Conditions to Tune
Updated: Jan 12
Tuning a rifle is a major part of the precision game. Load development is a systematic process where decisions are made based on what the groups tell us. There are many pieces of the tuning puzzle that can affect the group shape. Bullet, type and amount of powder, seating depth, and neck tension are all key components.
An often overlooked, yet vital, piece are the conditions in which the tuning is done. Regularly, conditions have a bigger influence on the group shape than the components used. To make correct tuning decisions, the shooter has to know if the groups were caused by the components or by the conditions.
Conditions NOT to Tune In
Unreliable data is worse than no data at all. Let us start with conditions that may produce deceptive data and therefore are not good to test loads in.
First up are days with heavy mirage. While looking through your sights, mirage will make the target blurry and seem to dance around. This optical illusion is caused by the refraction of light through layers of air with different temperatures. Mirage usually occurs at times when there is considerable sunshine. Very few shooters can get reliable tuning data while shooting in this condition.
The second worst condition to do load development in is when there is no wind. This condition routinely occurs in the early morning and late afternoon. Mistakenly, this is when the majority of people want to test loads. True, windless days can produce some great groups. The groups that lead a person to believe their quest for the perfect load is over.
On the other hand, these days may also produce some shots that leave us wondering; “How did that happen?” On calm days, your guess is as good as mine at predicting if you will shoot a wallet group or a train wreck.
Benchrest shooters believe these non-wind times are when the gremlins come out. “Gremlins” are to be blamed for the unexplained flyers that wreck the group. Unexplained shots are not what we are after while developing a load. Bottomline, days with heavy mirage and windless days produce unreliable data and therefore not good conditions to tune in.
Mistakenly, many shooters want to test loads or tune their rifles when there is no wind, On days when the tails are hanging, go fishing.
FAVORABLE Conditions to Tune In
When testing different components many people shoot three to five shot groups. These groups are the foundation for future adjustments. In order to trust the data, the groups need to be shot in the correct conditions.
This starts with little to no mirage. No mirage is best, though some mirage is fine. Mirage will act as another wind indicator and give the shooter a baseline for the condition they want to shoot in. The data on target can be trusted as long as the target is clear and the shots are fired when the light mirage is running in the same direction.
Clouds help to minimize mirage. When you are looking at the weather forecast to find a time to tune, pay attention to the predicted cloud cover.
The wind speed is another factor to pay attention to on the weather forecast. Time periods where there is a steady five(ish) mile per hour wind are best. These light, steady winds seem to “even out” the gremlins and allow for accurate data. Switchy or strong winds can simply produce too much movement in the bullet to trust the data.
The temperature we tune in is also an important aspect of the conditions. The closer the temperature is to what we will be competing and/or hunting in, the more reliable the data. For hunters, twenty degrees is usually a safe margin. Any deviance more than that and the data could be unreliable. With that being said, some powders are more temperature sensitive than others. A little research and you will know how critical of a factor this is for you.
This information may make it seem impossible to find a time to tune. Remember, the whole day does not have to be favorable. Tuning can usually be accomplished in a short amount of time. Look for a few hours in the forecast where there will be ample clouds, low/steady wind, and a temperature decently close to what you will be competing/hunting in.
When the tuning starts, Benchrest shooters rely on mirage boards and wind flags to give them a sense of what the conditions are doing. Long range and PRS competitors use mirage and nature’s clues for their data. Virtually all competitive rifle shooters use some sort of wind indicator to ensure they fire in the same condition. Simply put, the data on the target will be more reliable when using wind indicators.
Please do not get me wrong; any day is a good day to go shooting. The days that are not good for tuning can be great practice days. However, tuning and practicing are not the same. The process of load development requires you to make decisions based on reliable data. Better tuning decisions can be made when the groups are shot in the correct conditions. Until next time, enjoy the experience.