Weighing Powder - How precise is good enough?

[jdbove]

I've been more or less forced to look into replacing my RCBS Chargemaster electronic scale for a reason you would never guess. It seems that the 'beep' tone that the scale issues is on the exact same frequency as the warning tone for our dog's underground electric fence, and no matter how far away I try to do my reloading the poor animal is freaking out (along with my wife) until I am finished. At least it gives me a pass to look into upgrading.

This is where it gets tough. As is typical, I've been reading everything I can find online before choosing a replacement, and also as is typical, am reminded once again that when it comes to precision instruments, you get what you pay for.

I had an interesting conversation with the very knowlegeable owner operator of Precision Weighing Balances (www.balances.com) when I called to ask for his advice. It seems he gets a lot of phone calls from 'gun guys' and quickly becomes frustrated with our refusal to acknowledge that if we want to weigh powder charges accurate to .1 grain or less, we are going to have to spend at least $700 on a lab balance.

The gentlemen rapidly dismissed ALL 'strain gauge' based balances as 'junk' and insisted that for this level of precision, only an 'electromagnetic force restoration' balance will suffice. These units START at roughly $700 and rapidly escalate in price to well over $8K. Not the biggest fan of us 'gun guys' he doesn't quite understand how we are willing to drop multi thousands of dollars on 'monster weapons' but won't pony up for the right balance to optimize its function. He pleaded with me to watch his YouTube videos on these subjects (search 'balancesdotcom' on YouTube) and 'spread the word' to the gun guys so he will get fewer inquiries that lead to no sale due to sticker shock.

I think that we can all agree that when it comes to weighing charges, uniformity between samples is probably more important than the true absolute weight of any given charge when creating a batch of loaded rounds. This notwithstanding, there will also be those of us who desire (or require) a very precise measurement of the charge weight as well.

So there it is...how precise does this element of our pursuit of accurate long range shooting have to be? Must we all pitch our RCBS/Hornady/Sinclair etc. 'junk' in favor of a piece of true laboratory equipment?

With my luck, a brand new fancy high dollar lab balance will produce the same **** beep frequency as my current one, only LOUDER. My wife will make me move out.

 

[SBruce]

I feel sorry for the dog!

No, seriously; a good powder meter (thrower) will get you really really close with most powders. I take it one step further and then trickle in to within 1/10 grain on my "normal" reloading scale.

I truely believe that weighing charges to absolute true precision isn't necessary, and may not even be beneficial. The idea of finding a load in the sweet spot is that a couple tenths variance will not affect poi. Heck, I know alot of people that don't bother even trickling to the scale, they just throw the charge with a good quality meter and then seat bullets. There's supposedly alot of world class record groups shot with charges that were only metered, never weighed.

 

[boomtube]

The (other) old guy is mostly correct. Fact is, we really don't benefit from high precision in charges. Few shooters will ever see any difference between charges weighted to +/- .0000001 grain and those within +/- .2 or .3 three grains of powder. He77, the normal varations between individual cases and primers and the ambient temperature changes on the range make that much difference!

 

[BlackKnight755]

JD,

I'm not positive on this but I think theres a way to go into the settings of the RCBS chargemaster and turn off the "beep". I remember reading a thread some time back where people were going into the setings and changing all kinds of default settings and setting them to their liking and I want to think that the beep delete was one of the things that was an option. I am sure that a call to RCBS tech help and they would be able to tell you. They are a great bunch out there. I called the other day to order the cap that goes on my old bullet puller and they sent me one the same day for nothing. Have had other issues also that was handled free of charge... 'course like you said, you do have an excuse for an upgrade now, so you may not want the old scale. BK

 

[Broz]

 

[Mikecr]

I think the forced balanced approach is a good one. Now if 'balances.com' can produce a better RELOADING SCALE with it, that also charges cases to desired value, and automatically aggravates the wife, but not a dog when finished, we could consider the cost for more of what it's actually worth to us.

I've used high dollar scales at work and at home. They are not good reloading scales.
That forced balance approach would likely come with costs, as everything does.
I can picture it as sensitive to sound. As in every time your wife whines about anything your scale would struggle to null..
My Chargemaster just ignores her. It is my hero.

 

[Trickymissfit]

The (other) old guy is mostly correct. Fact is, we really don't benefit from high precision in charges. Few shooters will ever see any difference between charges weighted to +/- .0000001 grain and those within +/- .2 or .3 three grains of powder. He77, the normal varations between individual cases and primers and the ambient temperature changes on the range make that much difference!

wasn't it Bruce Hogdon that once said that +/- .15 grain is all that matters? That's a .3 of a grain window. I do think some powders benifit more from being precisely measured than others do. (faster burn seems to warrant a little more precision in my book). Also a few years back the guy that won the Super Shoot at Kelby's said he just threw the powder out of an old Homer Culver built Lyman #55, and I think he said he was shooting in a .25 grain window with his loads.
gary

 

[venom600]

The level of precision that you care about should be measured (by you, not your scale) in percent, not grains (or tenths of grains, even).

.1 grain is only 1/10% difference in my 300RUM (using a 96.5g charge)

.1 grain is 2% difference in my .40 S&W (using a 4.7g charge)

Whether or not that level of precision is necessary for *your* load is an exercise for the reader. But, just some food for thought....

--Ben

P.S. Jeff, that picture is hilarious. My dad puts ear muffs on his lab when they're in the wood shop together. The lab doesn't care a bit......pretty funny to see him wandering around or laying in the shop with his big red shooting ear muffs on.

 

[Mikecr]

It is also a matter of the load itself.
When loaded to extreme pressures, powders burn faster, the pressure peak narrows, and barrel timing becomes more or less constant, with only little things like air density(that piston of air in the bore) to screw with it..
A 6PPC loaded wide-***-open easily burns all of it's powder in a 21" barrel, and there ain't a lot you can do about it(including screw it up). It's charges are not typically weighed, because they don't have to be, given it's sliver of application..

But a 6PPC is not a long range HUNTING cartridge, and hunting cartridges cannot be run at 6PPC extremes -ever. Well, until a better barrel steal is invented..

I agree that powder weight tolerances needed for hunting cartridges is tied to capacity. This can be seen using QuickLoad, and QuickTarget.

 

[SBruce]

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.

 

[boomtube]

"..wasn't it Bruce Hogdon that once said that +/- .15 grain is all that matters?"

Don't know about Bruce but that sounds like him. My comment is based on my own observations. Obviously (or it should be) the tolerable variation will depend a lot on the quanity of powder being burned so that changes a bit with case size.

Thing is, ALL powders burn best (that is, most consistantly) within a fairly narrow but easily and clearly identified pressure range. A properly tested and chosen load will have what I call a "window". or tolerance range, within which small variations mean virtually nothing to accuracy - that's why BR shooters rarely bother to weigh charges and sometimes don't even know the weight of their charges. If we take the time to find the full width of that good performing range, typically .3 to .5 gr. for mid-size cartridges, and load in the middle of it small variations won't matter and the frequency of 'unexplained flyers' will diminish. Only when loading on the ragged edge of the window will small variations in the wrong direction cause problems.

IMHO, those who pay big bucks for a Promethus, etc, scale rather than properly developing a good load that's insensitive to tiny variations are wasting big bucks for no good purpose.

 

[Mikecr]

Well given that this is a 'long range hunting' site there is still ES to be considered HERE.
There are tolerant cartridge/load combinations(OCW), but often they are less than suitable over a range of distances. They can produce tiny little short range groups, and suck to hell for distant accuracy, unless also benefiting with low ES.
Afterall, barrel timing and velocity are two different things that don't hold a linear relationship.

You can hit on barrel timing that provides exceptional velocity tolerance -at one distance. An upswung muzzle at a lower velocity, etc.
But this would prove to be a wreck at some other distances, and it would also require a tight charge tolerance and shooting condition(or tuner) to hold.
Many competitors have seen that load development for this timing -at their intended range, is worthwhile.

Now with LR hunting cartridges it is even more difficult to get a velocity tolerant load AND low ES. Our ranges are not set, our muzzles move a lot, and our powders & pressures are relatively slow & low.
So tight tolerances on charge weight(w/resp to capacity) isn't a bad idea.

David Tubb implied benefits to charges taken to the granule with his 6xc, and he promoted use of Prometheus(which does).

 

[SBruce]

Mikecr is correct that we not only need a tolerant load, but also a load with low ES in velocity. If we're only shooting to 700yds maybe 800 yds, then low ES isn't quite as important as it is when shooting to 1000 yds and beyond.

Perhaps Tubb is advocating the labratory scales now, but he wasn't when he produced the dvd on reloading for highpower that I've seen. He used a powder meter and standard scales, and was getting single digit SD's with those tools (according to the video anyway).

I am not trying to say that it's a waste of money to get a labratory scale........don't know for sure, never owned one........but I believe lots and lots of people have gotten great results without one. Fact is, I know a guy that is a 1000 yd Club member of the VHA, and he did it on a prarie dog. He doesn't even trickle his charges......simply uses a meter and calls it good.....I specifically asked him that question when we were talking about Varget vs H380. I told him that I'd rather use H-380 because it meters like hot butter and that I have to trickle Varget onto the scale (which takes alot longer)............He said that he doesn't trickle it even with Varget. He just sets the meter to throw an average charge of X grains and calls that good.

Specifically speaking of the RCBS chargemaster scale........how accurate are they compared to a "normal" balance beam scale..?? In my limited experience, not very accurate. I can put the same case on my Chargemaster scale 5 different times and get 5 different readings, within a few tenths every time but not the same. Both my balance beam scales will repeat exactly with that same case, every time I weigh it...........Yet, some claim to get excellent LR performance with the Chargemaster Dispenser.?

 

[boomtube]

"...tight tolerances on charge weight(w/resp to capacity) isn't a bad idea."


A bad idea? No, it's not bad, as such. Extreme spread IS important for long range shooting but there's MUCH more involved in obtaining low ES than precise duplication of charges. I don't think that even counting the individual kernels of powder for truly exact charges will make the difference in ES that several other factors in developing a load will exceed.

Part of the obsession with scale and powder precision is just because it seems so logical but getting more precise than maybe .1 gr. is largely pointless - maybe entirely so - because 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. IMHO.