Bullets ride unevenly on the lands?

Sartori42

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Jul 25, 2018
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This is the forum for stupid questions, right? :)

I thought when bullets get smashed onto the lands, that carved distinctive, rectangular, grooves into the bullets. I guess I assumed the wear across the width of the lands of the rifling would be even. The first time I look at the barrel of my Tikka T3X Varmint .223 with my new borescope, I see these stripes of wear down the middle of the lands (photo 1a). Each land has a wear stripe in the middle. It gets more pronounced towards the muzzle (photo 2a). I'm not worried or anything. The rifle shoots great. I'm just curious if this is normal? I mean, the bullets don't wear the lands evenly across their width? Things that make you go... "Hmmmm..."

Thank you for your time.

Steven
 

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Sartori42

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Jul 25, 2018
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breadbag,

I thank you for replying. I feel like I'm missing something obvious, but I don't know what it is.

It isn't easy (for me, at least) to show what I'm seeing with the borescope. The captures are stills and it's easier to see what I'm talking about live. Also, the worn stripe is more reflective than the rest of the land on each side of it. On the previous captures, I tried to keep the light off the wear stripe. I also turned the light to its lowest setting to try to reduce the glare off the worn area. I'll include one more capture here and explain a little more what I'm seeing.

In this capture, you can see the whole land, and a groove on each side. The lands are wider than the grooves in my barrel. You can see that the wear "stripe" is more reflective. The center of the image is the angled mirror, but below and to the left of the mirror, you can see the barrel itself. You can see the same lands and grooves there, they are just distorted by the camera. Even outside the mirror, you can see the wear stripe in the center of the lands.

Thanks again for your reply. I do appreciate it.
 

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Huskydriver

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breadbag,

I thank you for replying. I feel like I'm missing something obvious, but I don't know what it is.

It isn't easy (for me, at least) to show what I'm seeing with the borescope. The captures are stills and it's easier to see what I'm talking about live. Also, the worn stripe is more reflective than the rest of the land on each side of it. On the previous captures, I tried to keep the light off the wear stripe. I also turned the light to its lowest setting to try to reduce the glare off the worn area. I'll include one more capture here and explain a little more what I'm seeing.

In this capture, you can see the whole land, and a groove on each side. The lands are wider than the grooves in my barrel. You can see that the wear "stripe" is more reflective. The center of the image is the angled mirror, but below and to the left of the mirror, you can see the barrel itself. You can see the same lands and grooves there, they are just distorted by the camera. Even outside the mirror, you can see the wear stripe in the center of the lands.

Thanks again for your reply. I do appreciate it.
You have it backwards... The lands are the raised portions the grooves are the depressions fyi
 

lash

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I read your initial post yesterday, but honestly didn’t have an answer for you. Then I asked myself why it even matters in the least. Then I remembered that people who buy borescopes often find the smallest things to worry and concern themselves with. Then I went shooting and did some brass prep.

I realize that you are just curious and hey, I like to learn and know things too. If someone has a physical reason why you are seeing what you are seeing, then great. Otherwise, I’ve got more important things to do, like wondering why barrels are round and not toroidal.
 
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Threadcutter308

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OK, so you're asking because you're curious. That's fine.

Let me ask you this; If your rifle wasn't "shooting fine" and you thought this was the culprit, what would you do (or what could anyone do for that matter) to "fix it" ?

This appears to be another post where someone looks at the interior of their barrel with their brand new borescope and freaks out to a greater or lesser degree. Work up your loads, shoot the rifle and enjoy it. There is nothing you can do to "fix" this (even if it is a "problem"). The barrel will tell you when it's getting worn out/long in the tooth and needs replacement.

I have a borescope and it lives in the back of the bottom drawer of one of my tool boxes. There's nothing wrong with it, it's just that I don't use it very much.......
 
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Sartori42

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lash/Threadcutter,

As I said in my initial post, I'm not worried about this. I'm certainly not "freaking out". If anything, I was pleased to see that my recent, simple cleaning procedure ended in a good result. Good enough for me, anyway. So, conversely, I'm happy with what I saw in the borescope. I bought it (well, my wife gave it to me for Christmas) just because I am curious about how well my rifle cleaning procedure works. With handguns, I can hold the barrel up to a light source and see well enough down its length. With rifles, it isn't that easy.

So, it doesn't matter, except I'm just curious if someone else who has experience with a borescope has seen the same thing on their rifling. If it is normal wear, why would it wear so unevenly and in such a way? The grooves show even wear, but not the lands. I thought I understood how a bullet deforms over the rifling, but I guess my assumption was wrong. I wonder if someone knows the physical reason why this happens, or if my situation is unique. I was hoping for some enlightenment from the repository of experience within SH. Not a big deal. Sorry to be a bother.
 

Supersubes

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As others have said, that skid looking mark is the center of the groove, not the land. You’re mislabeling your pictures. Yes they all look like that. What would lead you to believe its wear? Run the scope back the the end of the freebore, where the lands start in front of the chamber. This is the area that takes a hammering which eventually kills the barrel.
 

Threadcutter308

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lash/Threadcutter,

As I said in my initial post, I'm not worried about this. I'm certainly not "freaking out". If anything, I was pleased to see that my recent, simple cleaning procedure ended in a good result. Good enough for me, anyway. So, conversely, I'm happy with what I saw in the borescope. I bought it (well, my wife gave it to me for Christmas) just because I am curious about how well my rifle cleaning procedure works. With handguns, I can hold the barrel up to a light source and see well enough down its length. With rifles, it isn't that easy.

So, it doesn't matter, except I'm just curious if someone else who has experience with a borescope has seen the same thing on their rifling. If it is normal wear, why would it wear so unevenly and in such a way? The grooves show even wear, but not the lands. I thought I understood how a bullet deforms over the rifling, but I guess my assumption was wrong. I wonder if someone knows the physical reason why this happens, or if my situation is unique. I was hoping for some enlightenment from the repository of experience within SH. Not a big deal. Sorry to be a bother.
Sorry, we do get a little crusty in our responses sometimes. In our (my) defense, there are posts about borescopes about once a week or once every other week and they all share a common denominator. That is, everyone (myself included, back then) "thinks" that barrels (bores) are perfect from the factory. That is not always the case, particularly concerning cosmetics. To give you a good example, when I first got my borescope, I ran it through my (very commonly known) name brand barrel and I was horrified at what I saw. There were "micro cracks" everywhere. Long story short; I had just cleaned my barrel and dry patched it. What I was seeing was lint from the last patch. I blew out the barrel with shop air and guess what ? No more "micro cracks". Talk about feeling silly.......But, it was a good learning experience.

Borescopes are not inherently bad, actually, they are good. However, in the example above, I was looking at an almost new/low round count barrel that I had already gotten a couple of groups in the .1's and numerous groups in the .2's out of. Bore scopes can provide good, incremental, point of reference information, but one must be careful to not "read too much" into what you are seeing on the computer/tablet screen. In other words, if the barrel shoots, you can pretty much ignore what you see (or think you see) with the borescope. When the accuracy starts falling off, then start looking at the bore, particulary the chamber end. It's actually not a bad idea to look every once in a while and try to keep track (to whatever degree possible) of the erosion taking place. Even then, it's damned near impossible to to "qualitatively quantify" where the "limits" are (and what to do about them).
 
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308pirate

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    Too much information (note that I did not call it knowledge) can be a bad thing
     

    Sartori42

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    breadbag, Huskydriver, Supersubes,

    When I'm wrong, I'll fess up to it. I looked again, and you are correct. The area I labeled as the lands, are actually the grooves, and vice versa. When I look at the borescope even now, I still see it reversed. However, I chased the rifling back to the leade and I can see that the narrower areas are the lands. I learned something here and it is appreciated.

    Threadcutter,

    Thanks for the nice, balanced response. I did see that borescope questions aren't very welcome here, but I felt like I was coming at the situation from a different angle than most. I'm not stressed, I'm just curious about what I'm seeing. Most of the time, I don't plan to use the borescope. To my mind, I validated my cleaning procedure. In the future, I may look again just to get a feel for how the barrel changes over time, but it won't be a frequent thing. Frankly, it's a pain to include a laptop and long borescope at the end of a cord into my work area.

    So, if anyone would hazard a guess, and then I'll leave this topic alone.... Why is the center of the groove more reflective than the area on each side? Could this be part of the manufacture of the barrel? Could it be uneven wear - that the bullet presses down with more force in the center of the groove, polishing it like I see? Something else? I get that this is normal, and I'm really not worried here, I'm just curious about what I'm seeing.

    Thanks again to everyone who has responded. I really do appreciate it.
     

    lash

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    breadbag, Huskydriver, Supersubes,

    When I'm wrong, I'll fess up to it. I looked again, and you are correct. The area I labeled as the lands, are actually the grooves, and vice versa. When I look at the borescope even now, I still see it reversed. However, I chased the rifling back to the leade and I can see that the narrower areas are the lands. I learned something here and it is appreciated.

    Threadcutter,

    Thanks for the nice, balanced response. I did see that borescope questions aren't very welcome here, but I felt like I was coming at the situation from a different angle than most. I'm not stressed, I'm just curious about what I'm seeing. Most of the time, I don't plan to use the borescope. To my mind, I validated my cleaning procedure. In the future, I may look again just to get a feel for how the barrel changes over time, but it won't be a frequent thing. Frankly, it's a pain to include a laptop and long borescope at the end of a cord into my work area.

    So, if anyone would hazard a guess, and then I'll leave this topic alone.... Why is the center of the groove more reflective than the area on each side? Could this be part of the manufacture of the barrel? Could it be uneven wear - that the bullet presses down with more force in the center of the groove, polishing it like I see? Something else? I get that this is normal, and I'm really not worried here, I'm just curious about what I'm seeing.

    Thanks again to everyone who has responded. I really do appreciate it.
    It’s not so much that bore scope questions aren’t welcome as much as the relative importance it is to some of us. Don’t take it personally.

    Okay, on to your question. Yes, the answer is this:
    Could it be uneven wear - that the bullet presses down with more force in the center of the groove, polishing it like I see?
    The bullet deforms from original diameter of .224” to help fill the grooves as heat and pressure form the base to fit.

    15E6CFCF-942A-4960-A718-BCD18162D2BD.jpeg