When choosing a cartridge, most people are far more concerned about barrel life than they have any right to be. Most shooters fall into two categories; Those who will never shoot out a barrel and those who treat barrels like tires and expect to replace them periodically. Still, different cartridges do have wildly different average barrel life and trying to troubleshoot a barrel that is shot out is a waste of time and money. As such, it’s important to know when to be watching for the signs that your barrel has given up the ghost. This raises the question, how long do barrels last?
What Burns Out Barrels
First of all, barrel life varies greatly by cartridge, load, and firing practices. The largest contributor to the equation is the cartridge. More overbore cartridges will burn out barrels faster. More specifically, overbore refers to the relationship between the amount of powder in the case and the size of the bore that the powder travels down. For example, a 375 H&H and a 6.5-300 Weatherby have almost identical case capacities. However, there’s a huge difference in bore size between the 37 caliber bore of the Holland and Holland vs the 26 caliber bore of the Weatherby. This means the Weatherby will go through barrels much more quickly.
Another important factor in barrel life is the firing schedule. Putting rounds through a hot barrel will burn out a barrel much faster than letting the barrel cool between shots. I have had several sporter barrels over the years that I have shot very hot. Unsurprisingly, they have burnt out more quickly than barrels that I have let cool between groups.
Lastly, the loads that you are shooting also impact barrel life. Higher pressure loads will burn barrels quicker. Also, all things being equal lighter for caliber bullets tend to burn barrels more quickly. This is due to the faster powder burn rates and larger amounts of powder used to push the lighter bullets for a given cartridge.
How to Know When a Barrel is Burned Out
As discussed above, there are a lot of factors that play into barrel life. There’s a few symptoms that can tell you that your barrel is worn out. The first and most obvious is increasing dispersion. If your rifle consistently shot large sample size groups with a load and now the same load is shooting significantly larger, your barrel might be burnt out. Be aware of small sample size groups tricking you. One 3-shot group is not enough to diagnose a burn out barrel. A 20-shot group on the other hand is a strong indicator.
Another telltale sign of a cooked barrel is a drop in velocity. If your velocities inexplicably drop 40-60 fps with the same load your barrel might be cooked. This is due to wear in the throat of the barrel. Finally, if there’s a large increase in the standard deviations of your velocities that can also be a sign that your barrel is on it’s way out.
Should You Replace Your Barrel
Once you’ve recognized that your barrel is burnt out, you need to decide if it needs replacing. for many applications, a 1 MOA gun doesn’t have a meaningful impact on hit rates versus a 2 MOA gun. For hunting applications inside of 300 yards, rarely will a barrel start shooting poorly enough to warrant replacement.
Additionally, if the only symptom you’re experiencing is a velocity decrease, there’s likely no reason to replace your barrel. 60 feet per second is meaningless in almost all applications apart from some forms of competition shooting. However, for people shooting 1000 yard F-Class or 100 yard benchrest, any loss in performance merits a new barrel.
Hornady Empirical Data
Recently, the guys over at Hornady have published their extensive barrel life data from the 100’s of test barrels they have shot in the lab. This chart gives a rough guideline for different barrel lives of a given cartridge given the pressure of the ammunition and the firing schedule. I’ve attached a pdf of their results below. Most of the results match up with conventional wisdom, but it still makes for an interesting read.
Closing Thoughts
In closing, different cartridges, loads, and firing schedules can lead to wildly different barrel lifespans. By tracking dispersion, velocity, and standard deviations over large sample sizes you can determine when your barrels best days are behind it. Finally, depending on your application, you may or may not actually need to replace a barrel that is shot out. While most hunters will never shoot out a barrel, those that take practice seriously will eventually find themselves in need of a new tube. The data from this article will help avoid chasing your tail when that does happen.