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Weighing Powder - How precise is good enough?

 
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  #15  
Old 08-05-2011, 09:41 PM
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Re: Weighing Powder - How precise is good enough?

I don't recall my ChargeMaster beeping. Its been a year though since I've used it

Heck's fire, maybe I can't hear that frequency.
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  #16  
Old 08-06-2011, 05:56 AM
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Re: Weighing Powder - How precise is good enough?

Quote:
Originally Posted by SBruce View Post
So Jeff/Broz, how precise do you go on big cases for extreme long range?
Do you use an electronic or beam scale?

Since we're showing dogs, I just got this in an e-mail. Thought it was hilarious.
SBruce, that ain't no funny Think about our dogs using our long range
weapons to get us!!!! Man!!!! Then again I may think like that because my
dog is a back yard dog...
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  #17  
Old 08-06-2011, 10:41 AM
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Re: Weighing Powder - How precise is good enough?

If you can't get consistent readings and accuracy with a Chargemaster(within a couple kernels or better), there is a problem with it, or with it's use.
I was an early adopter and worked with mine for the first year, comparing every charge weight on an Acculab, which goes another place more accurate. This was a real pain but I stayed objective with it. As a result of this, I was able to see what was going on, tune it's operation, and easily call a bad charge -vs- a keeper.
Eventually there was no further need for the Acculab, and good riddance to it(very accurate and terrible reloading scale).
With my CM I can dispense most charges with greater accuracy than CMs spec at. With IMR7828, this is to single kernel. With something like H322, it's 2-3 kernels.

I think I've seen drifting issues you're referring to, and they are predictable and easy to manage. If you leave a charge on the scale, it will drift away from that charge over time, as the program constantly tweaks for null. It was designed to do this as part of it's self zeroing function(which works well). RCBS should further develop their program to cease nulling when the measure is outside an obvious window. You should see how much an Acculab re-nulls away.. It actually does have to be re-zero'd for every reading! But then, it is very very accurate.
Personally, I'd like to turn off ALL nulling, and read the scale like a beam.
Anyway, you can see that 'fresh' readings are accurate, and dump any charge that is suspect, whether it be an 'old' dispense, or an avalanche kernel fall, to cause overcharge.

My early revision of the CM has a program flaw that switches from zero null, to nulling the entered/desired value. This would cause it to always read a charge as perfect regardless of what it actually was. To manage this & see my actual charge weight, I disturb & re-disturb the pan after the beep/wife whine, and see the weight directly settle within 2sec to the desired value. If it don't occur within 2sec, the desired value nulling will then adjust it.
So knowing this, you get a feel for it quick. If it isn't solid on this, ho-hums around it, I dump that charge & re-dispense. In other words, I pay attention to it just as I would manually trickling.

You have hysteresis with beam scales that also bring you to disturbing the measure/re-reading to gain confidence and accuracy in your readings. Again, it has to be pay'd attention to.
There are good programming settings & DIY mods out there for the Chargemaster. They are worth it. I've provided an externally adjustable trickle speed to mine for tuning with different powders, and installed a straw in the tube.
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  #18  
Old 08-06-2011, 10:18 PM
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Re: Weighing Powder - How precise is good enough?

Yes you can turn of the beep, look in the manual or call the good folks at RCBS they are more then willing to help with any inquiry I have thrown at them.
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  #19  
Old 08-07-2011, 11:47 AM
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Re: Weighing Powder - How precise is good enough?

Some very good points in this thread.

I recently purchased the RCBS CM 1500 scale\dispenser. Mikecr has the CM discernment down perfectly.

Drifting - I have seen a +.2 or +.3 drifting a few times if I walk away and come back 30 minutes later. I have also seen it hold perfectly for longer times so this is just one thing to take into consideration.

Avalanche kernel fall - yup.. I see this happen on occasion. I modify by either dumping the load and redispensing or I remove a kernel or two and re-weigh to make the load useable.

Customized settings -some neat things can be done to one's custom liking. Just make sure you "know" what you are really doing.

The straw thing - I have to research that a bit more.


More Accurate Scales - Reviewing my reloading practices and results, I believe Boomtube has a very clear understanding if there is a need for a scale more precise.

In my reloading experience I also have found there is a "window or range of margin" within the tuned powder charge. That window is almost always + or - .1 (e.g. tuned charge = 57.2; deviation 57.1 and 57.3), but I have seen it + or - .2 (e.g. tuned charge = 57.2; deviation 57.0 and 57.4). Even of just recently with 4 different rifle loads tuned, stepping out of the tuned load +- .3 or more not only opend the group, but for a couple of rifles, opened the group significantly more than 1".

..but ... I have found one exception to this experience result. If the bullet seating is "on or into the lands", for some reason the groups barely if any changed even out at 200+ yards. Again with my experience, the powder charge can be modified by even by as much as 1.5+ grains and the groups stayed almost the same.

I understand Mikecr mentioned one expert found that even a "kernel" deviation made a difference ...but I am going to side with this discernment -->

"...small internal variations in individual case volume, differences in individual primer heat, even changes in the ambient temp on powder burn rate produces more potential velocity variation than truly tiny powder charge differences."

not to forget the personality of every single rifle

Just a thought: Stereo makers make stereo equipment that have specs that a human ear cannot hear ever; but they charge you for it "because it is there".

So use your own discernment but make sure you aren't drinking some kool-aid. There are some kool-aid makers out there that will next try to sell us "kernel" splitters.
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  #20  
Old 08-07-2011, 01:45 PM
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Re: Weighing Powder - How precise is good enough?

Quote:
Originally Posted by Eaglet View Post
SBruce, that ain't no funny Think about our dogs using our long range
weapons to get us!!!! Man!!!! Then again I may think like that because my
dog is a back yard dog...
Wouldn't it suprise the heck out of ya if you walked into your bedroom and saw this? Lets just hope that beep doesn't give them an itchy trigger paw too!
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  #21  
Old 08-08-2011, 03:05 PM
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Re: Weighing Powder - How precise is good enough?

When working up a load, I use a B&M measure to get close, then trickle up to the exact number. When loading to shoot, my measures get to within .10gr or so. The larger the load, the less important a consistently accurate load becomes. For example, for rifle loads of 36.0 grains of something, a load of 36.1 or 36.2 isn't a consideration unless you are dealing with max loads. The difference is <.10% and inconsequential.
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