Scale accuracy and precision, how much is needed?

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hounddawg

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How accurate and how precise does your powder charge need to be? There is a thread looking for scale recommendations right now and the prices for the scales range from $25 dollars to well over $600. A few months back I bought a $25 dollar scale from Amazon and tested it for repeatability (precision) and did the best I could to check it's accuracy against my modified beam scale since I do not nor will I ever own a certified lab scale and have no easy access to one.

This is a screen capture of the spreadsheet on which I weighed three weight different bullets 5 times each to check the precision to see how repeatable readings were. The second pic is a 600 Yard target shot on a very cold (for me) 32F morning. All loads were loaded to .01 gns plus or minus .01 gns

The load has only been tuned to .3 gn increment and a seating depth test Berger style using .025 jumps from .100 off to on lands. Out of 60 shots that day I only had a single flyer to the right on the waterline. I called that one when I shifted my weight with my finger on the trigger. The other two targets were very similar to this one, good but not great scores with low X counts. I think a fine tuning of the seating depth can tighten that group up and boost the X count

So how accurate/precise a scale do you really need for loading?
 

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In my opinion, reloading scales don't need to be .1 or even .2 grains "accurate", but they must be repeatable.. If I weigh a known weigh standard, it really doesn't matter if it reads .2 grains off the known laboratory weight as I don't load near maximum charges, but it must weigh the same every time, no variations. I always start my reloads with book starting loads and work up. If a charge works well with my reading of 9.9 grains, it really doesn't matter if the actual "laboratory" weight is 10.0 or 9.8 as long as the scale measures the same every time...
 
I've been in this business of reloading a long time. My advice to those new in this endeavor is as follows:

1. Use a beam scale for repeatability as the gravity of planet earth seldom varies at any one location such as your place of reloading.

2. Digital scales will drive you crazy trying to measure exact loads of powder. They drift with temperature, voltage, age, rf interference, and other factors. They are useful for quickly separating bullet or case weights but little else.

3. Yes, the $1000.00+ digital scales can overcome the repeatability issue, but the cost hardly seems worth the cost.

Ignore the above and I'll bet you buy at least three digital scales before you go back to using your beam scale for consistent accuracy in reloading.

Just my opinion....
 
+/- 0.1 gr. seems to be the norm for most reloading scales, whether digital or mechanical. 0.1gr. represents an error of 2.5% for a 4 grain load and a 0.25% for a 40 gr. load.

Once they settle on a load, many target shooters achieve excellent results without weighing each charge, or even adjusting the powder measure with a given lot of powder.

I've gotten use to a low cost digital scale (and their behaviors), and rarely use my RCBS 10-10 anymore. Since my loads are generally below published maximums, I'm not worried if my scale is off by 0.1 or 0.2 gr.
 
Well as gravity is consistent for where you are, your results will be consistent. So if your load is 40.5 and in SI its 40.32156 as long as the scale delivers that same load (or 1/10 of it) each time, you are good. Strike 1.

Do they drift, yes they do, not as bad as indicated but yes. That is what a zero button is for. I supposed its individual but if you check your pan weight and zero when it goes off a tench, then you are good. Strike 2.

In cross check my dispensers are within a 1/10. I got them all on sale. I don't have $1000 total in the 3 and two dispense powder as well. Strike 3.

My opinion of course.
 
Finally! It seems that the above truly understand reloading scale needs.

All the new reloaders that think they need to have a reading to .000000000001
are killing me.

I have an original PACT electronic scale that I purchased right after they came out and PACT was making scales for it seemed everyone.
Still works as well as it did new IF you let it warm up enough.

Also have an RCBS (Ohaus) 1010 that is at least 30 years old.
I use one to verify the other and they always have.

Both were guaranteed to be accurate to 0.1 grain. Good enough for over 30 years and unless something happens they will be good enough for the next 30.
 
Some electronics are sensitive to temp it seems. I have one that goes berserk if the temperature in the shop drops below 60F. Even after heating the place up it takes a few hours to stabilize. Two others no problem at least down to 50F and of course my Lyman beam could care less if it was sub zero

I think the biggest contributor to consistent velocities is the powder choice for not only the cartridge but also the barrel. Find the right one and you can load with a rotary throw and be good enough. Maybe we need a thread on that
 
Not a purely scientific experiment (lots of undefined variables) but a rudimentary example of powder measurement methods.

Part 1
Part 2

Things I noticed:
The Prometheus and Auto-trickler tended towards the lowest SD. Although the Harrell powder drop had the lowest SD in one case. They used a lab scale to verify all the drops. (Hmm that alone makes you wonder about their results.)

So your take is what you use is the best? Or is it that anything is good enough?

My suggestion, satisfy yourself.
 
Not a purely scientific experiment (lots of undefined variables) but a rudimentary example of powder measurement methods.

Part 1
Part 2

Things I noticed:
The Prometheus and Auto-trickler tended towards the lowest SD. Although the Harrell powder drop had the lowest SD in one case. They used a lab scale to verify all the drops. (Hmm that alone makes you wonder about their results.)

So your take is what you use is the best? Or is it that anything is good enough?

My suggestion, satisfy yourself.
Click to expand...

Thanks for those links, I subbed to their channel

On the target portion of the second video for the 6X47 Lapua the Harrels had the smallest group @3.376, Auto Trickler in second with 3.475, Promethius @3.621 and the RCBS CM @4.114.

It kind of makes you wonder doesn't it? In particular when I am getting just as good results over the chrono from a 25 dollar scale. If a load is developed right it should be a flat spot in the velocity curve. If you cant go up or down a tenth with less that a 10 - 15 FPS ES you need to find another node or powder or bullet. Speaking strictly for long range of course. Close range SD and ES really doesn't matter

BTW that 6x47 can shoot, I am hoping my 6CM will group like that. :D
 
The theory that beam scales are infallible and always repeatable has not been my experience. I have an rcbs 505 and i use the calibration kit to check it frequently. Not sure if it is a resolution issue (<.1grains) or just design but there are charges that seem to vary based on how i place the pan on the scale. I double weigh every charge, 1 from the auto dispenser and then i put it on the beam.
 
I have devices that can detect a single kernel of powder difference in charge. My “good” loads can vary a lot more that that and still have the same POA/POI relationship.

Some pretty good ones are temperature sensitive so charge weight might be less important than the conditions I am shooting them in.

I guess it’s all important, if it’s not as important as other stuff, then it doesn’t matter as much.

Groups tend to shrink when the human element is removed. That’s why unlimited benchrest guns are machines vs rifles.
 
I shoot at Keblys Rifle Range which is home to the annual industry Super Shoot. There are as many as 300 competitors out there for this event. Each paid shooter receives table space in any of several large buildings. The Super Shoot spans several days and something I noticed in the bench rest community when these guys setup their tables for loading and cleaning plus general maintenance you never see a scale. Just about all of them are using a Harrell's Precision Powder Measure. While I am not a bench rest type I enjoy getting out there during the shoot just meeting and talking to people. These guys simply do not use a scale. Row after row of precision powder throws is all you see on their benches.

Now I understand the F Class guys are into precision weighing of powder shooting 1000 yards in matches. I just found it interesting what these bug hole shooters do.

Me? I have and use several digital scales but also cling to my ancient Lyman M5 or my RCBS 505. I have an old (maybe 25 to 30 year old RCBS Digital and when used as it should be it does fine and I have been making some good consistent ammunition using a new RCBS Chargmaster. For years I was happy in rifle with +/- 0.1 grain, mostly 30-06 Springfield and 308 Winchester out to 500 meters. Like others I want repeatability.

This year the Super Shoot runs from May 21 through May 24 so anyone in the north Ohio area who would like to just visit, hang out and check out what vendors have let me know as I enjoy getting out there for a day.

Ron
 
The Super Shoot spans several days and something I noticed in the bench rest community when these guys setup their tables for loading and cleaning plus general maintenance you never see a scale. Just about all of them are using a Harrell's Precision Powder Measure.
Click to expand...

yet those same 100 yard benchrest shooters will obsess endlessly over the case neck thickness. Then go to the long range benchrest matches and they will be measuring to the kernel. Jump on a ballistics calculator and you will see why, a 20 FPS difference between two rounds is larger than the world record group at 300 and out.

Regular people like me are still hoping for 20 shot 1 MOA groups at 300 and out
 
Hounddawg:
"yet those same 100 yard benchrest shooters will obsess endlessly over the case neck thickness. Then go to the long range benchrest matches and they will be measuring to the kernel. Jump on a ballistics calculator and you will see why, a 20 FPS difference between two rounds is larger than the world record group at 300 and out".

Yes, exactly and it becomes interesting to watch. I would also fall into the regular people group. :)

Ron
 
I'm using IMR 4064 loading for my 308 . Eack kernel weights .02 of a grain , I double check my loads from a CM 1500 to 40.8 then check in my GemPro to 40.84 . Groups have been very consistent for a long time . Would have to load from 40.8 to 41.0 to see if things change even with that slight shift . I stopped tweaking my reloads , kind of scared it go back there .

I'll be away until Monday night , going to Tampa to spend some time with my Son , he's being deployed for the third time to Afghanistan . Will be holding my breath for 9 months until he comes home . Some things never change . Will check in when I get back . Be Well .

Chris
 
By the way, in a pique of annoyance, I checked my two electronic powder dispensers against that Ohaus 505 (yes I will keep it and yes it goes back a few years)

The Hornady was dead on per its set dispensing.

The Lyman was withing a couple of tenths (and just turned back on from a power outage shutdown) - .2 high.

I can live with that, I am not going to the equator anytime soon.
 
You can to throw accurate charges. Thats easy. Although thare are alot of things that can make a diffrence in accuracy. Cases are a hot topic. Thare are alot of things to measure on cases. How about your primers. Watch what others are doing with cases. But don't go there without proving. Bullets same thing. Thare are a lot of powders out there. Try some out don't just accept that the next guy has is what your rifle wants. Practice practice practice. If you want to be good. You are the one that needs to get it right for your rifle. Im not a pro. Ive shot at Georges place back in the 70's Thats the place to go. You sound like you have the bug. Start measuring and Practice. Good luck
 
cw308:
I'll be away until Monday night , going to Tampa to spend some time with my Son , he's being deployed for the third time to Afghanistan . Will be holding my breath for 9 months until he comes home . Some things never change . Will check in when I get back . Be Well .
Click to expand...

You have a safe trip and enjoy your time together. Pass along a Thank You to your son for his service and wish him well from an old Marine.

Ron
 
Perhaps its all mental. Do whatever it takes to calm the obsession so that mental focus stays on the job at hand. I don't think about case prep or load weight variation, or the latest bullet to come out when I'm shooting. I will never be as accurate as my case prep. I will never be as precise as my load weight. I will never be as sorted as my bullets or brass. But nothing gives me the immediate feedback that shooting does except the eye roll my wife gives me.

In shooting perhaps its not the journey but the destination that matters most, at least in the short run.
 
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