Here’s a term you’ve likely heard thrown around a lot, lately: Barrel Life. We’re going to discuss what barrel life really means and how it works since it’s been coming up in articles lately. I want to make sure everyone has a good grasp of exactly what barrel life is. I want to make sure people understand what factors affect barrel life. Lastly I’d like to give some rules of thumb for lifespans of different calibers and what a person can reasonably expect for barrel life in those calibers.
What is Barrel Life
We’re going to start with a good working definition of the concept before we start discussing things that influence barrel life. For the purposes of this website, and the tactical shooting aspects of precision marksman ship, barrel life is the expected number of rounds through a barrel before accuracy degrades below one minute of angle at 100 yards distance. Obviously you’re pushing copper and lead through the barrel at pressures around 60,000 psi or higher. That has an effect on the barrel and how long it will last. I’m suggesting we use the 1 Minute of Angle standard because…it’s pretty standard. If the rifle won’t hold 1 MOA it’s no longer considered ‘accurate’ for the purposes of precision shooting.
However, you have to understand this is a fairly loose definition. While 1 MOA might be acceptable for most people, it’s not going to be acceptable or unacceptable for everyone. Hunters shooting minute of deer at 100-300yds on average can probably get away with 1.5-2.0 MOA without suffering any performance issues on a hunt. Meanwhile Benchrest guys who win or lose in differences of 10ths of an inch are likely not going to feel 1 MOA is anywhere near acceptable. So my first suggestion when talking about barrel life is to make sure you keep context in mind. If your buddy buys a factory Remington that’s shooting 1.5 MOA and he’s having a good time, then mission accomplished! We don’t all have to have 1/4 minute rifles. Different people have different requirements of their rifles and gear.
What Affects Barrel Life?
Heat and pressure. The higher the pressure in the cartridge, the more wear and tear on the barrel. Likewise, heat itself is an issue. For an example, long and rapid strings of fire where you heat the barrel up quickly and repeatedly force high pressure projectiles through it, that’s going to put some wear on your barrel. On the other hand if you have a hunting rifle that might see a few rounds every season for sight in and a handful on hunts, that’s a relatively low round count and slow volume of fire. I’m not in the barrel producing industry so I don’t want to talk out of my depth on much of the science behind this. I’m not out to mislead anyone.
However, if you keep the basics in mind you begin to understand why a .243 Winchester has a lower expected barrel life than a .308 Winchester. Muzzle velocities for the 308 Winchester are typically around 2600fps. While the 243 Winchester often sees muzzle velocities between 3000-3200fps+…that’s a large difference. You’re pushing that smaller bullet through the barrel a lot faster. More friction, more pressure, more heat, less barrel life. That’s putting it as accurately as I can without oversimplifying or wandering off into the land of physics and math that gives everybody a headache.
What’s Wearing Out?
A lot of people mistakenly think that the rifling is what wears out in a barrel. While there are stories of this happening on barrels with really ridiculous numbers of rounds logged through them, it’s fairly rare. Typically what wears out on your barrel, is the throat. The throat is the part of the chamber between where the brass runs into the chamber wall, and the rifling engages the ogive (pronounced oh-jive) of the bullet. If you’ve ever heard that Remington’s have a long throat, what you’re hearing is somebody referring to a longer than spec space between the top of the brass and the rifling. This isn’t a bad thing, it means you can seat bullets farther out which gives you more area within the case for powder.
You may have heard certain Gunsmith Shops offering to chamber or throat a barrel for a specific bullet? If it’s a bullet that’s longer than spec and you tried to load it in a chamber cut to cartridge specifications, you would have to seat the bullet deeper in the case. If the throat is cut longer to accommodate the longer bullet, you aren’t eating up case capacity using a longer projectile. The Ogive (pronounced oh-jive) of the bullet is the part near the front of the projectile that will engage the rifling first. This is also the area towards the end of the throat where the bullet and rifling first make contact. Over time, and many rounds fired, the throat will actually erode as it’s burned away by heat, friction, and pressure.
Other Barrel Life Concepts
As the throat moves deeper into the barrel, and it’s eroding, the bullet doesn’t have the same smooth transition between the chamber and the rifling. You start to see accuracy degrade when this happens. This is why hand loaders need to measure their chambers when they work up their first hand load, and periodically as they progress through the usable barrel life of the barrel. If the throat is eroding back, you can track how far it’s moving and how many rounds it’s taking to move it. Since the seating depth of a bullet can often be a factor in the accuracy of the bullet, you want to maintain the relationship between where the bullet starts and how far it ‘jumps’ before it engages the rifling.
As the throat moves back, there’s a phrase ‘chasing the lands’ that applies. You can seat the bullet farther and farther out of the case to keep it the same distance from where it engages the rifling of the barrel. Say you’re shooting a 243 Winchester and you get great accuracy jumping a Berger Hybrid 0.020″ to the rifling. As the barrel wears, the bullet has to jump farther, unless you seat the bullet farther out of the case to maintain the jump distance. Then you have another problem, you’ve changed the case capacity and the pressure behind the bullet. Typically those that ‘chase the lands’ will add a little powder to maintain the same case pressure and velocity. By doing so they keep their ammunition and it’s relationship with their barrel consistent over the life of the barrel.
Here’s that word again. Perspective. Depending on how fast your throat is eroding, and how tolerant of seating depth changes your projectiles are, those factors will determine whether or not something like chasing the lands is worthwhile. I expect to run into accuracy and velocity loss around 1800 rounds with my 6×47 Lapua, which is very similar to a 243 Winchester. The mighty 243 Winchester will start seeing accuracy and velocity loss anywhere between 1000-2000 rounds depending on how the ammunition being fired through it is loaded. The hotter and faster you push the bullet, the lower your usable barrel life becomes. 308 Winchester will typically go around 5000 rounds of usable life. 6.5 Creedmoor, 260 Remington, 6.5×47 Lapua are all somewhere in the 2000-3000 round spectrum.
Remember, a lot of this has more to do with the ammunition, than the barrel. If you are a competitive shooter, pushing for all the speed and ballistic advantage you can muster from the rifle you’re going to burn through the barrel faster than somebody shooting a mild, recreational, factory ammunition offering. Barrels on a rifle are like tires on your car. The faster you drive and the harder you push through corners the quicker the rubber wears and you need new tires. Same concept with barrel life. Try to look at it that way, it’s not a big deal. If you shoot often enough to burn out a barrel, don’t be down about it! Pat yourself on the back, you officially shoot more than most people out there…you’re a true Sportsman! If you have anything to add or a question, please drop it in the comments below!