Why:
If you have ever used a tuning fork, you will know that it will only resonate when struck. If you've ever used a tuning fork incorrectly, you will know that you can change how it sounds by hitting it on different types of objects, or by changing how much force you hit it with. The sound you are hearing in all of these instances is the tines of the fork moving at different frequencies. The pressure of impact on the tines caused the change in frequency. A more forceful hit makes the sound last longer; hitting on a softer surface mutes the tone, so it doesn't sound as clear. The more forceful hits have more pressure, and the softer surfaces have a different wave of pressure.
The same thing is happening to your barrel when you fire a round. The powder burning in the case builds pressure. This pressure is what drives the bullet out of the chamber, down the barrel, and ultimately to your target. Different charges of powder will result in different pressures, which changes how your barrel vibrates. Different barrels, even from the same manufacturer will react differently to the same powder charge.
What You'll Need to Look For:
- Brass: You need to use brass in the same condition for the most accurate setup. If all you are going to do is shoot new brass, then that is what you need to use. If you are going to use all once-fired brass, then you will have to get once-fired brass of the same headstamp, preferably fired out of the same rifle. Each step away from new brass will decrease your accuracy slightly, but there are other methods to compensate (neck-sizing, concentricity gauges, etc.). The key here is get your brass as uniform as you can.
- Primers: Primers should be ideally of the same lot, from the same manufacturer. The beginning pressure that primers exert and the amount of spark they give off will vary slightly between lot to lot, and could vary significantly between manufacturers. A different lot of primers could cause a slightly different point of impact than previous examples.
- Powder: Like primers, powder can vary between lots. Ideally, you should use powder of the same lot for as many rounds as you are loading.
- Get 100 cases sized and primed. How you do this is not important in the focus of this article. The key thing to remember is it needs to be consistent with how you plan to load your ammunition after you have found your most accurate powder charge.
- Using the reloading manual of your choice, find the minimum and maximum powder charges. This will be your powder range. Divide your range into 10 separate charges. These will be what you charge with in your next step.
For example: If your minimum charge is 25.5 grains of powder, and your maximum charge is 30 grains of powder, your charges will look like this:
- 25.5gr
- 26.0gr
- 26.5gr
- 27.0gr
- 27.5gr
- 28.0gr
- 28.5gr
- 29.0gr
- 29.5gr
- 30.0gr
- Charge 10 cases with each charge from the last step.
- Seat and crimp your bullet as you normally would.
- Clearly label your rounds with as much information as you can muster. Keep each set of rounds separated from the others, so there will be less chance of confusion.
Your next step will be to do the most fun part, shooting your loaded ammo! You will want to take 10 targets and head to the range. Set your targets out at the distance you have zeroed your rifle. Single-load your rifle and fire ten rounds at your first target. Don't worry about adjusting your sights. There may be a small amount of difference from where you zeroed at to where it is impacting now. Mark on the target the load that you fired. Inspect each piece of brass for signs of high pressure.
Continue shooting 10 rounds at a different target, marking it, and inspecting the brass until you run out of ammo. Compare the targets. You should notice that two or three targets are giving much better groups than the rest. These are the sweet spot for your rifle. This load will perform adequately for your rifle. If you want to, you can take the ammo back to your press and start again.
EXAMPLE:
Let's say that using our example from the previous range that 28.0 and 28.5 and 29.0 gave you the tightest groups, with 28.5 being the tightest. In this instance, I would repeat the above process with the charges by 0.1gr increments, and see which one of these is the best.
FREQUENT ISSUES:
Occasionally, the powder you chose just doesn't seem to work well. Unfortunately, this just means that you need to go back to the drawing board and start again with a different powder.