-

• Cabelas 50 GRAM weights together measured 100 grams but individually deviate by +/- 1/10 GRAM.
• RCBS 250 GRAIN weight measured 16.15 Grams (250gr = 16.200g)
• Each 20 GRAIN weight measured 1.275 grams (20gr = 1.2960g)
• The 10 GRAIN weight measured .65 grams (10gr = 0.64799g)
• The 2x20 + 10 GRAIN weight measured 3.24 grams (50gr = 3.2399g)
• The 5 + 1/2 GRAIN weight measured .36 grams (5.5gr = 0.35639g)

Scale B (Cabelas digital measures in 1/10 grains)-

• Cabelas 50 GRAM (a) weighs 772.8 (50g = 771.62gr)
• Cabelas 50 GRAM (b) weighs 770.8
• RCBS 250 GRAIN weight measured 249.8 grains (consistent to above)
• Each RCBS 20 GRAIN measured 19.9 grains (check zero 3 times)
• The 10 GRAIN weight measured 10.0 grains (checked zero 3 times)
• The 2x20 + 10 GRAIN weight measured 49.9 grains (checked zero 3 times)
• The 5 + 1/2 GRAIN weight measured 5.5 grains

Scale C (RCBS 10-10 measures in 1/10 grains)-

• Cabelas 50 GRAM (a) weighs 773.3 (50g = 771.62gr)
• Cabelas 50 GRAM (b) weighs 771.6
• RCBS 250 GRAIN weight measured 249.7 grains (consistent to above)
• Each RCBS 20 GRAIN measured 19.7 grains (check zero 3 times)
• The 10 GRAIN weight measured 9.9 grains (checked zero 3 times)
• The 2x20 + 10 GRAIN weight measured 49.8 grains (checked zero 3 times)
• The 5 + 1/2 GRAIN weight measured 5.6 grains

 

[OKFC05]

Suggestions????

Suggest you get out the original documentation and compare your results to the factory accuracy specifications of each scale.
Some people treat a scale as if it were an absolute reading, but moderately priced loading scales are production items with tolerances, and 0.15 grain STD DEV repeatability is common. Few scales that read to .1 grain are actually accurate to .1 grain.

 

[smokindog]

Yes, I understand that. Precision and accuracy are two different things. The fact that this balance scale seems to drift at lower weights concerns me. Especially at its price point. Plus the double nickel readout. Was just wanting to know if there are others with issues and if it possibly is only a certain production run.

Suggest you get out the original documentation and compare your results to the factory accuracy specifications of each scale.
Some people treat a scale as if it were an absolute reading, but moderately priced loading scales are production items with tolerances, and 0.15 grain STD DEV repeatability is common. Few scales that read to .1 grain are actually accurate to .1 grain.

 

[fredj338]

The only way o know if any scale is reading correctly & accurate, is to verify it with certified check wts.

 

[smokindog]

Yup, that's what I did.

The only way o know if any scale is reading correctly & accurate, is to verify it with certified check wts.

 

[MichiganScott]

It's been years since I spent much time in a lab, but even I recognize that the majority of the figures that you calculated should be rounded up or down. They can not be significant to four places to the right of the decimal when your scale is not accurate to four places to the right of the decimal.

 

[forestswin]

smokin
your disappointment in the 10-10 alone is a good enough a reason to hop on the phone and call RCBS and check out their famed warranty. They used to have you send it to O'Haus directly - not sure what they do now.

My bet is they tell you to pack it up and send it in - they'll check it over, make sure its accurate, tune it up and replace your poise (I wonder if 2 .5's is a collectable item??

if there is one scale you should be able to trust - its your 10-10.

 

[smokindog]

Yes, you are correct. I was just giving the reading, the expected value, and the precision (e.g. when I pointed out measures to 1/10th of a grain)! Sorry, it's the way I was taught to report the data.

It's been years since I spent much time in a lab, but even I recognize that the majority of the figures that you calculated should be rounded up or down. They can not be significant to four places to the right of the decimal when your scale is not accurate to four places to the right of the decimal.

 

[Engineer1911]

More scales = more uncertainty. More check weights = much more uncertainty.

I use a "50 grain" jacketed rifle bullet for a check weight, and throw sufficient pistol charges to approach 50 grains total weight. My system is not perfect but it eliminates a 'lot of uncertainty'. I don't use max powder charges.

 

[dickttx]

"A man who has two watches never knows what time it is."
A man who has more than one scale never knows what something weighs.
Is their anything you load where the variance would make a difference?

 

[Rule3]

I am confused TMI as the texting kids say!

Too many scales. GRAMS? who deals in grams??

Stick with the RCBS, call them about the double nickels as Forest suggested.

I use the Dillion Eliminator (Ohaus) simple balance beam and a set of check weights, Yes, I do have one Blue item!

 

[fredj338]

More scales = more uncertainty. More check weights = much more uncertainty.

I use a "50 grain" jacketed rifle bullet for a check weight, and throw sufficient pistol charges to approach 50 grains total weight. My system is not perfect but it eliminates a 'lot of uncertainty'. I don't use max powder charges.

The problem is most bullets are not exactly the wt indicated. Your 50gr bullet could be off +/- 0.2gr! Not really checking anything, unless that bullet was weighed on a scale verified accurate with cert check wts.

 

[forestswin]

More scales = more uncertainty. More check weights = much more uncertainty.

I use a "50 grain" jacketed rifle bullet for a check weight, and throw sufficient pistol charges to approach 50 grains total weight. My system is not perfect but it eliminates a 'lot of uncertainty'. I don't use max powder charges.

Engineer
While in your "closed-system", I agree, you can give any charge amount any name you want, but if you post something like 2.7 grains of AA #2 as a suggested load and its not based on a standard, you should include a caveat that you're using your own units.

A perfect example of why we shouldn't use loads from the interweb without checking for ourselves.

 

[Rule3]

If we are loading just handguns then check weights of the very light variety are the ones to have. (Like the RCBS package)

They are probably all made by the same company in China so the name doesn't matter.

I zero my scale as it will change just moving it a bit on the counter. I find it accurate just by that. The check weights verify it.

RCBS Standard Scale Check Weights 60.5 Grains

 

[Peter M. Eick]

Interesting information.

So how are you going to handle the situation?

I only have a 1010 and an old rcbs digital. Both give me the same weight for the same check weights. So my two scales and one check weight set are internally consistent.

 

[SMSgt]

Stop worrying about minute accuracy and hope for absolute repeatability. It's not that important if your scale is .015 gains off, it's more important that with the same weight it's always the same reading. Most loads can handle a .015 difference.

 

[KnightTime]

Just my two cents ...
Drop the grams measurement, use grains. I have witnessed confusion between folks using grams and grains interchangeably just because they both start with a "g". While it may not be politically correct in the push for metric measurement singularity, pounds, ounces, grains, inches ... It's what Americans have used for many decades to communicate projectile and powder weight. OK ... I concede drug dealers have made better inroads to metric acceptance in the USA than any push by officials. Maybe I am getting old, but when did the gram become a unit of measure instead of the grain?

 

[Engineer1911]

Scale error

I typically throw at least 10 pistol charges, and weigh the total. If my scale checks at 50.0 grains with a 50 grain rifle bullet and that bullet is off 0.2 grains, than I may have an "error" of 0.02 grains in a powder charge.

I challenge anyone to be able to detect the difference between 2.70 and 2.72 grains of powder in a 38 spl loaded cartridge when fired.

I just don't agonize over the second decimal point in a powder charge or the weight of a bullet; 0.0X just isn't important. Grains are 1/7,000th of a pound. 0.1 grain is 0.00023 of an ounce. This just don't show up on my error meter.

There is significant difference between safe, accurate ammo and perfect ammo. Usually about 10 minutes per loaded round. Either one of my Dillon 550s crank out quality ammo at about 500 ronds per hour. Neither paper targets nor prairie dogs can tell the difference in 0.02 grains of powder, especially if the wind is blowing over 10 MPH.

I agree that 0.010" difference in overall length for loaded cartridge is important.

 

[fredj338]

You seem to confuse 0.02gr with 0.20gr, a big diff.
Fwiw, OAL diff of 0.010", not that important. With handguns, things don't start getting interesting with OAL until you get to 0.030" Ime.

 

[forestswin]

I typically throw at least 10 pistol charges, and weigh the total. If my scale checks at 50.0 grains with a 50 grain rifle bullet and that bullet is off 0.2 grains, than I may have an "error" of 0.02 grains in a powder charge.

I challenge anyone to be able to detect the difference between 2.70 and 2.72 grains of powder in a 38 spl loaded cartridge when fired.

I just don't agonize over the second decimal point in a powder charge or the weight of a bullet; 0.0X just isn't important. Grains are 1/7,000th of a pound. 0.1 grain is 0.00023 of an ounce. This just don't show up on my error meter.

There is significant difference between safe, accurate ammo and perfect ammo. Usually about 10 minutes per loaded round. Either one of my Dillon 550s crank out quality ammo at about 500 ronds per hour. Neither paper targets nor prairie dogs can tell the difference in 0.02 grains of powder, especially if the wind is blowing over 10 MPH.

I agree that 0.010" difference in overall length for loaded cartridge is important.

With your added explanation..my concerns are alleviated .....carry on

My concern is with rounds like the 9mm, where there is a 0.5 grain min to max range on powder charges. Standard check weights are warranted. It matters more the weight is accurate.

How much does your "50 grain" bullet weigh??