SemiAuto for long range shooting8

Barrel Life

In Blog by Rich15 Comments

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.

barrel-life1

Match grade barrels can be had from many companies, like this one from Criterion Barrels…

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.

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Part of the reason I built my match rifle on a Rem/Age setup was to be able to quickly, and easy swap barrels out as they reach the end of their service life, the Rem/Age system allows the shooter to swap barrels in a few minutes with the proper tools!

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.

Wrapping Up

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!

Owner and Proprietor of AccuracyTech, LLC. Rich is a Firearms Enthusiast, Precision Rifle Competitor, and Writer. He is committed to bringing readers quality reviews and articles related to the Precision Shooting Sports. If you have any questions for him, please use the contact form on the site.

Comments

  1. Thanks Rich, I wonder what is the scientific basis that backs up the widely held claim that a barrel that is shot very hot with long strings will wear faster than the same number of rounds fired over a longer span of time with a cooler barrel. When we think of a hot barrel do we mean just too hot to touch 100C well that’s really nothing as far a steel is concerned is it? so does a hot barrel really wear faster or do we just think it does?

    1. Author

      Jeremy, I think this belief (I happen to believe it myself) has it’s roots in F Class and Benchrest disciplines. They have to shoot long strings, and when the wind drops they want to get it done while they have the advantage.

      I think it’s a somewhat anecdotal belief, but it makes sense. 50 Cals in the military have swappable barrels and head space tools because under heavy fire they burn out.

      Granted, bolt actions are another animal entirely. However, I do think the rate of fire can be a factor. Think of it this way, if you’ve ever heated up steel barstock and hammered it to make a screwdriver in shop class…what happens to the steel as it heats up? It becomes more malleable.

      I don’t think the throat is melting the way people picture it. However, heating it up with long strings of fire with high pressure rounds seems to take its toll on barrel life. It’s not going to burn out in 50 rounds or anything but I’ve seen 243 barrels going south at a little over 1000 rounds.

      I really think the tires on a fast car analogy fits very well. The harder you push the performance envelope the faster consumable components need to be replaced.

      I’ve also seen discussions where Dave Tooley and Frank Green (Bartlein) have chimed in on Snipers Hide. Dave Tooley posted photos of a barrel with fire cracking forward of the chamber. It gets hot enough and high pressure enough to put small cracks in the steel. Kinda neat to see I’ll try and find the thread tomorrow.

  2. Just a note of appreciation. Thank you for your well written and informative articles. An outstanding learning and reference resource!

  3. Great article! A couple other variables that come into play include case composition (steel vs. brass), bore finish (bare steel vs. chrome lined vs. nitrided) and cleaning methods used. Crown protectors or bore guides can do wonders in reducing cleaning rod damage!

    1. Author

      Thank you so much for the comment, it’s a real honor when some real industry people chime in! The cleaning rod comment made me chuckle, I had planned to include that as one of the largest factors for decreasing barrel life…over cleaning!! It’s a rifle barrel, you don’t have to be able to eat off of it and excessive cleaning with harsh solvents can do more harm than good. Especially when people start using pastes and abrasives on the bore!

      My Criterion barrel is so ridiculously accurate, I’m going to rebarrel my AR10 soon and I’m going to order up a Criterion for that too! Thanks again for the info, sir!

      1. Criterion Barrels Inc, you guys make great 6.5 barrels. Mine was very accurate but prematurely throat eroded n the 2000 count. I was looking for nodes on various powders and it was done just as I was finding a powder I really liked. I also have the 308 barrel that is chromelined and you guys claim is match grade. In fact I own two of them. It never performed as well as I liked, (maybe i never found a great powder for it) but its still very accurate many years later. I have surpassed the 7000 round mark and its still a great barrel. Why haven’t you guys tried to combine your chromelining technique or nitriding at least the throat on your 6.5 creedmoor barrel? I’d be interested in buying or trying a barrel like that. Isn’t it worth it to experiment with the future of precision shooting? Finding your nodes is a long process and I was switching from 4350 imr to H4350, varget, ramshot tac, 8208 and finding all of the recipies i wanted but by the time I got the info I wanted, the barrel was toast and I have to begin again.

        1. Author

          What Caliber, Mark? 2000 rounds is a little on the low side if talking about 6.5 Creedmoor. However, there’s always going to be throat erosion starting at round 1.

          How fast it erodes depends on a great many things. The caliber, round count, powders used, bullet, rates of fire, etc. Toasting a 6.5 barrel you’ve pushed hard in 2k rounds isn’t unheard of.

          Try giving our reloading by chronograph series of articles a look. It’s an amalgam of several reloading techniques and is designed to find an accurate load in less than 50 rounds of shooting. Once the barrel is broken in, of course.

  4. Rich I have learned so much from your web site my friend and I are just getting into PRS shooting and we both use your info all the time.

  5. Hey Rich, Great article. I’m new to this so forgive me if this has been answered 1000 times already. I have a Tikka T3 in .243 I see there are some 58 grain loads out there for varmint hunting that are claiming “Muzzle velocity: 3850 fps” Does the fact that this is a much lighter bullet, affect your statement “More friction, more pressure, more heat, less barrel life.” or would I be better off to find a load for those lighter bullets that will keep them around 2800 fps instead. The lighter bullet has to build less pressure than a heavier one, right???

    Thanks for your time

    Dean

    1. Author

      Dean, in general the more muzzle velocity present the less life you’re likely to get from the barrel. There are some caveats but in the context of your question…faster is not going to be better in terms of barrel life.

      However, I really recommend logging your rounds before you worry about it a lot. A 243 typically sees in excess of 1200 match accurate rounds. Obviously that depends on a lot of different factors. My point is 1200 rounds may take you years to reach depending how often you shoot and the volume of fire when you do.

      As to the pressure question, it’s probably roughly even, the difference in weight being responsible for different speeds at the same-ish pressures.

  6. Sorry, pal, I think you got it wrong. High velocity cartridges do not necessarily have short barrel life. Lower velocity does not necessarily last longer. Velocity has nothing to do with it! One factor alone makes more than 90% of the difference when if comes to barrel life! THE RATIO OF THE BORE SIZE TO THE CASE CAPACITY. That’s all there is to it. It doesn’t really matter if the case is fat and short, or slender and long. It doesn’t matter if the bullet is heavy or light. It doesn’t matter if the bullet is moving fast or slow.

    A big case with a lot of powder pushing a small caliber bullet will wear out your throat much faster than a small case with a fat bore. A .220 Swift is about as bad as it gets. A 300 AAC is about as good as it gets. Pressure in most modern rifle cartridges is about the same — 60,000~65,000 psi. The “magnums” do not really reach higher pressures. They simply have more volume in the case so they can burn more (slower) powder and flow more gas. The only question is how small of a hole you force the gasses through and how much gas actually goes flows through that hole. ALL of the gases start in the case, flows through the throat and down the barrel. How fast the bullet is propelled doesn’t change that. You can have a VERY heavy and VERY long bullet in a 6mm cartridge — something that looks like a pencil — leaving the muzzle at 1000 fps. You can have a short and light one leaving at 4500 fps. It doesn’t change the fact that you went no higher than about 60,000 psi and you are pushing basically the same amount of gas made by roughly the same amount of powder through the same size hole (assuming you seat the bullet out so the effective powder capacity is the same).

    This is why Tank Guns use a sabot to guide those darts out the barrel. That is why they don’t neck the bloody 120mm round down to 30mm and drive a dart through the barrel.If they did, the barrel won’t last more than a dozen shots.

    1. Author

      We’re all entitled to our opinions, Dwight. You say I’ve got it wrong but most of what you say supports what I’ve written. Your own examples of opposite ends of the barrel life spectrum, for example.

      What’s the difference in muzzle velocity between 220 Swift and 300 AAC? ~3000fps? When you say pressures in most modern rifle cartridges are the same, I think you’re overlooking something important. Those pressures are SAAMI and CIP standards for factory ammunition.

      People who shoot competitively in most precision shooting sports handload quite a bit. I don’t know any with the equipment or desire to load to pressure standards. They load for performance, namely speed. I doubt they’re all loaded to 60,000psi.

      Bore size and case capacity are certainly factors. No article can ever be completely exhaustive or all encompassing. My question for you is this: Can you name a high velocity cartridge with long barrel life?

      The only example that comes to mind is 223 Remington and it’s a bad example. Accuracy standards for an AR15 are quite different than a precision gun. I’ll ask some folks with 223 precision rigs what kind of usable and accurate life they get out of their barrels. I’m relatively certain it won’t be the thousands and thousands of rounds people shooting a 4moa AR15 are claiming.

      I said heat and pressure are the killers of accuracy. I stand by that whether you agree or not. There’s a host of new calibers doing exactly what you suggest should be avoided. They’re pairing small bullets with higher case capacity. Why? To use cooler powders, in larger quantities, to achieve higher velocities without burning up the barrel.

      6mm Competition Match using Retumbo or H1000 would be an example of this. Muzzle velocities exceeding 3100fps with accurate barrel life exceeding 3000 rounds.

      If heat doesn’t matter let’s burn up two barrels. We’ll do one with 20 round strings of fire and five minute breaks and one with 5 round strings of fire and 20 minute breaks. Shall we wager which expires first?

      Thanks for the good discussion!

  7. This is exactly why I created the Chamber Chiller rifle barrel cooler. The concept is simple: cool the chamber, where heat often sinks into the loaded cartridge which then causes higher pressure, and deliver cool air down even the longest rifle barrel with a high-output fan. Chamber Chiller is arguably the best rifle barrel cooler available, so get your prototype sample before they’re all gone!

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