December 14, 2021
Have you ever eaten something that didn’t agree with you? Like heartburn telling you you shouldn’t have eaten those habanero peppers. The body’s response will help you make better decisions in the future, and rifle barrels will communicate with you in much the same way—signs that tell you what it does and doesn’t like.
I gathered this information from years of experience, discussions with other competitors at matches, shooting seminars and road trips with accomplished shooters. Many competitive marksmen including Hall of Fame members Mike Bigelow, Randy Robinett, Jack Neary and Speedy Gonzales have been gracious enough to share much of this information.
Time to Clean
Every barrel has a precision window—the number of shots, between cleanings, where the groups are the tightest. This window is largely dictated by the amount of fouling in the barrel. What differs among barrels is the starting point and width of that window.
The vast majority of tuned rifles will shoot better with some fouling. The process of shooting rounds to enter the precision window is called fouling the barrel. Starting with a clean barrel, the tube will tell you it has entered its precision window when the groups quickly tighten up.
Precision will start to decline once the barrel exits the window. For most barrels, this initial increase in group size is very slight. However, the farther from the window the barrel gets, the louder it will tell you it is time to clean.
Telltale Group Shapes
Group shape is the main tip-off as to what might be going on with your bore. Here are six common group shapes and what they could mean.
A vertical group is typically the barrel’s way of asking for an increase in powder charge.
A horizontal group might mean the shooter missed changes in the wind. However, horizontal stringing could also be the barrel saying there is a seating depth issue and/or it wants a slight increase in powder to drive through the conditions better.
A diagonal group might be your barrel’s way of requesting an adjustment in neck tension.
Double grouping (3/2 or 4/1 pattern) is an indication that your load is getting too hot. Pressure signs may also accompany these groups.
5. Train Wreck
The dreadful train wreck: No two bullets are close to touching. Lots of things could be wrong. When this happens, assuming there are no equipment malfunctions or horrendous shooting conditions, major changes are needed to powder charge and/or seating depth. Train wrecks could also indicate there is a wrong bullet/powder or bullet/twist rate combination.
The round group indicates the barrel likes what it is shooting. Keep in mind, the size of this cluster is relative. A custom rifle’s circular cluster should be smaller than a group from a factory hunting rifle. However, the overall round shape will remain the same in rifles that are in tune with their loads.
Time to Retire the Barrel
Barrels are similar to car tires. They eventually wear out and need to be replaced. Just like car tires, not all barrels wear out at the same rate. Do not fret. When you listen, the barrel will give some signs it is getting tired.
Toward the end of its life, the barrel will start shooting increasingly larger groups. Initially, these slightly bigger groups are hard to decipher. Did I miss a condition? Is it time to clean? Is the load requirement changing for some reason? Or is the barrel saying it is close to being used up?
A tiring barrel will also produce some signs that are easier to interpret. Cleaning patches will gradually start becoming darker blue due to the barrel scraping off more copper. Another sure sign is the increasing amount of time and effort it takes to get the barrel clean. When added together, these signs give a good indication the barrel is nearing the end.
Sometimes these indications are subtle—small changes in group size or slight changes of color on the cleaning patches. Sometimes it’s obvious—sizes and shapes of groups when you’re in the precision window. Regardless, the barrel can tell you what is going on if you pay attention.