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how fast does a barrel wear

How Fast Does A Barrel Erode?

A match-grade barrel is a big investment for many shooters, so how much life you can expect from it can be a hot topic. This article will focus on an aspect of barrel wear that doesn’t seem to get much attention, but is especially important for shooters who compete precision rifle matches where you may fire 100-200 rounds, or if you use factory ammo where the seating depth isn’t customized to your specific chamber.

So, we all know that over time a barrel wears out. Barrels on a precision rifle are like tires on a car: while some may be better than others, none last forever. They all eventually get so worn that they need to be replaced. The wear happens gradually over time – it’s not like your tires looked brand new for the first 5 years, and then overnight they became unusable. Rifle barrels also erode gradually through use.

Rifle Barrel Cutaway Showing Chamber and Rifling

Over time the first couple of inches in a barrel that are just forward of the chamber will wear in a couple of ways: Cracks and pits will develop, and the lands/rifling will erode. (Note: I give a summary of why and how that happens, and what you can do to extend barrel life in this post.)

As the barrel starts to reach the end of its accurate barrel life you typically see two things: Muzzle velocity will start slowing down and/or groups may open up (i.e. precision starts to wane). In my experience, which of those happens first seems to depend on the cartridge you’re shooting and how many rounds you usually fire before allowing the barrel to cool. The whole concept of “accurate barrel life” is subjective and varies person-to-person. That’s why you see a huge range of round counts in forums when people talk about barrel life for a specific cartridge. What one shooter sees as acceptable precision or muzzle velocity can be different than another, which makes it hard to discuss barrel life in absolute terms. There are also so many factors that can affect how a barrel wears that a simple round count isn’t enough to make an apples-to-apples comparison.

In this article, I’ll focus on how quickly the lands of a rifle barrel usually erode (especially for mid-sized cartridges that are popular in precision rifle matches), and how some shooters manage those changes over the life of the barrel.

How Quickly Will the Lands Erode?

Short answer: “It depends.” But, I realize that isn’t helpful, so I’ll try to expand. First, it varies by cartridge, how hot of a load you’re running, and how hot you allow the chamber to get. If you fire long strings without stopping to let the chamber cool, it can erode much faster – maybe exponentially faster. In fact, it’s possible to burn out a barrel in one afternoon if you never let it cool (read article). It can even vary based on the barrel-to-barrel variation in steel, whether the barrel was button-rifled or cut-rifled, or the specific type of gun powder you use – so there are too many factors to make sweeping generalizations.

I have measured the barrel erosion on a few of my barrels (because I’m a nerd like that). On one of my 6mm Creedmoor barrels I used for PRS/NRL style matches, I measured the Cartridge Base To Ogive (CBTO) distance required to barely touch the lands on a brand-new barrel and then measured the same barrel using the same method after 1300 rounds (I documented round count, also because I’m a nerd like that). There was 0.077” of difference between the two measurements. That means the lands on my 6mm Creedmoor eroded 0.077” over 1300 rounds, which is an average of 0.0059” every 100 rounds (i.e. 0.077 ÷ 1300 × 100).

0.077” is a relatively small distance. To put it into context, a credit card is around 0.032” thick, so the amount of erosion we’re talking about over the life of a barrel is barely more than the thickness of two credit cards. Of course, I’ve heard of guys who kept shooting barrels until there was over an inch of rifling missing, but less than 1/10th of an inch is more common.

Since the 6 Creedmoor barrel that I measured the total erosion on over the life of the barrel, I’ve started using a new 6CM barrel, and I precisely measured the distance to the lands after the first 60 rounds (so when the barrel was fairly “broken in”) and remeasured at 203 total rounds, and between those two measurements this new barrel was averaging 0.00699″ per 100 rounds over the early life of the barrel. I’ll share more on that later in the article, but that means my 6mm Creedmoor barrels typically erode by 0.006-0.007″ per 100 rounds.

Note: For context of my shooting style (since so much of barrel wear depends on that), I’d say it’s extremely rare for me to ever fire more than 12 shots in a row before I allow the barrel to completely cool. I’d bet 80% of the time I fire 6-10 rounds and then allow the barrel to cool to near ambient temperature. I have two identical 6CM rifles so that when I practice, I can allow one cool while I use the other and swap back and forth so neither ever gets excessively hot. Around 60% of the ammo that goes through one of my 6CM barrels is Hornady factory match ammo, and the rest is handloads that are on the warmer side of the spectrum – but not way over pressure like some guys load.

I also measured the total erosion on one of my 6XC barrels that I shot out a few years ago and it was close to the same my 6 Creedmoor. My 6XC averaged very close to 0.005” of erosion every 100 rounds over the accurate life of the barrel. One of my shooting buddies also measured 0.005″ every 100 rounds over the life of his 6XC barrel.

An article from AccurateShooter.com talks about erosion on a 6.5-284 barrel, and the author says, “Since I started out, I’ve chased the lands, moving out the seating depth 0.086 inches (2.18 mm). I always seat to touch. … I documented every round through the gun and got 2,300 over four years.” That means his 6.5-284 averaged 0.0037” every 100 rounds (i.e. 0.086 ÷ 2300 × 100).

I searched the internet to try to find others who’d listed the throat erosion they’d experienced with different cartridges, but there are 2 fundamental issues we should be aware when it comes to data like this found in the wild:

Watch How To Measure the distance to the rifle lands video
  1. Many people don’t use a measurement method that is repeatable within +/- 0.002”. Honestly, I didn’t until recently. To learn how to measure this more precisely, watch these videos: Mark Gordon Method, Alex Wheeler Method.
  2. Many people don’t carefully document round count, and are simply ball-parking it (i.e. “about 1000 rounds” could actually be 800 or 1200).

Of course, either of those two things could skew the data, and if they’re both off it could lead to some bad conclusions. Having said that, I did find a forum post where a couple of the guys who seemed very detailed provided data they collected over multiple barrels:

  • 6mm Dasher: Averaged 0.004″ per 100 rounds
  • 6.5×47 Lapua: Average of 0.004” per 100 rounds

Have you measured your barrel erosion? Let’s create a little data repository by sharing what we’ve measured in the comments of this post! Please provide: cartridge, total measured erosion, total round count, and maybe share how confident you are in the data. Share your data in the comments!

Here is a summary of the numbers we have so far to work with:

CartridgeAvg. Erosion Per 100 Rounds
6mm Creedmoor0.006-0.007″
6XC0.005”
6mm Dasher0.004”
6.5×47 Lapua0.004”
6.5-2840.004”

The cartridges above are representative of popular precision rifle cartridges used in competitions. I’d expect that cartridges that are more mild for their caliber size, like the 308 Win, would erode slower than what is shown. Likewise, I’d expect magnums, like a 300 Norma Mag or even 7mm Rem Mag, to erode faster than what is shown here. Hot-rod cartridges like a 22-250 or 22 Creedmoor that are pushing a lot of powder down a smaller caliber bore will likely also erode measurably faster. One of my closest friends has a custom rifle chambered in 6.5x280AI (yes, a wildcat of a wildcat – he’s a velocity fein). That is an excessively overbore cartridge, and he told me by 1200 rounds the lands had eroded by almost 0.200″! He didn’t have exact numbers, but his erosion was likely around 0.015″ per 100 rounds. Unfortunately, I’m not aware of anywhere to find that kind of data for different cartridges, but I’m hoping you (my readers) will share any data you’ve collected in the comments.

The Deception of Averages

Now, we should be careful to understand that the numbers above are “on average” for every 100 rounds. I didn’t measure the exact erosion every 100 rounds, and it may not be linear across the entire life of the barrel. It could be faster over the first 100 rounds, and slower over the last 25% of the barrel life – or vice versa.

Over the past couple of months, as I’ve become more interested in this topic, I started measuring the throat erosion on my rifles more carefully and more frequently. I recently measured the distance to the lands on a new 6mm Creedmoor barrel after the first 60 rounds and found the CBTO dimension to touch the lands to be exactly 2.1660” with Hornady 110gr A-Tip bullets. A few weeks later, the same barrel had 203 rounds down the tube, and I measured it to be exactly 2.1760”. I actually repeated the measuring process twice, because I thought it was so unlikely that it’d have eroded exactly 0.0100” over the last 143 rounds – but I ended up with the same exact number both times, which says something about how repeatable my measurement method is! The lands eroding 0.0100” over 143 rounds equates to an average of 0.00699 per 100 rounds (0.0100” ÷ 143 round count × 100 = 0.00699″ per 100). So, over those rounds early in the barrel’s life it was very close to 0.007 per 100 rounds (at least for that barrel), unlike my last barrel which averaged 0.006” per 100 rounds over the full life of the barrel. I will say my new barrel is a different brand, and I’m using a different powder and bullet design than I was on the old barrel.

I say all that just so we don’t see any of these “average per 100 rounds” as the unquestionable truth for how a barrel will wear. Not only may it vary from one person to another, but for one barrel to another – or even vary over the life of the same barrel. More detailed measurements would need to be collected at frequent increments to determine the exact pattern, although the results would likely vary by the specific barrel, load, and other factors. (Note: If anyone knows of good research studies related to this that would be applicable, please share them with us in the comments.)

I tried to illustrate 4 examples in the chart below that all “average 0.004 inch per 100 rounds over the life of a barrel,” but each varied in how they got there. The only thing we know for sure, is what your specific barrel does as you shoot it won’t perfectly match any of the examples. It would be a very interesting to see future research with multiple data points through the life of the barrel for several types of cartridges and barrels.

Chasing the Lands

So, if we know the lands erode as the barrel wears, how does that effect our bullet jump? (What is bullet jump?) As the lands erode, bullet jump will naturally increase by around 0.004-0.007″ every 100 rounds for these mid-sized cartridges.

Let me call to mind two quotes I shared in the last post:

So, we know that changing bullet jump by 0.002-0.005 inches can potentially have a dramatic affect precision. That is why many precision shooters who reload will extend their seating depth regularly so their bullets will be seated further out as their barrel wears, often called “chasing the lands.” For example, if you are shooting with the bullet 0.010” off the lands, and the lands erode 0.030”, you now need to seat the bullet out 0.030” further to maintain 0.010” of bullet jump. If you don’t adjust seating depth, your bullet would be jumping 0.040”, which would likely no longer provide optimal precision.

It is critical for everyone to understand this, so I’ll quickly run through an example to make sure we’ll all on the same page: Let’s say you found that 0.020” of bullet jump was optimal for one of your rifles, and on your brand-new barrel that meant the CBTO dimension for a loaded round measured 2.500” to achieve that 0.020” jump. Then after 200 rounds, let’s say the lands had eroded by 0.010”. That means we’d adjust the seating depth on our die so the CBTO of a loaded round is now 2.510”, and that should put your bullet back to that relative distance of 0.020” jump to the lands again. The lands will continue to recede over time, so this is something you must repeat regularly to maintain the same bullet jump.

Important: Adjusting your powder charge or seating depth will affect your chamber pressure, so, as always, you should be careful when changing a load and watch for signs of excessive pressure. The Sierra Reloading Manual says that adjusting seating depth to match your rifle’s throat/freebore and maximize accuracy “is fine, but bear in mind that deeper seating reduces the capacity of the case, which in turn raises pressures. Going the other way, seating a bullet out to the point that it actually jams into the rifling will also raise pressures.”

What Does This Mean For PRS/NRL Shooters?

PRS Rifle Match

Based on info above, we can assume many mid-size cartridges popular in precision rifle competitions average around 0.004-0.007” of erosion every 100 rounds. Think about what that means over a two-day match where you fire 200 rounds. By the last stage your bullet jump could be 0.008-0.014” more than it was on the first stage! If the experts are saying that changing bullet jump by 0.002-0.005 inches can have a “dramatic” impact on precision, what will 2-7 times that much do?

As we saw in the last post, the overwhelming majority of professionally published materials from trusted experts suggest for optimal precision you should seat the bullet into the lands or very, very close to the lands. If you are seating bullets very close to the lands for minimal jump, like 0.010″ off the lands, then by the last stage your jump may have doubled – or more!

Some of you may already be thinking that you could simply start loading your 200 rounds of match ammo with increasing COAL. We just need to seat the bullet out 0.001” more every 16.67 rounds, right? Stop! Before we add yet another layer of complexity, what if we’re coming at the problem the wrong way? I’m not asking you to accept some radical new approach, but what if we simply pause for a minute to explore that idea.

Knowing that we’ll be in matches that require 100-200 rounds, maybe our priorities should be different than other shooting disciplines. In some of those other types of competitions, like Benchrest, shooters are literally loading their ammo at the range as they’re shooting. Other competitions, like Extreme Long Range (ELR), are much lower round count, and shooters need less than 50 rounds to compete over one weekend.

What if instead of looking for the one exact bullet jump that provides 100% optimal precision, we instead looked for the bullet jump that is very forgiving AND still provided good precision over a wider range of jumps?

Now let’s think about the guys who aren’t reloading: If we’re trying to optimize a rifle chamber for a shooter who plans to simply shoot match-grade factory ammo, could we optimize the freebore of the chamber to be a bullet jump that would continue to provide good precision over a longer period of time as the barrel wore? It seems like they might have similar priorities.

What if absolute peak precision might not be the only priority we are trying to balance? I totally understand that in some shooting disciplines, like Benchrest, optimal precision is the absolute highest priority and nothing else is even a close second. But, what if we came at this from a different angle and tried to see if there was a way to balance priorities of both precision and a forgiving bullet jump?

The graphic below is a matrix visualization of what I’m trying to describe. The yellow dot labeled A is a load absolutely optimized for peak precision, but is very sensitive to changes in bullet jump. However, the green area labeled B represents something that has very good precision, but is much more forgiving in terms of bullet jump.

Up Next

The next post will share some interesting new research that has never been published and is focused on this exact topic: If we were looking for the most forgiving bullet jump that still provides good precision over a wide range of jumps, what would we find?

Read about it here: Bullet Jump – Is Less Always Better?

About Cal

Cal Zant is the shooter/author behind PrecisionRifleBlog.com. Cal is a life-long learner, and loves to help others get into this sport he's so passionate about. Cal has an engineering background, unique data-driven approach, and the ability to present technical information in an unbiased and straight-forward fashion. For more info, check out PrecisionRifleBlog.com/About.

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37 comments

  1. This is a great article with a chart that shows what calibers basically wear faster than other and the ones that last a long time like the 30BR, 223,308 many other are considered over bore like 243 and many more that wear a barrel fast

    https://www.accurateshooter.com/technical-articles/overbore-cartridges-defined-by-formula/

    Frank

    • That’s a great resource, Frank. I actually thought about that specific post when I was talking about magnums going faster and 308’s going slower. I’ve read that article more than once, actually. Very helpful. I’ve even played around with the Excel spreadsheet to help you estimate “useful barrel life” that is a related to post to that on AccurateShooter.com: https://www.accurateshooter.com/technical-articles/excel-formula-predicts-useful-barrel-life/. That one tries to take into consideration a few of the factors that affect barrel life like the details of your load and how that relates to the bore diameter. Both of them are great, and I thought about linking to them … but I can definitely go overboard often times with the amount of detail I have in these posts. But I do appreciate you sharing that.

      Thanks,
      Cal

      • Hi Cal,
        Have you tried to apply Nathan Foster’s method of regularly cleaning the barrel with an abrasive paste like JB bore to keep on top of the fire cracking ?

        Nic

      • I have, Nic. I actually do follow Nathan’s process for barrel cleaning. He had a really good article on that I read a few years ago and have been following it ever since.

        Thanks,
        Cal

  2. This reminds me of the optimal charge weight (OCW) method… I like it! Cal, you’re a man after my own engineering heart :-).

    Have you tried combining the two? Will that be in the next post? Looking forward to the next post! Thanks!

    • Ha! Samuel … we do think too much alike. I will actually draw a few parallels to the OCW method in the very next article. That is very similar to how this research was done, except it was even widened beyond that concept in another way. I don’t want to give away too much, so I’ll just say to stay tuned!

      Thanks,
      Cal

  3. Funny we think alike….. I’ve been measuring this exact variable in my .25 Creedmoor using Krieger cut rifle blanks, over 2 separate barrels and over 4000rds fired I’m averaging .005″ per 100rds fired….. most all these are 10 shot strings of fire and the past 2 years of match use a couple times per month.

    What I’ve found is that the most consistent way to accommodate this is to start with a little jump in the OAL, in shoot for .020″ and test at .040″ to see if I notice any effects in precision, typically not…. it’s convenient that run my brass in 500 count lots so I increase my OAL .020″ every loading cycle…. and replace the barrel every 2k rds, needed or not!

  4. When I was in the army I set 600 record at the all army matches with an M-14. The barrel was air gauged and went off scale at 2 inches from the muzzle. The barrel was removed and sectioned no visible rifling 4 inches in front of the chamber. The barrel had 37,000 rounds through it. Some barrels last longer than others.

    • Ha! That’s the kind of stories I’ve heard before. Thanks for sharing, Dick.

      Did you ever start to see drops in muzzle velocity as the barrel wore?

      Thanks,
      Cal

  5. Cal, you really struck a nerve for me…Please include your analysis of:
    1) how case shoulder angle & neck length affect the powder venturi burn patterns against either the disposable case and or barrel throat/leade/lands and thus erosion. Example 6mmSLR vs .243Win
    2) how reduction of required bullet obturation forces thus peak pressures/temperatures for blended boron nitride (HBN i.e. Tubb’s) coated bullets enhances throat life ( you have used the more common momenclature “barrel life” mainly in this article but other than some muzzle escaping gas cutting isn’t it really the throat that wears first causing loss of precision?
    3) how “Nitriding” barrels i.e. Ferritic NitroCarburizing (FNC) via either saltbath or nitrocarburizing methods yield a throat/leade more resistant to heat/pressure erosion. My Blasers are German tough.

    • Hey, CR. Those are all great questions and I wish there was research available that speaks to those, but I’ve never come across any that is publicly published. Unfortunately for all of those topics, you’d need data over a very large sample size to draw meaningful conclusions, because there are so many other variables that could potentially be at play when it comes to barrel wear. That research project would likely need a government-sized budget, not a blog-sized budget! 😉

      I will say that I’d be equally as interested in you in finding the answers to those things, so if anyone reading this know of studies that have been done please share a link with us all here in the comments!

      As always, thanks for sharing your thoughts, CR!

      Thanks,
      Cal

    • Cal,
      I was always under the presumption that the 6.5-284 was considered a real barrel burner. Your data, although limited, does not back that assumption up. As you get more data, there may be some other real surprises concerning “barrel burning” calibers. Keep up the great info.

      • Me too, Wade. I figured it’d be similar to the 6mm Creedmoor, honestly. Of course these are VERY small sample sizes (ie your mileage may vary). I suspect you would see that over a larger sample size. Ultimately, I was just trying to give everyone context for how much your barrel changes and how quickly it changes. It’s something that if you aren’t paying attention and actively managing it likely will affect group size. Now how much it affects it and “if it matters” probably depends on the application or level of competition you’re in. But, it does change by what respected experts in the field would say is “dramatic.” So whether it is 0.004” or 0.010”, it’s something we might need to think about. I’d just suggest starting to measure it on your rifles and change the seating depth to whatever you actually measure it to be, not what you guess it is. That’s at least another big thing I’ve learned through all this.

        I definitely think the next post will help put all this into context, or at least present a new way to look at it. Stay tuned!

        Thanks,
        Cal

  6. My 6.5 CM RPR barrel that was fantastic (.34 moa avg. all 5 shot targets 100-400 yards) through about 2800 rounds went south fast to about a .7 moa.

  7. Hi Cal,
    Great article and nice video on checking your distance to lands!
    This works great for the AI barrel system, but what if your rifle/barrel uses a barrel extension?

    Such as the Sako TRG M10, Barrett MRAD and Desert Tech SRS.

    • Hey, Marty. Great question. There is another method to measure the distance to the lands that Alex Wheeler came up with and it is just as accurate and repeatable, and I think you’d need to use that method for those other configurations where headspace is controlled some other way. You have to disassemble the bolt, but I’d think you’d be able to do that on those other setups.

      To learn more about that other method, you can go to this link and scroll to the bottom of the article. That’s where I talk about the Wheeler method to measure this.

      https://precisionrifleblog.com/how-to-measure-the-distance-to-the-lands-on-your-rifle-barrel/

      Thanks,
      Cal

  8. 9/22/2019-03/25/2020 6mm Creedmoorr 26” Bartlein Gap#7 contour, 7.5 twist, 3 X 100 round local matches, 40.5gr H4350 3030 fps. Starting BTO = 2.2385. 697 rounds BTO = 2.2600. Therefore .003”/100 rounds.

    • Berg 105 Hyb Targ

    • Thanks for sharing, Jeff! Wow, that is quite a bit different than my numbers. My new barrel is very similar (Bartlein, 1:7.5 twist, 26”, Heavy Palma contour) and I’m also using H4350. That last measurement of 0.007” per 100 was after a practice session and one 100 round local match (143 total), so even the use at least seems similar.

      Would you mind if I asked how you measured the distance to the lands? Were you using the Alex Wheeler method where you disassemble the bolt or the Mark Gordon Method where you remove the barrel?

      Thanks,
      Cal

  9. ->Do we have any solid data on the use of Hbn coated bullets reducing throat erosion AT ALL?
    ->How about the durability of stainless steel v.s. chrome-moly barrels?
    ->Any data on cryogenic treatment of barrels?
    ->Are chrome lined barrels more resistant to throat erosion?
    *OR is 90% of throat erosion due to heat?

    • Great questions. I am unaware of any independent research on those topics. Any one else reading this know of any?

      Thanks,
      Cal

  10. G’Day Cal,
    Norma did a great review on how bullet coating (in their case, moly) affected barrel life … a real eye opener. Yes, in the example they provided, the case for barrel life extension of coated bullets was impressive to say the least. A singular sample test. Hardly conclusive, but very challenging! See accurateshooter articles.
    Our testing here supports Norma’s principle findings, if not the numbers.

    As for Eric B’s other questions, no leads to offer there. I personally suspect that material selection will have some influence, as will production methodology (hammer forged vs button rifled, etc.) affecting material structure, toughness, hardness, among other things.
    The challenge for comparison will always be in the consistency of standards by which performance is assessed. As you have stated already, a very subjective benchmark. To develop an agreed standard of performance, and measurement of outcomes would be a very financially and time consuming exercise given the multitude of variables … sounds like fun!

    That said, throat erosion is caused by a number of factors that are difficult to separately quantify:
    1. frictional heat generated by the bullet rubbing on the steel
    2. chemical heat intensity and duration from the rapid burn of the propellant
    3. abrasion from propellant residue (carbon is one of the hardest materials known, and the more we leave in the throat, the greater the abrasive sand papering effect)

    Bullet coatings can reduce frictional pressures by around 30% according to Quickload, and this must reduce frictional heat. Which is best …?
    Many shooters don’t realise however, that the Wm2K (a measure of thermal transfer) of a jacketed lead bullet is less than that of steel. This means that more of the frictional heat is being transferred to the barrel, rather than the about to be rapidly disposed of bullet.
    Copper has a Wm2K four times that of steel, which means that much of the frictional heat should be absorbed by the disposable bullet. (The percentages and importance of this issue are not known, but temperature variance is easily measured)

    It’s a fascinating and extremely interesting subject requiring a great deal more research. Like all research, we shall probably end up with more questions than answers, but isn’t that half the fun?
    Great approach and insight Cal. Good work. Thanks for what you are doing …
    Cheers
    Steve

    • Wow, Steve! Thank you for the very thoughtful and informative reply. I really appreciate you sharing the insight! I 100% agree with your statement, “It’s a fascinating and extremely interesting subject requiring a great deal more research. Like all research, we shall probably end up with more questions than answers, but isn’t that half the fun?” YES! Any real research just seems to uncover more questions than answers. Honestly, I’m honestly a bit skeptical of studies that have clean findings and no additional questions, because that just isn’t the way it ever works out for me. 😉

      Thanks,
      Cal

  11. There are some other considerations that can throw your measurement off. Barrels rarely erode evenly around the 360 circumference of the bore. Generally the lands are within .020″ of each other but you could very well have one land eroding slower than the others due to the metallurgy. This would give you a misrepresentation that the erosion is less than it actually is. The type of rifling is also factor. 5R rifling tends to erode faster than cut rifling with wider lands and narrow grooves. These variables can give the unknowing shooter a false impression that one caliber or cartridge has superior life than another or one barrel manufacturer is superior than another’s.

    • Great points, Philip. I hadn’t thought of those, but I could see how that’s likely true. Too many variables to make many sweeping generalizations. My advice is to measure your own barrel and adjust seating depth based on that. That’s what I’m personally doing.

      Thanks for sharing!
      Cal

  12. I loaded only Hornady 108 ELD’s at about 3050.
    Initial CBTO-2.183…. after 1940 rnds fired,
    CBTO-2.207
    Erosion =0.024

  13. Cal,
    Is it possible that some of the factors of the erosion are things like: 1) cartridge vol : caliber (ie a given volume of hot gasses forced through a smaller opening will erode more than the same vol of gasses through a larger opening) 2) the heat generated by the declaration of a specific powder (QuickLoad software gives specific heat ratings for the various powders, and the military adds nitroguanadine to propellants to lower the gas temp and extend large caliber bore life) 3) how completely the powder is ignited (at peak temp when it goes across the throat) as opposed deflagrating as it travels down the barrel) ?
    [My apologies for typos sending this from a phone, and I am old]

  14. Cal,

    I used to be able to print your article and the following comments. For the past few months, I have been unable to print the comment section. Is there something I may be doing wrong?
    Thanks.

  15. Here is the data from my PVA 6creed barrel that I have tracked. Shooting a 105gr RDF with mild H4350 load I got 0.007” of erosion over the first 420 rounds, 0.005” over the next 418 rounds, 0.001” over the next 172 rounds and 0.004” over the next 94 rounds. This gives a total erosion of 0.017” over 1104 rounds or an average of 0.0015” per 100 rounds.

    • That is very interesting, Mike! The breakdown of how it varied over time is really helpful. I think that’s the first time I’ve seen a breakdown like that. I’ve started measuring my own rifles like that, so I hope to have a similar understanding of erosion over the life of the barrel at some point in the future. I really appreciate you sharing!

      Thanks,
      Cal

  16. I wonder if there is less or more erosion over time if you chase the lands?

    • That’s a great question that I honestly haven’t thought about it. My suspicion is that if there was an effect, it would be very small and possibly “in the noise”. I could see that there could potentially be more or less gas blow by depending on the bullet jump you were using, and if it were more those hot gases may cut more at the barrel. On the other hand, I remember Harold Vaughn cited research that proved chamber pressure spiked when seating into the lands … and higher chamber pressure likely means less barrel life.

      I readily admit I don’t have a professional background or training in internal ballistics, so I’d defer to anyone else reading this that might have insight. Please chime in if you do!

      Great question! That’s how most things work in my experience … the more you learn, the more questions you have!

      Thanks,
      Cal