A Borescope Tale of a Dirty Barrel (LOTS of Pics!)

[Agrivere]

A friend of mine a couple of weeks ago said he'd like to see some pictures of just what was going on inside a barrel after it's been cleaned in various ways, so I thought it would be fun to share what I see with my Borescope.  If you really don't want to know what's going on inside your barrel, then don't scroll down. 

First, some basics.  This is a 20" Krieger Service Rifle barrel on an AR-15 of course, with 2,102 rounds on it at present.  My loads are 23.4 gr H4895 with 77 Bergers for short line ammo, and 24.0 gr H4895 and 80.5 Bergers for 600 yards.  Don't think any of that makes much of a difference here, but there it is.

The pictures are all taken with the Lyman borescope, which I acquired when the barrel had 467 rounds on it, so first lets take a look at what the barrel looked like when it was clean with 467 rounds.  The following pictures show the rifling near the muzzle, the gas port, and the throat.







I found it interesting that the gas port had already eroded that much after just over 400 rounds, but as you'll see it hasn't really eroded much more since then.

The next set of pictures were taken when the barrel had 1,596 rounds through it, which happens to be how many rounds were on it when my friend asked, so I took a few pictures of the throat as a starting point.  The barrel is clean at this point, and it's easy to see where firecracking is beginning to show in the throat after this many rounds.





Next thing I did was shoot it!  I shot 130 rounds of mostly offhand practice, then 296 rounds at the Talladega Regional, and all I did was a light cleaning after the 130 rounds of practice, so the bore was more or less clean when I started the Talladega Regional, though I did not use any bore paste or anything more than a few patches and a pass with a bronze brush.

Before getting into the pictures, I'll go over what my usual cleaning routine is.  A couple of patches with Butch's Bore Shine on a jag to loosen things up.  Ten or so passes with a bronze brush, followed by several more patches with Butch's.  At that point the patches are coming out mostly clean, and honestly if you just want to remove the majority of the powder fouling and the majority of the copper, this ten minute cleaning routine will do that.  I'll usually follow this up with ten more passes with a nylon brush and another round of patches, which gets out a bit more fouling, but never a lot. Once this is done patches will come out totally clean.  Sometimes I'll run some Hoppe's patches down the barrel and let that sit overnight, which removes a tiny bit more fouling, but never much.

Anyway, this first set of pictures shows what the barrel looks like after 296 rounds, before any cleaning at all.  So if you ever wanted to know what a dirty barrel looks like on the inside, here you go.









That's what a dirty barrel looks like after 296 rounds, and it was, as you might expect, still shooting just fine at that point.  First thing I did was run my usual cleaning procedure, with Butch's, patches, and a bronze brush.  Next is what a "clean" barrel looks like after the patches are coming out clean.

Apparently the forums will only allow so many pictures to be attached, so this will continue in the next post.

[Agrivere]

Continuing, here's the barrel after my usual cleaning process.













This to me is the interesting part. There is carbon, starting in the throat, which no chemical or brush or patch I've found has been able to touch. This appears to me to be the start of the "carbon ring" some of us have experienced. You see it easily in the throat, and if you look closely you can see a "dusting" of carbon that extends to about halfway down the barrel. Note that you can see the faintest streaks of copper if you look very closely, though I never really seem to get enough copper in this barrel to even turn a batch blue, there's still just a tiny bit there.

[Agrivere]

The next (and last) thing I did was run Iosso Bore Paste through the bore. Can't imagine JB Bore Paste is any different in any important way, but I used Iosso because that's what I have. My process is to wrap a patch around an old bronze brush, give it a generous even coating of bore paste, and run it down the barrel from throat to muzzle five times. I repeated that twice here, for a total of ten passes with the bore paste. And here's what it looks like after ten passes with Iosso Bore Paste.















It's clear to me that those hard, crusty carbon deposits are gone now, and it also appears as though the firecracking is smoothed out considerably. Perhaps that cracking was only ever in the carbon layer? I don't know.

Does any of this ultimately make an accuracy difference we can see on the target? Again, I don't know. It seems to me that cleaning that stuff out is better than not cleaning it out, so I do it. Your mileage may vary!

One final picture, for any who are concerned about their throat and the wear there. This is my previous barrel, a Lilja barrel with 4,516 rounds through it. This barrel came out of service over the winter, and would still hold the ten ring at 600 yards, though X count was clearly dropping by that point in time.

[FiremanBob]

Thanks for the valuable info. Those are the sharpest photos I've seen yet from a Lyman borecam.

In the Lilja photo, was the throat cleaned with Iosso before the pic was taken? I'm wondering if all that cracking was in the carbon or actually in the steel.

[Agrivere]

Thanks for the valuable info. Those are the sharpest photos I've seen yet from a Lyman borecam.

In the Lilja photo, was the throat cleaned with Iosso before the pic was taken? I'm wondering if all that cracking was in the carbon or actually in the steel.

Honestly I don't recall, as I took that barrel out of service six months ago.  I think I did, but I'm not sure.  Would be simple enough to make a few more passes with the bore paste and see if it changes.  I'll see if I can do that.

As a side note, it's also easy to see why barrels start to lose accuracy somewhere around the 3,000 to 5,000 round range.  They will usually still shoot well at shorter distances, but at longer distances groups will start to open up noticeably.  For my purposes that barrel was well shot out, but would certainly still deliver acceptable accuracy at closer ranges, depending of course on what one considers to be acceptable accuracy.  When it was new it absolutely hammered.  When I took it out of service, not so much!

[Agrivere]

As FiremanBob asked, I pulled that upper back out and ran another ten passes with Iosso Bore Paste down the bore, just to see what, if any, difference it might make.

Here's before:



and here's after:



I don't see any significant difference.  Maybe a little smoother?  Hard to say, but nothing amazing.  A friend is sending me some of Tubb's TMS bullets, and as an experiment I'm going to run some of those through and see what they do.  Stay tuned!

[FiremanBob]

Thanks for the update. Wow, that's a lot of damage.

[Agrivere]

Even with the throat that rough it would still hold the ten ring at 600 yards. Groups were starting to open up though, and X counts were dropping. So that one is now out of service, but would still shoot shorter ranges with no difficulty.

[eagle223usa]

Very interesting.

[jmdavis]

I discovered something similar a few years ago when I thought my rifle was clean and a few passes of Montana Gold copper cream brought out additional copper and carbon. As a matter of fact, after letting it sit for 10 minutes the first patch came out a green tinged black, the second faintly green. Then according to the instructions I ran a couple of hoppes patches through and the barrel was much cleaner. I use JB or the copper cream every few hundred rounds now.

[sluggo]

Wow- very interesting stuff, how often do you use the bore shine?-

[Agrivere]

I personally use Iosso bore paste, though I think that particular detail does not really matter. Every 300 rounds or so I run the bore paste just to get that extra tough carbon glaze out. There are a number of different ways to do it, but I wrap a patch around an old bronze brush, give it an even coating of bore paste, and run it up and down the barrel five times. I can't see where it's doing any harm and it's definitely getting out that tough copper "glaze", which can build up and in time affect accuracy.

[sluggo]

Can you detect e a shift in the POI or relative accuracy immediately after cleaning?

[Agrivere]

For me, no, but I believe that depends a great deal on the barrel. My theory - and keep in mind this is just my experienced opinion so don't take this as hard fact - is that the higher quality the barrel, the less impact shift you'll see from cleaning. My competition barrels are all Krieger, Bartlein, Lilja, and such, and they are all hand lapped when they are manufactured. Most factory barrels will have lots of tool marks and imperfections which are removed (or never there to begin with) when a quality barrel is hand lapped. My theory is the more imperfections in the barrel, the more fouling shots will be needed to restore point of impact. This is not by any means to say that factory barrels or cheaper barrels won't shoot well, as many of them shoot great, but they may need more fouling shots to restore an equilibrium in the barrel.

To answer your question directly, my Lilja barrel would put exactly one shot outside the group when it was squeaky clean, then went right back to my normal zeros. My Krieger and Bartlein barrels don't "throw" any shots, and poi does not change when cleaned. Other barrels, well it depends. Some may take as many as five shots to "settle down".

I'll also note that smallbore barrels are rarely cleaned by competitive shooters (and when I say rarely i mean once a year at most) as it takes many, many rounds to re-deposit the lube in the barrel. All target grade 22 ammo has lube, which I'm sure we've all seen, and it might take 100 rounds or more before a cleaned barrel will really settle down again. They are often very finicky if you want the absolute maximum accuracy from them, and they don't obviously accumulate copper the way a centerfire barrel might.

This is really IMO more about barrels than cleaning ultimately, but if you guys would like to see some factory barrels and/or some old military barrels, and see what these tool marks and pitting and such looks like I'm happy to post some. I've got plenty of barrels like that too lol.

[sluggo]

Yes I would bevery  interested in those pictures- especially if you have a Swiss K-31, as I often hear that those rifles have exceptionally good barrels due to the cleaning regime used by the Swiss, I must admit that I really do not know how to critically evaluate the condition of a rifle's bore, but your posts really help with my understanding more- Thanks!

[Nevada Smith]

After seeing this thread, I can now appreciate the value of having a bore scope, especially when buying a used rifle!

Agrivere; can you show a Swedish Mauser M96 barrel if you have one?

[Nevada Smith]

Has anyone used Brasso or Mothers for bore cleaning?

I ask because they are a lot less expensive than Iosso and JB, and locally available in many stores.

And Brasso contains ammonia so it should "cut" copper.