Cleaning: Part 1 = When to clean: Precision Window and Time
Updated: Nov 12
As a Benchrest competitor, cleaning the rifle is a mandatory chore. I do not know anyone who actually enjoys cleaning their rifle, but I also do not know anybody who despises it either. Cleaning the rifle is simply a job that has to be done if you want to protect and preserve the looks and, more importantly, the precision/accuracy of the rifle.
A very popular question about cleaning is; “When should I clean?” That is a great question. Unfortunately there is not a simple answer. When you should clean depends on a few main questions; where is the barrel in the precision window, when will you be shooting again, and how easy do you want the cleaning to be?
The answers to these questions are subjective to the shooter and the barrel. Meaning, when one person decides to clean may not apply to another person. Here is the process to figure out when you should clean.
Simply stated, the Precision Window is the range of shots (window) where the barrel shoots the tightest (precision). As the diagram shows, most barrels do not start out in the precision window. It usually takes a shot (or two, three, etc) to get it there. Those shots are called fouling shots. Others say they are settling the barrel. Regardless of terminology, competitors know exactly how many rounds to fire to get their barrel into the precision window.
It is an easy process to determine the beginning of the window for a particular barrel. Go to the range with a tuned, clean barrel and some loaded rounds. Using a solid rest (I am also a believer in using wind flags, but that is for another blog) fire a round at a small aiming point. Without changing your sights (meaning - do not care where the bullet impacts as long as it is on paper) fire another round. If that two shot group is acceptable, then do not worry about where the precision window starts. Just shoot and have fun!!! However, if you want to squeeze the highest amount of precision out of the rifle, you may need to keep shooting. Repeat the process until your group tightens up, that is the beginning of the precision window. A safe standard for most custom barrels is two fouling shots. However, I do have to take three fouling shots on one of my “out of the box” hunting rifles before I experience the highest precision with that rifle.
Here is a good example of how to determine the precision window. The first, clean bore, bullet impacted roughly .75" high and slightly to the right of where the 2nd and 3rd shot group forms in a fouled barrel. That's all I needed to know. For this particular barrel, I can start to trust the second shot. Target was shot at 100 yds with a Krieger barrel chambered in 26 Macho.
The best precision, and therefore accuracy, will be when the barrel is in the precision window. This is when you want to be tuning, practicing, on the record target or hunting for that trophy animal.
Each barrel has a different “breaking point”, the point in which precision suffers due to a barrel being too dirty. This is the end of the precision window. The term "point" is a misleading. Very seldom is the loss of precision sudden as in what the word describes. Rather this loss is gradual. Cleaning should be done before the breaking point. (FYI: The Krieger barrel mentioned above has a precision window that starts at the 2nd shot and goes through around 30) The risks of going past the "breaking point" greatly outweigh the reward of not cleaning. In competition, going past the window could move you down the list pretty quickly. In hunting situations, you might not even notice it to start with. However, the farther past the window you go, the lower the level of precision. A certain double lung hit now may turn into a gut shot. Many shooters have blamed their scope or load being bad, when all they had to do was clean their barrel to bring the precision back to life.
I believe there may be a correlation between bore diameter and the precision window. My theory is the bigger the bore diameter the bigger the window. Stated another way, you may be able to shoot your 30 cal. rifle longer between cleanings than your .22 cal. rifle. Regardless if my theory is correct, the target will tell when it is time to clean.
Many of my 30 cal., custom, competition barrels can go well over fifty rounds before precision deteriorates. Those custom barrels have a large window. Compare that to the twelve rounds in one of my factory barrels, and you can see not all rifle barrels need to be cleaned at the same point. Find the precision window of your rifle barrel, and clean before the breaking point.
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When will you Shoot Again?
Another main factor you need to consider is; when are you going to shoot that rifle again? Smokeless powder is corrosive, especially when it absorbs water, such as humidity from the air. Black powder is even more destructive in the smoke poles. The longer the fouling is left in the barrel, the greater the chances of corrosion. This is a precision killer, and may ruin the barrel.
Regardless of where the barrel is at in the precision window, if you are not going to shoot again for an extended period of time, clean it. Most hunters (minus a few varmint hunters) will not reach the end of the precision window during a hunting season. Therefore, time will be the determining factor on whether they should clean or not. My rule for hunting rifles is four weeks; a competition barrel is two weeks.
How "Hard" do you Want the Cleaning to be?
An additional piece of the time puzzle is how much work do you want to do? Think of your barrel like the dishes after a big meal. The longer they sit, the harder it is to get them clean. Some competitors will clean after every relay. This may have as much to do with the ease of cleaning as the precision window.
One last item to add to the "pool of knowledge"; each barrel's cleaning personality may change as the round count increases. Most often, the barrel will get more difficult to clean and the precision window will shrink. This is something to keep an eye on depending on the level of precision desired.
Based on your own experience and barrels, you can now decipher where the precision window starts and ends, as well as determine how long you are willing to go between cleanings. In part II of this blog, I will help you establish a cleaning process. Until next time, enjoy the experience.