"Geezer tech" - Making a powder chart

Creeper · Apr 1, 2010

Recently, I've noticed on this and other forums that there are more and more target rifle shooters taking loading equipment to the range. Good for you!
I've also noticed that few recreational shooters know what a powder chart is.

For decades (centuries... millennia?), competition, varmint and bench shooters have loaded at the range, and have developed ways to make the process quick, easy and very precise.
When you consider that nearly all competitive benchrest shooters load at the range, and that most all "short" distance accuracy records are held by benchrest shooters... you start to get the idea that loading at the range might be advantageous. You get to adjust your load for the gun, the conditions, the temperature... or just for the he!! of it, to see what happens.
The less stuff you take to the range to reload, the better. The faster you can make changes to a load, the better. A powder chart helps in both those areas.

I'm not going to write about the equipment or the process of precision reloading... I've already done that here. What I am going to write about is how to make a powder measure throw chart.

To begin, I'm going to assume you know the basics of reloading and that you are using a powder appropriate for your cartridge.

Next, I'm going to assume you have a good highly repeatable powder measure with a nice increment range. A Redding BR-30 or something similar (or better) would be a good starting point. The BR-30, if used correctly and consistently can throw charges with no more than 1 tenth of a grain variance.
If your powder measure or your skill at using it is somewhat sketchy... then this isn't going to work very well and you might as well stop reading now, or maybe buy one of them battery powered electric auto measure/scale thingies they make these days.
(Man... that last sentence makes me sound like I'm a 90 year old curmudgeon don't it? )

Oh yeah... the last thing I'm going to assume is that you're an adult who will take responsibility for their own actions and not blame me if you do something stupid.

1. Set up your measure and fill it with the powder you want to chart. Set the measure to it's average setting for the cartridge you'll be loading.
(It's best if you work this for decent size lot of powder, rather than just a 1 lb container... unless your cartridge is small, and you can get a lot of shooting pleasure out of 1 lb of powder)
2. Throw a few charges into a small container, using what ever method you've found to be the most consistent... toss the powder back into the measure.
3. Throw 10 charges into a container and weigh that entire quantity of powder. Write down the weight and the setting indicated on your powder measure.
4. Dump that powder back into the measure and throw another single charge. That charge should weigh exactly 1/10th of the weight of the 10 charges you threw.
In other words, if you threw a 10 charge weight of 323.4 grains, your single charge should weigh 32.3 grains. If it's off by more than your accepted maximum tolerance average, try a different method for operating your measure... if it's within your accepted tolerance, you're set to move on.
5. Now that you know you can throw repeatable charges, we're ready to make our chart. You've probably already figured out what we're going to do next.
6. Back off your measure to the setting that would represent the absolute least weight of powder you'd use for that cartridge/powder/bullet combination.
7. At that setting, repeat items 3. and 4. Record your data for average weight and the measure setting to obtain that weight. Continue to check your throwing skills and accuracy.
8. Increase your measure setting to throw the heaviest charge you'd use for the cartridge/powder/bullet combination. Repeat items 3. and 4.
9. By this point, you should have a high and low range and a rough center for your chart. You can continue to reset your scale to various points and throw charges as outlined in items 3. and 4. How many reference points you choose or feel that you need... is up to you.
10. Using graph paper (or a graphing computer software), you can make an actual chart if you desire. Using the vertical column and horizontal row for your powder measure and powder weight values.
If you don't want to do an actual graph, then a simple equivalent chart or list will be more than adequate.

Here's a short version example:

Setting/charge
24.0..... 29.7 gr.
25.0..... 30.2 gr.
26.0..... 30.7 gr. (median charge weight for XXX grain bullet/XXX OAL)
27.0..... 31.2 gr.
28.0..... 31.8 gr.
29.0..... 32.3 gr.
etc etc etc....
11. You might be surprised to find that powder and measures are fairly consistent. If you're measure setting is '10' and throws 23 grains of powder... it's not uncommon to find that your measure set at 20 throws 46 grains of powder... and so on and so on.
You may also find that for every increment on your measure, the change (for the powder lot you're using) might be highly consistent as well... for example, each increment might represent 0.3 grains.
12. Last... to verify that you're equipment isn't lying to you or that you're not very good at math, load a few rounds at home using you're scale, then produce that same load at the range, with your powder chart and or graph.
If you have a chronograph, then the home-loaded rounds and range-loaded rounds velocities should fall well within your SD... if no chrony, then the home-loaded rounds and range-loaded rounds should all be well within your average group size for a single group.