Home Forums Reloading Big Game Rifles typical variation in powder throw

I've been using a REdding "precision" powder throw for some time.

typical uses are common rifle calibers. 243, 7-08, 308, etc. normal charges in the 40-50 grain range.

when I'm using "stick" powders (4320, 4350, etc) it's not uncommon for two consecutive powder throws to vary as much as 0.7gr per throw when weighed individually.

do yall see that much variation when you check it?

I see far less charge to charge variation when using spherical powders (TAC, Big Game).

just curious if maybe I need to take the whole thing apart and clean it or something.

I've been using a Redding measure for quite a while. I haven't run much IMR4350 through it so I can't say about that one. But if you're getting .7 grain swings throw to throw with the tiny kernels of 4320 there's a problem somewhere. I don't get that much variation with 3031 and 4064 which are Lincoln Logs compared to 4320.

Is your throwing technique consistent?

well, I thought it was.....

I don’t get enough variation with the ball powders to worry about out of my old RCBS Uniflow......but with extruded powders I get more. I know it has been proven to be not necessary, but I still “trickle” in the extruded powder variation. Yes I know, but it makes me feel good to weigh every charge when using “stick” powders.

That is not a bad reason for doing it that way.

I know this is under Big Game, but I have a Harrell's that I use for a 19 Hornet and 1680 powder that varies as much as 2/10th when the temperature changes. I always trickle powder now, no matter what the caliber anymore. Reloading, like shooting is therapeutic for me. Terry

I’m a trickler too, In more ways than one.

Always set mine to throw short, then trickle to what I want.

Titegroup for pistols, I weigh about 1 in ten since I’m in the middle of start and max.

What kind of scale are you using to weigh the charges? How accurate and consistent is it?

Billy Goat,

That amount of variation is pretty typical for stick powders, especially larger-granule stick powders like IMR4350, even in the best measures.

thanks John, and for the other responses.

while I love reloading, I cant confess to being a "trickler". in fact, I don't own one. When I first started reloading, my "trickler" was a teaspoon stolen from my moms kitchen. I still have the spoon at my reloading bench. (don't tell mom) =P

Once I get the powder throw dialed in, I'll "throw" 50, and then just do a visual inspection to make sure:

1. all cases have powder and
2. the powder level looks close from case to case.

I used to use an RCBS Uniflow. I spent the $ on the Redding in an effort to get more consistent powder charges long long ago, and didn't realize until recently that I haven't been getting it. =/

That said, it hasn't caused a major accuracy issue thus far. It does make me leery about using it on the upper end of the load range, through!!



I used to use a RCBS beam scale for measuring weights, but have absolutely fallen in love with a very simple Hornady electronic scale. it is stupid simple to use, and very consistent. Love that thing.

I was taught to trickle charges up to weight when I started reloading in the early 70's and have done so ever since. I have been using a Redding measure for some time now having previously had an RCBS Uniflow, I don't feel that the Redding works any differently than the RCBS. As for scales I have used many different balance beam and electronic models, my preference is the Ohaus 10-10. With the Redding/Ohaus combination I can load accurate ammunition for hunting rifles. Like the OP I see variation from throw to throw from the Redding measure, but since I trickle to weight it doesn't concern me.

A few years ago, I did an article for Varmint Hunter on scales and powder measures. Some of the test results were a bit surprising.

The Lyman digital scale was a "houseplant". It really required stable temperature conditions for satisfactory results. The Hornady balance scale was very robust and oblivious to temperature changes, disassembly/reassembly, etc.

The humble Lee Perfect Powder Measure beat the much more expensive Hornady measure.

Lest you should worry, all the devices tested were satisfactory or better.

With 2520 ball powder, the random error in the Lee Perfect Powder Measure was better than I could measure. The Hornady balance scale turned in a standard deviation of .043 grains, so 99.7% of measurements would be within plus or minus .129 grains.

With H4831SC, the standard deviation of the measurement error was .1 grain for the Lee, and .14 grain in the Hornady Lock N Load. So 99.7% of measurements would fall within plus or minus .3 grains or .42 grains respectively.

That should give you an idea of what is "normal".

These errors are entirely inconsequential unless you a shooting a remarkably fine rifle at very long range. Error does not add linearly, and there are other sources of error in the system that swamp out the effect of charge weight variation. For practically all applications, individually weighing each charge has no detectable effect vs. using a good quality powder measure.

I see what you did there.

Another factor is that a large amount of powder-weight variation (say +/- .5 grain, or even more) often doesn't make any practical difference in accuracy, except at ranges beyond where most shooters shoot. In HATCHER'S NOTEBOOK, General Hatcher states (as I recall) that .30-06 National Match ammo often varied =/- 1.5 grains in powder weight, yet shot very well in accurate rifles out to 600 yards.

The reason generally given for this sort of thing is that the most accurate powder charge for a certain bullet tends to hit the barrel node, where the muzzle is in a reasonably stationary position when the bullet exits the muzzle. A little variation in muzzle velocity of, say, .0136% (which would be the approximate variation of a .30-06 powder charge that varies .75 grains from average)in a reasonably stiff barrel wouldn't make a significant difference at 600 yards, especially when shooting iron sights.

A lot of handloaders assume that "zero" variation in powder charge automatically results in finer accuracy. It doesn't, especially at the distance most handloaders shoot--which is often 100 yards max. Other factors are far more important than a variation in charge weight of a few 10ths of a grain. But many handloaders (often older, but not always) waste a bunch of time "perfecting" every powder charge to within a gnat's weight. (I have no idea what gnat weighs, but it ain't much.)

It's far more productive to adjust other factors, both in the rifle and handloading.

Consistently better "groups" may be more directly proportional to the amount of coffee you consumed, rather than the accuracy of your "thrower".

I weigh each charge so there is no variation...because I can.

I weigh each charge too, especially when using powders like IMR4350. None of my rifles complain (in the accuracy dept.), so I keep doing it...

Yep, besides that my uniflow "cuts" longer stuff and then stumbles and pucks so I just avoid all that and it makes for a much more enjoyable loading session.

Weighing each charge certainly does no harm, and if people want to do it, I make no objection.

However, consider the following bit of math:

Random variation adds by the square root of the sum of the squares, not linearly. That's a mouthful, and may not mean much to most folks. But it has profound implications for shooters.

The 223 has a small case and is therefore more sensitive to powder variation than say the 270 or 30-06. In round numbers, a grain of powder is 100 FPS with 55 grain bullets. Typical commercial ammo has about a 25 FPS standard deviation.

So, for example, assume that you have a lab grade scale capable of measuring to the milligram. Also assume that your ammo is a bit better than most commercial stuff, and has a standard deviation of 20 FPS. Based on my experience, that's in the ballpark.

Now assume that for the sake of convenience, you want to start using the inexpensive Lee Perfect Powder Measure, and that you are using ball powder. In that case, I have measured the standard deviation of the powder measure, and it is right around .04 grains. .04 grains is about 100 FPS X .04 = 4 FPS standard deviation in muzzle velocity.

Now do the sum of the squares math: (20^2 + 4^2)^.5 = (400 +16)^.5 = 20.39 FPS.

So in that case, moving from an extremely good lab scale to an inexpensive powder measure increases that standard deviation of muzzle velocity from 20 FPS to 20.39 FPS. You'd have to shoot a really, really large sample to even show that the change had happened.

I also tested the variability of H4831SC. Of course, that is not a suitable powder for the 223, but I expect that Varget is at least close in measurement variation. In that case, the standard deviation of the powder charge is .1 grain. So the standard deviation of the muzzle velocity due to powder charge is .1 x 100 FPS = 10 FPS. Doing the math, (20^2 + 10^2)^.5 = 22.36 FPS, from a process that was formerly 20 FPS.

The day I did that math, I quit individually hand weighing charges.

The result of the math is:

1. If one source of variation is much larger (say 2X) than the others, then it alone almost completely determines total variation.

2. You will never succeed in improving a process by working on several of the weak variables. You have to find the strong contributors, and work on those. In most practical situations, the main source of variation is the shooter. So there is more truth than poetry in the coffee comment.

I've used two measures but not that one.

Variation with spherical powders, both rifle and handgun, is essentially nil. I get no more variation in weighed consecutive charges than I do in re-weighing the same charge multiple times. The only thing that has caused variation with my current measure is how much powder is in the hopper. It throws heavier, not lighter, as the hopper empties. I think this is a matter of tapping the handle also settling the powder more densely in the measure. Once some max has been hit, keeping the hopper roughly the same level by adding a little more at a time rather than waiting and doing a large refill resolves the problem

Variation with long cylindrical powders is pretty bad, enough to blow up a gun. It varies both high and low. I only ever use the measure now to load the pan for my scale with a near but short charge, then trickle up to weight.

Flake powders are worse. The absolute variation is less but the total charge is very much less causing a higher percentage deviation. An example ... I was loading 10 grains of Blue Dot weighing thrown charges. Variation was from around 8 to over 13 grains. That can blow your damned gun up and take your head off with it.

Tom