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The folks in the Kimber custom shop recently rebarreled a Model 84M Montana for me. Since I received a Gradient Lens “Hawkeye” borescope as a birthday present I thought this would be an excellent opportunity to watch what was actually happening during a barrel break-in.


The folks at Kimber test-fired two brands of factory ammunition in the rifle prior to returning it to me and included the test target.  A three-shot group was fired with each of the two brands of factory ammo, plus one shot as a “spotter” with one of the brands, presumably to confirm scope settings, for a grand total of seven rounds through the new barrel.

Upon receiving the rifle I first cleaned the bore down to bare metal.  Prior to reaching bare metal, but after removing the majority of the powder fouling I took a peek with the borescope.  There was quite a bit of jacket fouling on the lands.  The jacket fouling extended almost all the way from muzzle to chamber.  I used multiple applications of Sweet's 7.62 to remove the copper fouling.  After removing the Sweet's and wet brushing I finished the cleaning job with multiple passes with J-B® Non-Embedding Bore Cleaning Compound to help smooth the new bore.  After cleaning out the JB I again inspected the bore with the borescope.  I noted what appeared to be a few minor imperfections in the barrel, but overall it looked pretty good.  (It should be noted that I’m still getting used to looking at things through a borescope and that it will take me a while to get a feel for the significance of what I’m looking at as the borescope does feature 25x magnification.)


On the recommendation of a professional barrel-maker I’ve been experimenting with firing three shots and then cleaning, rather than the often-recommended one shot and clean break-in regimen. After firing the first three rounds I cleaned the barrel using the following technique: 

One clean patch saturated with Ed’s Red.  The first patch is pushed straight through the barrel without any stroking.  This is to remove residue, which could scratch the bore if worked back and forth.  Next another clean patch soaked in Ed’s Red.  This patch is stroked back and forth in perhaps three to four-inch strokes, gradually working from the breech end to the muzzle.  The same patch is then turned over, a bit more Ed’s Red applied, and the procedure is repeated.

Next comes a thorough wet brushing.  I keep a separate container of Ed’s Red just for dipping the bronze brushes.  (I have it on good authority that even a good quality bronze brush can scratch a bore if used dry.)  I run the brush all the way through the barrel and then pull it back.  On the third cycle, I leave the brush hanging out of the muzzle end and I wet the brush with more Ed’s Red using a bottle with a small spout.  The brush is then run for at least another three cycles through the bore.  Brushing is followed by a couple of clean dry patches to remove the loosened crud and excess solvent.

I use Sweet's 7.62 to remove copper fouling, so I wet a patch with denatured alcohol to remove as much solvent as possible.  (This should help the Sweet's to be more effective.)  I turn the wet patch over and run it through the bore one more time and then follow with a dry patch, also turned over and run again.

I use an under-size jag and a patch to apply the Sweet's to the bore.  I’ll re-wet the same patch and run it through the bore again two more times to ensure an even distribution of the Sweet's.  I then let it work for about eight minutes. (The instructions on the label say no more than fifteen minutes.)  After the eight minutes are up, I run a dry patch through the bore and check to see how much blue (indicating copper fouling) is on the patch.  This gives me an idea whether or not I need to repeat the Sweet's treatment.  If another treatment is required I repeat the application of Sweet's using a fresh, clean patch and the undersize jag.

When I’m done with the Sweet's, I use dry patches to remove as much Sweet's as possible, and then I follow with a patch wet with denatured alcohol to dilute and remove any remaining Sweet's.

Next, I repeat the wet brush procedure using Ed’s Red to help remove anything that the Sweet's may have loosened, but not totally removed.  This procedure also helps ensure that any remaining Sweets is removed from the corners of the rifling grooves.  Dry patches follow to remove loosened crud and excess solvent.

Next I use a clean patch wet with Ed’s Red on a full-size jag to swab the bore, leaving it slightly damp.  If I’ll shoot the rifle within the next few days, I’m done.  If I’m going to shoot it right away, I follow with a dry patch to remove excess solvent and then a .45 caliber bore mop (assuming a .308/.30-06 diameter chambering) to remove solvent from the chamber prior to firing.  If I’ll be putting the rifle away for some time I use a bore preservative.

In this case, the dry patch that followed the Sweet's treatment did not show a great deal of blue, so I assumed that the new barrel was not collecting a lot of copper fouling.  That is unusual for a new bore, but this one did come from Kimber’s custom shop, so who knows?

I’d been adjusting the scope during the first three rounds, so I fired three more rounds to see how the new barrel would group. Nothing outstanding, but then I hadn’t had an opportunity to work up a load for this barrel yet.

I cleaned the rifle again after shooting the group.  Again, the dry patch that followed the Sweet's didn’t seem to show a lot of blue.

Upon returning to the house I pulled out the borescope to have a look.  Most of the barrel looked pretty good, but there was a section near the center of the barrel that showed some remaining copper fouling.  I got out the JB and scrubbed it thoroughly.  I used the borescope again after the JB was patched out and was shocked to find there was still a bit of copper fouling.  I decided to do a good brushing and then used patches to clean the loose gunk out.  Back to the borescope and the copper was gone.  It appears there was some machine chatter from some of the machinery that was used to make the bore.  The rough spots weren’t real big, but they were rough.  I planned to keep cleaning and using the JB to see if they would eventually smooth out enough to quit gathering copper.

Now if I hadn't had the borescope I'd have had no clue about the rough spots.  The copper fouling wasn't significant enough to give me very much blue on the Sweet's patches.  I wonder how many of my other rifle barrels have something similar??  I thanked my wife again for the birthday gift of that borescope.  I'm really enjoying being able to actually see the results of my cleaning.

On my next trip to the range I only fired three rounds from the rifle and waited to clean until I got home.  After using the Sweet's and removing it with the dry patches and denatured alcohol patches I checked the bore with the borescope.  There were a couple of spots with very small amounts of copper left, but nothing that a little brushing wouldn't probably have removed.  I elected to use the JB again because I wanted to take the opportunity to polish the bore up a bit more.

After a few passes with JB I patched as much JB out as I could and then brushed the bore again to help get it out of the crevices.  More dry patches followed and then some patches wet with Ed's Red.  Upon checking the bore with the borescope it looked pretty good.

Since the barrel seemed to be cleaning up fairly well, on my next trip to the range, I fired two different three-shot groups.  This was the first time I’d fired more than three rounds through the barrel without cleaning.  I used the full cleaning regimen after this session, but skipped the JB Paste as the barrel had seemed to clean up pretty well without the need for additional polishing. I went back to firing only one three-round group at the next range session.  Cleaning was again accomplished back at the house.  After a couple of patches with Ed's Red, I used the bronze brush (dipped in Ed's Red) and a couple of more dry patches to patch out the loose crud.  Then I used a patch wet with denatured alcohol to get the Ed's Red out, followed by one more dry patch. 

At this point I pulled out the borescope to have a look.  I was pleasantly surprised to find there was not a great deal of copper visible.  There were several relatively small streaks on the lands, most of that in the forward section of the barrel.  The farther back in the barrel I got, the better it looked.

I couldn't find a trace of what had once appeared to be machine chatter in the center of the barrel.  I guess part of my problem is that I'm not used to using a borescope and sometimes don't know exactly how significant something really is.  If the few rounds I've fired through this barrel have already smoothed out what I took to be machine chatter then it couldn't have been very serious in the first place.

While the lands only showed a few streaks of copper, the grooves appeared fairly dark.  I'm assuming that was carbon fouling that wasn't getting completely cleaned out.  I decided to use JB instead of Sweet's.  After multiple passes with the JB and several clean patches to get the JB out, I once again looked through the borescope.  The grooves were now much cleaner, but I was shocked to still find some traces of copper on the lands.  Apparently those spots were a bit thicker than I'd thought.

I used Sweet's as described above.  Ah, the Sweet's did its usual fine job.  No more copper in that barrel.  I followed up the Sweet's with a patch wet with denatured alcohol and then gave the barrel another good brushing to remove any additional fouling caught in the corners after the JB treatment.

At this point I noted that the barrel looked darned fine, at least to my eye.  I'm sure that a benchrest-quality barrel maker would still see some negatives with his borescope, but at this point I was fairly pleased with how this barrel was cleaning up.

I'm REALLY enjoying the borescope.  Too bad I didn't buy one of these years ago.  It's really nice to KNOW what I'm doing with the cleaning stuff instead of just guessing about it.  An example of this is the JB treatment described above.  I'd have thought the JB job I did would have removed the apparently light copper fouling in this barrel.  Without the borescope I'd probably have assumed that it had, since no copper fouling was visible in the muzzle end after the JB.  However, farther back there were some remaining traces on some of the lands.

I fired four rounds during the next range session.  Cleaning was again done at the house.  I cleaned with Ed's Red and a bronze brush.  I wiped the loose crud out with dry patches and then used a patch wet with denatured alcohol to clean out the Ed's Red.

When I looked down the bore with the borescope there was very little copper residue anywhere.  There were a couple of spots on the lands where there were traces of copper.  I decided to use Shooter's Choice MC#7 to see what it would do.  I let the Shooter's Choice soak in the bore for a shade over 30 minutes, and then I cleaned it out and used a patch with denatured alcohol to remove any residual Shooter's Choice.

SURPRISE!  There was still copper fouling in the bore.  I can't be certain that the Shooter's Choice didn't remove any of the copper fouling, but I can be certain that there wasn't a whole lot of copper fouling to start with and that a fair amount of it remained on some of the lands.   

Six minutes with Sweet's and all traces of copper fouling were gone.  I used a denatured alcohol patch to wipe out the Sweet's and then used a bronze brush with Ed's Red to make sure I got all of the Sweets out of the corners of the grooves.  The barrel is quite clean now.

Based on the small amount of copper fouling after four rounds it looked like this barrel was breaking in very nicely.

In the previous couple of cleaning sessions I’d learned that JB doesn't do a very good job of cleaning out anything over a trace of copper fouling and that Shooter's Choice doesn't seem to do a very good job of cleaning out even a trace of copper fouling.  I suppose Shooter's Choice might get more fouling if it was allowed to sit longer.  That will likely remain an unknown as I don't know if I have the patience to wait a whole lot more than half an hour.

I fired a five-shot group during the next range session.  Upon returning home I cleaned the rifle, following my standard cleaning procedure, but before I applied the Sweet's, I used the borescope and could not find even a trace of copper fouling in the bore!!!!!  WOW!!

The lands were completely clean, except for minor machining marks that seemed to contain a bit of carbon fouling.  The grooves were a bit dark, presumably with carbon fouling, but I couldn't find a trace of copper fouling.  I wet-brushed the bore again to see if I could get some more of the carbon fouling out, but I'm MOST IMPRESSED by the total absence of copper fouling.  The last round today was the twenty-seventh round fired through this barrel since I got it back from Kimber, and the thirty-fourth overall.  It appears to have broken in VERY QUICKLY.

I just finished cleaning the rifle after yet another five-shot group.  Again I looked through the borescope before using Sweet's.  The bore looked pretty good, but there were very minor traces of jacket fouling on some of the lands within the first few inches behind the muzzle.  It should be noted that prior to having the borescope, my standard check for copper fouling was to shine a Maglight flashlight into the bore at an angle from the muzzle end.  If I can detect copper there I take appropriate action to remove copper from the entire bore.  Utilizing that technique in this case, there is no detectable copper fouling near the muzzle.  The borescope shows that, while there isn’t much, there is indeed some copper fouling present.

The Sweet's took care of the scant amount of copper fouling in short order and a follow-on brushing removed some more crud.  The bore now looks quite good again, thank you.

Some might ask if it is necessary to follow a break in procedure in order to have a rifle that will be accurate enough for their purposes.  Since a good many rifle users do not break in their barrels, and still find them accurate enough, I’d have to say that it is not necessary.  However, in going through this cleaning regimen, it was quite obvious how quickly the amount of copper fouling from a given number of rounds was reduced.  Is that really important?  I don’t think I’m qualified to answer that question.  I’m fussy about my rifles and to my way of thinking it is worth it, but we each have our own priorities and your mileage may vary.



DaleMullin



Uploaded: 5/14/2005