Check weights

[cdoc42]

zxcvbob, have you ever weighed those scoops from the dipper just to see if here is any variation of significance? Those little granules (assuming it's not ball powder) of stick powder don't sit exactly the same place with each scoop, so bridges will alter the weight even though the scoop seems level at the top. As well, what appears to be level at the top may not be, given the absence of a meniscus as seen with a liquid. I also find it rare that any Lyman scoop (in a set of 14) by itself will give me the desired weight. I often use 2 (e.g., #3 and #12) to get close to my target weight.

As such, I use Lyman scoops to get close to my designated weight, then trickle the remainder to goal. Maybe, if I really take care (and that takes more time) I can get a scoop filled with my target weight of 56.0 grains of H4831 one or 2 times out of 10. Now I will say, more often than not, I need only trickle from 55.7 or so to get to 56.0. At the same time, I can easily find 3 of 10 to be 56.5 or more as well. So I weigh because I'm more concerned with over- than under charges.

[zxcvbob]

I don't use scoops yet, I use either a CH or Hornady powder measure (I have both.) But I'm thinking about making scoops for my favorite loads, so I can quickly make up a box of them when the press and powder measures are setup for something else.

They will be as consistent as my technique is -- which remains to be seen

[Bart B.]

I don't think it matters if your scale is off a few tenths grain, either beam or digital, from some exact laboratory standard. Most important is if its weight is the same number each time some reference is used.

You can use a bullet of some weight as a "check weight" such as a 50-gr. 22 caliber, or a 70-gr. 24 caliber one. Heavier bullets for checking scales for 50 caliber BMG round's powder charges. Doesn't matter if that 22 caliber one weighs 49.802746 grains on a environmentally stable multi-thousand dollar laboratory precision balance.

The next lot of powder you use for your favorite load with a given cartridge will have different peak pressures and muzzle velocities using the exact same charge weight of it. Reloading ammo is not an exact science. Very close is all one should expect and plenty good enough even for benchrest record accuracy.

Sierra Bullets does not work up charge weights for each lot of powder (nor primers, bullets and cases) used to test their stuff for accuracy. They use the same recipie every time and meter (not weigh) their powder charges. They shoot their best match bullets under 1/4 MOA at 200 yards.

[wogpotter]

As such, I use Lyman scoops to get close to my designated weight, then trickle the remainder to goal.

This is what I do for a short or test run. IMO its the single best combination of speed, accuracy & repeatability. My scoops are Lee though.

[cdoc42]

Barb B said: I don't think it matters if your scale is off a few tenths grain, either beam or digital, from some exact laboratory standard. Most important is if its weight is the same number each time some reference is used.

The chemists among us can better clarify this, but I see 2 issues here.

1) The sensitivity of a balance beam or digital scale is the key to precision, which translates for us into accuracy of the weighed product. Your device may be more precise at a higher weight, i.e., 50-60 gr, but less so at 3.5-4.0gr. So a set of known, and accurate, weights to calibrate your device is important. That way you can be sure of, or at least more comfortable with, the result you obtain as you work up a load. If your pet load is less than 1 MOA with a 55.5gr load of H- or IMR- whatever, you know you worked this up, maybe, in 0.5gr increments.
If you feel 55.3 on a low side or 55.8 on a high side is o.k., that depends on whether your group stays at less than 1 MOA with that spread.

2) It's my impression that the powder companies produce their lot numbers based on pressure tests, to be certain that we don't blow up our firearms by accident. That said, your pet load at 55.5gr with Lot ABC may not produce that 1-MOA with Lot DEF. They are both safe at 55.5 gr but you may be surprised that your last trip to the range is no longer as accurate with this new lot of powder. You may need to experiment to find that you need 55.3 or 55.8gr.

Now these threads have discussed whether the need to be accurate should simply be confined to the bench rest crowd, and most of us are probably not in that group. But if you're going to go through the exercise and expense of reloading your own, you just don't want to throw them together to get a group that's satisfactory enough to knock a deer down. If that's your philosophy, you can do that with factory rounds.

All that being said, you want to reduce the variables down to just you, your trigger finger and breath control. Having a set of standardized check weights is a move in that direction.

[Brian Pfleuger]

Trouble is, the variables may not be what you think they are.

As it turns out, volume matters more than weight when it comes to powder or at least some experiments have shown that to be true. In any case, it is well known that EXACT charge weights are definitely NOT important. Very few competitive shooters weigh their charges.

We also know that uber-precise check weights are way outside of what any reloader needs to verify their scale, in any case. For one thing, almost all scales come with one or two check weights. For another thing, absolute weights are irrelevant, repeatability is what matters. Getting the same number for the same weight matters a LOT more than getting the "true to the laws of physics" correct weight.

[BuckRub]

Lets say you get your check weights and check your 9 MM charges. They're slightly off- do you adjust for this to make it perfect ?
Then you load your 308s and off again, better readjust and so on and so on.
Like Bart said, doesn't matter as long as it same over and over. Get your bullets hitting perfect and whatever it is it is. Now do same for other guns, whatever it is to make it shoot a ragged hole. Don't worry about your scales as long as its repeatable. Let your bullets make that ragged he to tell you its right.

[cdoc42]

I can understand that volume is important, and obviously bench rest shooters get away without worrying about precise tenths of a grain changes. But then why do the manuals, for as long as I've been reloading, present us with data that show a change in velocity with changes in weight, which essentially forces us to concentrate on fractions of weight change?

[Bart B.]

I don't think exact charge weights force anyone to be exact to lab standards. People choose to do so freely on their own. Humans interpret what they read; they're all different and each one thinks differently after reading something. But the data's the same for everyone.

Those exact weights for charges are best used to create a graph showing how much velocity change there'll be for a given charge weight change. But that will only be an approximation because each lot of powder will be slightly different. And it only applies to the specific lots of powder, primer as well as specific case, bore and ammo assembly the data was derived from.

Ammunition creation is not an exact science. There's only one exact science; mathematics. But some computer geeks claim:

2 + 2 = 3.999999999999999999999999999999999999999999999999999999

because that's what their digital systems come up with.

Shady accountants keeping (cooking?) the books for some folks take the approach that 2 + 2 = whatever they want it to be.

[Greg Mercurio]

This is a really interesting thread, but way over the top as regards real life. Unless you are using some POS scale, the accuracy of the scale is more than adequate for reloading purposes. The manufacturer provided check weights are more than close enough to calibrate with and your ability to meter charges to more than 1 place accuracy is moot.

For digital scales: If you don't believe me try trickling ball powder into the pan until the number changes at the 10ths. Then trickle some more slowly until it changes again. Note how many tiny granules it took. That's the uncertainty in your charge. Is it significant? Not really.

If you didn't get check weights with your scale, get a set. If you are using a beam scale, still get a set. Peace of mind is important in reloading.

[Gster]

I use a digital scale for all my loading and every once in awhile I'll set a check weight on it if it's varying a tenth or so. I made my own check weights from various wire nuts that I weighed on my Lee safety scale. I wrote the weight on them with a fine point sharpie. They work great.