How Important Is Consistent Powder Charge

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Ralph124c41

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Most re-loaders put great stock in the precise metering of powder, believing that consistent powder charges deliver consistent groups. Recently, preliminary measurements cause me to question this belief.

Having purchased a more accurate scale recently (Sartorius Entris64-1S) I was curious about how consistent the charges were from my powder measure (Redding Competition 10X Pistol). I found that most of the charges thrown were within ±.02 grains of the mean.

I measured the muzzle velocity (a proxy for point of impact, all other things being equal) for each of 150 rounds having weighed each carefully before hand.

When I used Excel to correlate powder charge weight against muzzle velocity I found that it was about .3. This is hardly a close correlation. I would have expect something around .7 to .99.

I wonder if anyone else has performed similar measurement?
 
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Some of us are much fussier than we need to be. Some of us dump 120 grains of powder into a 470 Nitro case and still weigh to +/- .1 grain. Probably excessive but it's a harmless obsession.
 
.3 what? The post is too vague on scope. Loading rifle for LR precision is different than loading pistol even for a match. Many of us fine tune down to the tenth of a grain and see meaningful results in our rifles at distance. In a pistol you're wasting your time with such anal probing. If you're a pistol shooter you probably don't need to weigh each charge by hand with a trickler. If you're a rifle shooter trying to maximize LR accuracy you won't be too impressed with charges dumped out of a measure.
 
I know I am way too concerned about precision of powder charge, but it is one of the easiest variables to control, so I do it anyway.
 
IMO the faster the powder you are using the trickier it becomes.I use shotgun type powders and even 0.1Gr makes the difference with some cartridges.
On other hand when I reloaded 8x57 with H4350 +/- 0.3Gr didn't really matter.
 
A .3 correlation is pretty weak, as you said. If I remember my fancy book learnin' over three advanced stats courses in university that's practically no level of correlation at all. If you're ±.02 grains of the mean I think you're probably doing far better than the average reloader who is using a electronic dispenser and typically getting ±.1 grain or those using the volumetric throwers, which I've never had any great love for, and getting something similar.

At any rate, if your data is correct and you analyzed properly, I think you answered your own question...at least with that powder at the hundredths of grain of powder level. I wouldn't draw similar conclusions about other powder obviously.
 
pretty sure that weighting to the kernel with pistol loads is totally useless....
I just use the dillon powder measure and it produces ammo that shoots better than me, so I could care less.

for match 308 ammo I like to weight to +-.02 grains using the gempro right now, but I might or might not get a fx120i with autotrickler in the future.

Honestly, neck tension probably has more impact that the .1 or .02 thing.

But hey, the entris is a 2000 $ scale that weights to +-.002 grains dude, wtf for pistol? It can weight a fifth of a kernel, that's excessive.
Unless you want to win the world record for 308 shooting, I don't see the point with the .002 scale
 
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Weighing to the hundredth of a grain won't add measurable benefit to bullet velocity consistency, especially in pistol loads. Try weighing the bullets themselves and my guess is that you'll find multiple grains of weight difference - a factor that will hide any trends from powder load changes. Further, at pistol distances I'd like to see the person who can hold so well to make a few fps matter in terms of their groups.

In some rifle loads, 0.5 grains of additional powder results in about 50 fps change in muzzle velocity. Assuming a linear relationship in powder/mv, you can see how negligible +/- 0.01 grains would be in terms of mv. As mentioned above - there are many other factors that are more significant.
 
I'd say it comes down to how you chose the load your using.

A fellow I compete with went through this experience earlier this summer. Weighing to the kernel seems far too much work for no measurable gain.
 
You can claim all sorts of things by loading to less than a tenth of a grain will make a consistent difference in cases from 223 Remington to the huge magnums. I think it is mostly a feel good issue in the end.

The theory seems to be fine and should work if everything else were absolutely consistent as well. Powder lots are notoriously inconsistent as are primers and not just from lot to lot. Same goes for cartridge cases and the bullets themselves. Then of course there is altitude/temperature/mirage/sunlight/rain/clouds and Voo Doo.

It isn't rocket science and it isn't precise by any means. At least not to any controllable point other than on a + or - acceptable variance level. The only thing we have any real control over is the condition of the firearm and if we build it ourselves, the tolerance standard it has been built to. Then, we have to find a press that has a mandrel that is consistent with the axis of the seated die and a die set that is consistent as well. Far to little attention is placed on these variables and otherwise anal reloaders don't even bother to check out their presses/dies for consistency and whether or not they are all true to the axis of the mandrel when assembled.

Let us not forget neck tension, seating depth, brinnell hardness of the jackets and let us not forget, the consistency of the lead cores.

But if a tenth or less of a grain makes you feel more comfortable and confident it has accomplished a great deal and relieved a bit of accuracy killing stress.

This is all just IMHO of course.
 
Don't forgot about the measurement error in your primary outcome measure - velocity. Different Chrono's have different measuring errors.

Your question is a good one, and your interest is excellent.

Welcome to the science/witchcraft of reloading.
 
Powder charge consistency only starts to matter greatly when your trying to shoot past 600yrds, an example with H4350 each stick of powder can attribute to 8-12fps. When you start shooting at distance for consistancy it matters. For 95% the hundreth of a gn doesnt matter. That being said if the other variables that affect pressure are not exact you stand to gain no benifit from super consistant charge weights. Anneal, turn, neck tension, then charge weights..
 
While it may not be the most important factor in shooting accurately, it is one of the easier ones to control, and imo worthwhile putting
in the effort into getting it at least a tenth of a grain of a known load. Most scales are easily this accurate, why anyone would lower their
standards beyond what has been the benchmark lowest unit of measure for the last 60+ years is beyond me.
 
You didn't say what caliber you are loading and what you are shooting it out of and what distance you are shooting.

a 1% difference in muzzle velocity for a small caliber pistol at 20m is not much of a difference for grouping but quite a big difference for a large caliber rifle at 800m or beyond.
 
Probably the most common handloading accuracy question there is. There never has been and never will be agreement.

Some claim that +/- 0.010 grs is required because every single factor matters. Others like me load to +/- 0.100 grs, don't clean primer pockets and am satisfied.
 
My approach is to make the most uniform ammunition that I can within the limits of the equipment and the components that I use. I don't bother with charges below .20 grains, because my 505 doesn't have the precision to consistently weigh those charges, so I round off to the nearest .20 grs. More important than the ability to weigh increments smaller than a tenth of a grain, is how I setup the scale. The usual practice is to zero the scale to zero. The trouble here is that the farther you move the counterweight from zero, towards the charge weight, the greater the error becomes. So using check weights, I zero the scale to the charge weight I intend to use.

Of course powder charges are but one measure to be concerned with. We also need to know that our bullets and powder volumes fall within tight tolerances. Consistent case length, neck concentricity, primer seating depth and pressure, and bullet pull weight all come into the accuracy equation. Some of the steps in my reloading process make unmeasurable differences, but when combined with a number of other steps, the overall result is ammunition that is more consistent, resulting in lower extreme velocity spreads, and better accuracy. Sometimes it just makes me feel better.

When you resize a cartridge case, an interesting experiment is to first check the neck runout from a fired case, then from a resized case, then from a cartridge with a seated bullet, and finally from a cartridge case with a seated and crimped bullet. At what point in the loading process does concentricity take a dump, and what can be done about it, if it does. Something as simple as placing a rubber "O" ring between the resizing and seating stem locknuts and the die, and between the lockring and the press results in an improvement, as can replacing the shell holder retainer with an "O" ring.
 
Excellent suggestion regarding the influence of projectile weight on muzzle velocity. I will do a trial run of 50 rounds to get a sense of the bullet weight variation and then how that correlates with muzzle velocity. Many thanks. Ralph1s4c41.
 
A consistent powder charge is important for accuracy.

That said, it's a combination of parameters that begets a good load, these are:

Low variance of case volume
Concentricity of the loaded round
Consistent neck tension
Primers seated to a consistent depth
Consistent powder charges +/0 0.02 grains

Do all that and you load still might not perform, the key is finding OCW (OCW will be one that has all of the deterrent chemicals consumed at peak pressure 'optimum burn') and the charge weight produce a velocity that is on a barrel node.

Sketchy velocity readings can be resolved using a LabRadar or Magneto-Speed, barrel nodes and optimum burn can be found using QuickLoad.
 
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