July 28, 2018, 10:41 PM | #1 |
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Weight vs volume
Which is more important to obtain consistent loads? It seems to me that ball or flake powders which measure well out of powder throwers are more consistent in weight as opposed to stick powders. However, if you measure stick powder by weight, the amount of volume in a case (e.g. necked rifle case) is less consistent. Since stick powders have different size "sticks", I can't have both consistent weight and volume. Any thoughts?
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July 28, 2018, 11:06 PM | #2 |
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I use a scale to get perfectly consistent weight with stick powders. A "trickler" does the job.
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July 28, 2018, 11:52 PM | #3 |
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Weight vs volume
Calories of energy available from burning the fuel depends on the compound and mass; the burn rate depends on the volume consumed by fuel and volume available to expanding burning gasses. The right answer is both... but the density of your metered volume would have to be very consistent and we know a stick powder is not. A compressed load eliminates some of the uncertainty because the available volume for ignition is consistent.
For basic plinking loads use volume. For accuracy or consistency use mass because controlling the total calories is the bigger effect, the rate of consuming them is secondary but not unimportant (especially in short barrels like 3” handguns where it’s possible you’re not fully burning the powder under pressure, and maybe you need to change powder if that’s the case to a different burn rate). I personally prefer powders with smaller size so that I can meter volume and double check weight consistency. I do pretty well at low 20s deviation in velocity with Accurate LT-32 for 5.56 and 308 Win and a powder thrower because it meters so smoothly. Andrew - Lancaster, CA NRA Life Member, Calguns.net contributor, CGF / SAF / CRPA / FPC / USCCA member Last edited by lordmorgul; July 28, 2018 at 11:58 PM. |
July 29, 2018, 07:16 AM | #4 |
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depends on who you ask. Short range 100 - 300 shooters get .1 and less groups from a powder throw no trickling required so they prefer volume. Long range shooters measure to the milligram using lab grade scales and get 1 inch groups at 1000 yards
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July 29, 2018, 07:40 AM | #5 |
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Powder charges are based on "weight" but are often dispensed by volume as an expedient. Under no circumstances should volume be the only unit of measure for powder charges.
I've found that multiple powders I've tried for .223 loads have measured out to very similar volumes often requiring only minor tweeks of the measure. Finding a "sweet spot" of powder filled case capacity for a given cartridge makes further loading much easier. |
July 30, 2018, 01:01 AM | #6 | |
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After that I'd say it depends on the need . The only time I weigh every charge on a handgun charge is during load development . After that the scale and charge is checked with check weights and I throw the rest while weighing every tenth throw or so . That's because I'm not trying to shoot sub moa at 200yds with my M&P shield . I hit what I'm aiming at with just throwing my handgun charges why start making it harder to load those when "I" wont notice the difference . On the other hand I weigh almost every rifle charge regardless of cartridge except my 223/5,56 plinking loads that I use H-335 with . H-335 throws so well for me I have no issues doing so . Most all my other rifle powders are stick powders and they just don't throw all that well . The two worst I've found are IMR 4064 and IMR 4350 . I can't get better then a +/- of .3gr or ES of .6gr with those two powders . That's a lot , especially in a small case like the 223 . In a 50BMG I'd likely not care one bit of a .6gr variance but in a 223 that's 60fps+ which will blow up your ES/SD .
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July 30, 2018, 03:53 AM | #7 |
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Stick (rifle) by weight, ignoring volume diff's. I'm not a high volume rifle shooter.
Handgun powders I meter by volume. I have settings recorded for each charge combo. I just dial in the setting on my meter, check that it's within .1 grain and run, checking every 10th with a scale. I do use small stick handgun powders like N340 and N310 in my meter with no problems. |
July 30, 2018, 09:12 AM | #8 |
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You can throw stick powder accurately by the way you work the press. Take the handle up to fill and then bump the handle a couple time's. You'd be surprised how accurate you can be. But it does require the same bump every time. I have done it and find that now and again I don't do it the same and come up a bit short. So I always set the dispenser a few tenth's low and trickle up loads. If I was doing a lot of rounds at one time I'd consider using a ball powder. They measure very well. To see why bumping works, throw a charge of stick powder in a case that will pretty much fill it. Look and see where the case is filled to. Now put your thumb on the base and a finger over the mouth and tap on the side of the case several times then look in the case and the same charge will not come up quite so fat. You have settled the stick powder.
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July 30, 2018, 11:03 AM | #9 |
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You see some reports of volumetric measured stick powder actually being more consistent than what is measured by weight. it is true that less consistent weight means you are not throwing the same amount of stored energy, but stick powder throws get their different volumes by how the sticks packed in the metering chamber of the powder measure. The more tightly they pack, the harder it is for the ignition flame to pass through the powder so the slower their burning rate gets.
Hatcher reported that one year (1920's) he tested two powders with burn rates similar to the later-developed IMR 4320. One was a short stick grain that the arsenal loading machines could meter to within a spread of 0.6 grains, while the other was a coarse stick which the equipment could only hold to a spread of 1.7 grains. Yet the latter powder's ammunition was consistently more accurate and wound up being that years NM load and several records were set with it. Apparently packing and burn rate compensated nearly ideally for charge weight differences with that powder in the .30-06 with M1 Type match bullets. This tendency of stick powder burn rate to change with packing density makes it harder to be sure what will happen. The 1995 Precision Shooting Reloading Guide had an example from, IIRC, Dan Hackett, of a stick powder load that worked fine when the author loaded it at home, but caused sticky bolt lift when loaded at the range. He finally tracked it down to the vibration in his vehicle packing the powder down while he was driving to the range, lowering its burn rate. Weighing has its limitations, too. The Norma manual points out powder burn rate can change as much as 12% depending on what humidity it is kept in. It can hold up, IIRC, about 1.5% water by weight, so a high humidity (>80%) charge weight will rob you of that much energy content as compared to a desiccated sample of powder. So, what's a body to do? Well, for one thing, you want to keep your powder in constant RH. Norma says they keep it between 40-60% RH until it is packed and shipped. 70% is another common storage number for powder. You mainly want to pick a number you can reasonably maintain and stick with it and keep any ammo you load in advance in that same humidity as Norma points out the powder in unsealed cartridges equilibrates to storage RH over about a year. Second, use a powder that provides peak accuracy (obviously) and that fills the case well. I think this is one of the secrets of Federal's .308 Win Gold Medal Match load with the Sierra 168 grain bullet. The charge of 43.5 grains of their special lots of IMR 4064 is about 0.5% compressed. That locks the powder grains in place and prevents vibration from compacting the powder and changing burn rate. Note that this does not appear to be an issue with spherical propellants as they don't pack appreciably (the reason they meter consistently). I once pulled down some Winchester Supreme .308 Win 168 grain bullet match loads that had what looked like 748 in them. They charge weight spread on my lab scale was an astonishing 0.05 grains. But it didn't shoot as well as the Federal, which had a 0.4 grain spread in the sample I pulled down. Third, when I'm trying to make super-precise loads with stick powder, I use both volume and weighing. I have JDS Quick Measure that is very consistent with stick powders. It guarantees no more than 0.2 grains error, and I find it comes closer to 0.1 grains in most instances. Zero you scale with the primed, empty case on it. Throw the charge and keep only the ones that match weight as exactly as the scale reads. You can also throw an intentional half a grain low and trickle up on the scale to final weight on the assumption that adding that last little bit won't affect the packing under it, but I haven't tested it to see if it can settle the powder a little or not. The advantage of the volumetric measure here is that it not only sorts out the powder density but if you leave it set for the same powder it will average at the same energy density of charge, whether the powder has changed moisture content or not. Fourth, if you want to dispense powder by weight and you can keep your humidity consistent enough, then you want to be sure you get consistent packing density when you move the powder from the weighing pan to the cartridge case. This means picking tha pan up and using the same powder funnel, held at the same angle and pouring powder into it at the same rate every time. Just like working a powder measure, consistency of motion and method get you consistency on the target paper.
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July 30, 2018, 11:47 AM | #10 |
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I thought about this a bit last eve and here is what I think
If you are shooting beyond 300 then a consistent velocity matters. I can take 50 cases, prep them identically and trim all to within .001 of each other. Seat all primers perfectly and load all with powder measured to within a kernel of Varget. Take them to the range and fire them over a chrony and get all sorts of extreme spreads and standard deviations. I have also load tested where maximum velocity may be no more than 25 FPS for four or five tenths of a grain from lowest load to highest then you go up a tenth grain more and have the velocity jump 50 FPS. My theory is that each cartridge and bullet will have sweet spots where the case fill is perfect for the primer and powder burn rate. Once you find that sweet spot the weight/volume can be off a bit one way or the other and the ammo will perform at any distance I will be doing a new load development later this week weather permitting and if I find one of those wide flat spots I will make a thread with pics.
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July 30, 2018, 11:47 AM | #11 |
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Smokeless powder is weighed by weight, not volume, regardless of the shape of the granules. Black powder is weighed in grains but by volume.
Some powder charges are compressed. Means the bullet packs the powder into the case. Compressed loads are nothing to worry about. They have nothing to do with volume though. The whole thing isn't something you need to worry about as long as you follow your manual.
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July 30, 2018, 02:19 PM | #12 | |
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Mostly, people actually measure powder by mass, not weight, even if their scales are calibrated in grains. A spring scale will measure actual weight, but a balance or an electronic scale calibrated with check weights is actually measuring mass and giving you what the weight would be in an ideal 1 g, regardless of the exact gravitational value at your location. A balance always balances when the pull of gravity applies the same torque to both sides of the knife edge and will give you the same result on the moon that it does on earth, where a spring scale will not. Powder may be dispensed by mass, however, it is also dispensed by volume based on the idea its bulk density will remain constant enough to do that and still get reasonably close to the same weight in each charge. Virtually all commercial ammunition is charged with powder dispensed by volume. You need only visit a gun store to get a tiny idea of how much volumetrically dispensed smokeless powder is really out there. The American public consumes around 15 billion rounds of volumetrically charged commercial rounds annually.
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July 30, 2018, 04:44 PM | #13 |
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Ok, now I am going to have to take some of my hard earned dollars and buy a 20 pack of 30-06 or 308 and see what he weight variation is.
And is there any explanation as to you rely measuring mass and not weight with a balance or electronic scale? Something that does to require physicists, trigonometry, I ok with simple algebra .
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July 30, 2018, 04:46 PM | #14 |
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And has anyone taken the SAME power, tested it via volume and got a node, then done the same with it via a scale and come up with a difference of accuracy?
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July 30, 2018, 08:52 PM | #15 |
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put 5 woodworkers in 5 shops and tell them to join two pieces of wood together and they will use 5 different methods and all are correct. If it works for you do it, if it doesn't then change to something that does
reloaders love to overcomplicate. In 1973 Mac McMillan shot a .009″ five-shot group in a 100 yard benchrest match. That record stood until 2013. The amazing part is he shot it without a electronic scale or a 1500 dollar induction annealer
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July 30, 2018, 09:27 PM | #16 |
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RC20,
Yes, I believe the AMU armorers did some testing in this regard, but I can't recall their conclusions. I'll check with a couple of sources on that. The topic has come up in numerous articles and forums over time and they are easy to find. In general, the humidity changes and influences that cause errors when weighing are smaller than the ones some measures can bring about with some measures, but not all. If you are throwing spherical powder, for example, and are keeping 50-grain charges within 0.1 grains, that's only 0.2% of charge, which is less than the error changing RH value can bring about. If, for example, your powder gains 1% over an 80% RH swing, then a 16% swing in RH will produce that 0.2% change in weight, or 32% for a plus and minus 0.1-grain swing, so weighing is only director be more accurate if your humidity swings less than that. The reason weights are given in most manual data instead of volume is that bulk density from lot to lot can change by up to ±6% with some powders (Western publishes this for Accurate Powders), so just going by volume gives you that potentially much larger starting load error. You always want to start out developing a load for a new lot of powder by weight first, for that reason, then determine the bulk density for your lot to make volumetric changes. The mass thing is simple. Imagine the basic two-pan balance like the statue of Justice holds up above her blindfold. You put two equal masses that weigh, say, 60 grains in each pan and they will balance and the pointer will be on the zero mark. Put the balance on the moon and the two equal masses will still balance even though they now only weight 10 grains in the moon's weaker gravity. This is because they pull the scale pans down with equal for, even though that is only 1/6th of what it was on earth. So the balance measures mass. If it is a beam balance, for the same reason, it will still balance on the moon: the mass in the pan and the masses of the counterpoise weights are the same and their weights are equally smaller, but the weight graduations will still say 60 grains on the moon even though the weight up there is actually 10 grains.
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July 31, 2018, 06:26 PM | #17 | |
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When it was done, while there were some common aspects, no two did it the same for something like 6 or 8 different parts of it. I came away thinking that what gets tiny groups was faith. As long as you believe you will get tiny groups you pick a series of steps and processes and stick with it, you get tiny groups.
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July 31, 2018, 06:28 PM | #18 | |
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Ok, first take is do not reload on top of Mt Everest!
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August 1, 2018, 01:21 AM | #19 |
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Let me try to explain some things that may have already been said. First, the sticks will not be inconsistently sized, every stick will be within a few hundredths inch in length and practically identical in diameter, and since this stuff is mixed in lots of a thousand or so pounds, your lot will be as consistent as it possibly can be. Any deviation between one charge and another is only because of the way they stack up in the measure.
In theory, measuring every charge to the tenth of a grain should give you greater accuracy. In reality, unless you are deviating by .2 grains or larger, it is very unlikely that you will find accuracy issues that can be attributed absolutely to your charges. When you have squeezed every last variable out by buying better bullets, bedding and tuning, finding the best possible load, then, and only then, should you worry about whether you're getting exactly to the .1 grain measurements. You will never, ever be able to tell if you're shooting old betsy with a randomly selected load from a manual.
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August 1, 2018, 09:31 AM | #20 | |
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August 1, 2018, 09:42 AM | #21 |
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I did a small test yesterday of my RCBS Chargemaster 1500 vs my Hornady Powder throw. It was no surprise that the throw did poorly with stick and course flake powder but with the fine ball it was very accurate. It did poorly with the WIN 231 which is a fine flake but the static with that powder was horrible. Even used dryer sheets were no help. The Chargemaster was consistent all powders in so I only tested a few
Fifteen charges of 25 gns were thrown and measured on my modified Lyman M5 beam and the fractional readings smaller than .1 gn were estimates based on where the pointer was between divisions. All readings were obtained by sitting the pan on the balance two or more times looking for repeatability, the balance is sensitive enough to where it will respond to adding a single kernel of Varget and 4 to 5 sticks will move it one full division mark I also timed the RCBS and it averaged the following times. For a 5.0 gn charge 15 seconds, for a 25gn charge 30 seconds, and for a 50 gn charge 35 seconds AVG = average - self explanatory STD DEV - Standard Deviation - measures the dispersion of a dataset relative to its mean. The more spread out the data, the higher the standard deviation. ES- Extreme Spread - The distance between the two most widely separated data points Code:
Hornady Powder Throw IMR4350 TAC Unique HS6 Varget HS4831SC RL10X CFE223 Win 231 AVG 24.64 AVG 25.00 AVG 25.14 Avg 24.98 AVG 25.10 AVG 24.88 AVG 25.07 AVG 24.85 AVG 25.05 STD DEV 0.61 STD DEV 0.02 STD DEV 0.31 StD Dev 0.03 STD DEV 0.10 STD DEV 0.33 STD DEV 0.05 STD DEV 0.48 STD Dev .09 ES 1.6 ES 0.1 ES 1.0 ES 0.1 ES 0.3 ES 1.25 ES 0.20 ES 1.70 ES .3 RCBS Chargemaster 1500 IMR 4350 RL10X CFE223 Win 231 AVG 24.96 AVG 25.0 AVG 25.02 AVG 24.95 STD DEV 0.07 STD DEV 0.05 STD DEV .05 STD DEV .04 ES 0.2 ES 0.2 ES .2 ES .10
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August 1, 2018, 11:22 AM | #22 |
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Thanks for running those tests. The variations you measured with IMR4350 seem similar to my impressions and results of using it with a Uniflow. But I didn't notice Varget being much different than IMR4350, where you achieved much better results with it. What little bit of CFE223 I've used seemed consistent from my Uniflow, where your results showed it to be relatively poor, about the same as IMR4530.
Unique doesn't dispense well from my Uniflow and you saw considerable variation as well. HS-6 dispenses very well for me, and did for you as well. Lastly, I think I get a little better consistency with W231 than what you measured. |
August 1, 2018, 11:32 AM | #23 |
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Technique matters a lot when using a throw, someone with more consistency in their throws could easily get better results. These were thrown with no baffles or weights which I normally use. I dumped each load back into the hopper to ensure a constant powder column weight to some degree. A set of Uncle Nicks powder baffles would have helped tremendously I think.
I only had about a 1/4 lb of CFE223 and could not fill the hopper or it may have done better. The static issue with the Win 231 made it a nightmare both in the pan and the throw, normally it throws better for me also. I had to use a acid brush to get all of the powder out of the pan when emptying it A lot of the extremes occurred when I was cutting a stick and had to force the handle. When I am reloading for real and feel a stick jam or cut I dump that charge back into the hopper and try again, but that would have thrown the test off if I had cherry picked the charges It would be interesting to do some of the tests over with and without using baffles
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August 1, 2018, 01:06 PM | #24 |
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Your ES with the Hornady powder measure and CFE-223 is just that , extreme . I just ran those same test and got very different results . I did as you asked and did 15 with the baffle and 15 with out .
My Redding scale also has the .1gr marks on the scale as well so I guesstimated where the needle was when in between the hash marks . I also used check weights before each test run to calibrate the scale . Here are the weights , I did not feel like writing them all down in the thread so here's a pic . With baffle the ES is .16gr --- with out baffle the ES is .14gr So my test showed regardless of baffle or not CFE 223 in my Hornady powder measure throws to a +/- of LESS THEN .1gr Which is far less then your +/- of .85gr I don't have that bad of numbers when throwing IMR 4064 or 4350 . Are you sure you wrote those down right ? I made the mistake a couple times and wrote 24.02 when I meant to write 24.92gr but caught the mistake .
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August 1, 2018, 01:12 PM | #25 |
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I will repeat the CFE later today. Considering that it is a small flake it should in theory measure almost as well as the TAC. I am slightly dyslexic so I could have screwed up a number when writing them down.
I just did a few more of the 4350 with a baffle in and when I get a stick cutting the numbers jump all over the place, could be your throw is gentler on the stick than mine, or maybe your throwing technique is more consistent I have noticed the Lee Perfect rarely if ever cuts a kernel so all measures are not created equally. If someone does mostly stick that el cheapo Lee would be my choice but with TAC or other ball it likes to leak but there is a cure for that
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