Barrel Break In Observations

[rifleman700]

I was not sure where to put this thread so I decided to put it where the gunsmiths go.

I had an opportunity awhile back to break in three different barrels at the same time and then will do another one soon. Of the four barrels, they were from three different manufacturers and 20 years in manufacturing. I was really surprised at what the results were. I know this is a very small sample and if the sample of each barrel was increased I would probably have different results. My results in no way suggest that one barrel is of better quality than the other because they all shoot very well - well under half moa.

Let me say real briefly that I do not want this to turn into a big debate about whether barrel break in is necessary. So please lets keep comments civil if on that subject if possible. It is just an observation of each of the barrels and I wanted another perspective on what I saw. I WANT TO TALK BARREL QUALITY AND WHAT MAKES A GREAT BARREL.

There are many ideas when it comes to barrel break in especially when it comes to custom barrels. Over the years I have tried many different procedures and have had mostly good results. The only one that I did not have good results with was a Shilen Select Match RR HV that I chambered in 243W. With this one I just went to shooting and it took I would guess - its been awhile, close to 250 rounds to settle down and shoot. It was a real chore to clean that first 250ish rounds. This last December I set the barrel back after 3700 rounds fired and it now has a new shiny throat. The throat at that time had grown almost .200" and with the original chambering being a saami spec chamber the light bullets already had a mile jump with the 14 twist barrel. ( this was my first solo build and I knew very little about throating ) For me I see the biggest benefit of barrel break in is in cleaning and getting to the final load / barrel speed quicker in load development. I do have a throat maintenance process for overbore cartridges where I keep the throat polished and I know for a fact it works.

Ok, here are the details of each. Keep in mind these are hunting rifles first and foremost.

Rifle #1 was a Rem700 built be Lester Bruno chambered in 7RUM with a 26" Krieger #3.5 contour barrel. Break in loads were a moderate charge of Retumbo with 190 grain Matrix bullets.

Rifle #2 was a Rem700 built be Gre'tan Rifles chambered in 7SAUM with a 25" Bartlein #3 contour 5R barrel. Break in loads were a moderate load of RL26 with 168 Nosler LRAB bullets.

Rifle #3 was a Savage Model 11 LWH. This rifle never shot at all with the factory barrel. I had planned on buying the tools and installing the barrel myself but when I called Shilen to order barrel they offered to fit it. The 6.5CM barrel is a 22" Select Match S2 contour. Break in loads were factory 140 Hornady Amax loads that I got with rifle from the seller.

The process I am currently using for barrel break in is basically the Gre'tan Rifles method. This method has you start by cleaning barrel to the bare metal and then apply Daag 156 to bore. Fire one shot and then clean rifle to the bare metal again and reapply the Daag 156. The Daag 156 is said to fill the micro cracks left by any machining or flaws in the barrel and increases the burnishing process. Directions say a minimum of 10 shots with 20 being better. I have modified this number by what I am seeing in the cleaning process. I still do 20 rounds but not all one shot and clean.

My cleaning solvents for powder fouling are KG-1 and or C4. My solvents for copper are CU+2 and or KG-12. I find them all to be excellent. There are plenty of others that work but these are the best IMO. I use a punch type Bore Tech Proof Positive Jag for patches and Iosso Eliminator brush for powder and BT Proof Positive brushes for copper. Dewey rods are what I use the most of along with a caliber specific o-ring rod guide.

My first thoughts were that the 7RUM would break in quicker because it has the bullet with the most bearing surface so more burnishing is taking place and I figured the 6.5 CM would take the longest for the same reasons - with less bearing surface. I did wonder if the button rifled Shilen SM would break in differently but was not sure being they have all been lapped.

So I clean all of the rifles and then go outside and shot them all into my bullet catch. I go in and start cleaning. For the first three rounds the only thing that was obvious was that the shilen barrel was much easier and quicker to clean. At about round seven the Shilen barrel was taking only a few patches to clean both powder and copper. The Krieger and Bartlein were getting easier but had a long ways to go. At round eight I started shooting three rounds through the Shilen and it was still cleaning easier and quicker than the other two with only one round being shot through them. I would shoot the two cut rifle barrels by themselves until I caught to the round count on the Shilen so I could clean them all side by side so I could see the difference. By round twelve the two cut rifle barrels starting cleaning up nicely but still not quite even with the Shilen. By round 15 the two cut rifle barrels were where the Shilen was at round ten. By round 20 all barrels were too close to compare and cleaned up nicely.

Load work up for all of these was fairly quick and easy. Each barrel speeded up around 60-75 rounds not including the break in rounds.

I mentioned a fourth rifle in the beginning and I will be evaluating it shortly. This one is definitely a apples oranges comparison but I will post anything I see different. Its a 22BR with a Shilen SM barrel with rifle built by Shilen in the mid 90's. I bought it here on this site and the owner said it only had 20 rounds of hBN coated bullets through it. Inspection showed the bore to be dirty but it cleaned up with just a couple of patches with no copper seen and the throat looks fresh.

I have since discussed this break in comparison with a couple of gunsmiths and they both questioned whether the Shilen's barrel life will be shorter from what I was seeing. My only comparison is the 243W barrel mentioned above, but that barrel was bought and installed almost 17 years ago so not a good comparison plus it is still humming right along. Neither one seemed to think that the cut rifle vs. button had any significance in the results but I do.

Has anyone else had a similar experience with button and cut rifled barrels? I have only been using cut rifled for the past 10 years so this was kind of eye opening and maybe its normal and means nothing.

 

[Hoodoo]

Well that doesn't make any sense, I thought a guy could only get Cut rifled barrels to shoot well these days

 

[butchlambert]

Barrel break in? Sir, what are you trying to break in? Have you perused this forum to see all of the rhetoric?

 

[eddief]

IMHO this proves nothing because some reamers will produce a nicer throat and leade than another. I believe this has the biggest effect on how a barrel "breaks in".

 

[rifleman700]

IMHO this proves nothing because some reamers will produce a nicer throat and leade than another. I believe this has the biggest effect on how a barrel "breaks in".

So you are saying the finish of the throat affects barrel break in and there is no other part of the bore that needs burnishing? I believe that to a point but I think the barrel still needs burnishing / seasoning as most all metals do. I understand the need for a good smooth transition and throat area but I don't see how this relates to the rest of the barrel other than to say it doesn't need it. I assume you are also stating that when the barrel speeds up this is when the throat is broke in and burnished? If the throat was rough to begin with I would think this would create higher pressures and furthermore higher velocities. And this also brings up the question as to why do I see velocities increase and then level off once a certain amount of bullets are fired through the bore? If the barrel is smoother after break in you would think that the velocities/pressures would be lower unless the barrel is actually roughening up in the burnishing process possibly?

Also, as I understand it and I may be wrong but you have the chamber, a small transition from the neck to the leade and then the throat and the only area that affects the bullet travel is the throat. The leade is .0005" larger than the bullet diameter and would not be part of the metal being affected.

 

[Ggmac]

I'm sorry , I wasn't going to even respond but , I agree with all other posters . A hand lapped barrel needs no break in , the chamber that has cut the 1 deg 30 leade throat , whatever you call it , needs the break in .
It's possible the barrel vel increase is due to chemical ( gliding metal , powder gases , pressure and temp chemical deposits . I'm not really sure about the vel increase as it doesn't seem to happen on all barrels .
Unless your calling barrel break in the vel increase , I still assert that the only part of a barrel that needs to be ' broke in ' is the chamber cutting process .
It would be great to due a test on a hammer forged barrel that also hammers the chamber in and compare .
I've been chamberings barrels since I was 18 , I'm retired now , I've test more theories than I care to mention . Testing and trying ' new ' ideas have yielded little . The positive experiments I've tested have been helpful , the failures are many ( shooting with the barrel in a vacuum ) thinking velocity would be huge and wear non existent . Huge failure . One of many , but that's how we learn , I try to stay open minded and still want to learn .
Don't stop , if I've done anything I hope it encourages a further test .

 

[butchlambert]

Listen to what eddief and Ggmac are saying. You mentioned only custom barrels. It has been many many years since I've shot a factory or hammer forged barrel. I can't comment on them.

 

[hpshooter]

" the failures are many ( shooting with the barrel in a vacuum ) thinking velocity would be huge and wear non existent . Huge failure . One of many , but that's how we learn , I try to stay open minded and still want to learn .
Don't stop , if I've done anything I hope it encourages a further test "

Well, you aren't the only one that ever had that thought although you did have the where with all to actually try it. Was never able to access a vacuum pump large enough to do what I had in mind. Wanted to attach a 4 cuft. chamber to the muzzle evacuate it and collect the gas from the powder burn before the projectile exited the chamber through a rubber diaphragm. Made sense when I was 16 and had all the knowledge in the world!

 

[eddief]

I think it's great you are testing and experimenting, but in the case of a custom barrel that was lapped correctly and the bore/groove dimensions are what they should be, the bore is as good as it's going to get in my opinion. You are breaking in the freshly machined throat/leade.

You can deburr/break in a new leade before shooting if it needs it, but that has been discussed before too. Search and google are your friends.

 

[rifleman700]

So the .014" throat is creating all of the powder and copper fouling to occur?

What about copper fouling I can physically see at the muzzle end that diminishes as the barrel shoots in?

And what is the answer to velocity increase as no one seems to have a reason for this? And if you are not seeing it then you are not measuring it. And I say this because I do have a large sample when it does come to this and has been evident in every sample with no difference when it comes to barrel types or manufacturers in custom barrels.

Thank you all for your input. It is always enlightening to get another perspective on something like this.

 

[Ggmac]

So the .014" throat is creating all of the powder and copper fouling to occur?

What about copper fouling I can physically see at the muzzle end that diminishes as the barrel shoots in?

And what is the answer to velocity increase as no one seems to have a reason for this? And if you are not seeing it then you are not measuring it. And I say this because I do have a large sample when it does come to this and has been evident in every sample with no difference when it comes to barrel types or manufacturers in custom barrels.

Thank you all for your input. It is always enlightening to get another perspective on something like this.

Copper 'fouling ' at end of barrel has been proven that it's the copper jacket material that has been atomized ( lack of better word , no coffee yet ) by the blow by in the discharge of bullet from case and the copper in gas suspension is cooling and being deposited on the cooler part of the barrel .
Now I know the next question is PROVED BY WHO ? Well to answer that I'd have to retread about 20-30 books , articles and will take some time .

 

[oliver88]

BREAK-IN


With any premium barrel that has been lapped, the lay or direction of the finish is in the direction of the bullet travel, so fouling is minimal. This is true of any properly finish-lapped barrel regardless of how it is rifled. If it is not finish-lapped, there will be reamer marks left in the bore that are directly across the direction of the bullet travel. This occurs even in a button-rifled barrel as the button cannot completely iron out these reamer marks.


Because the lay of the finish is in the direction of the bullet travel, very little is done to the bore during break-in but the throat is another story. When your barrel is chambered, there may be reamer marks left in the throat that are across the lands,i.e. across the direction of the bullet travel.When the bullet is forced into the throat, copper dust is released into the gas, which at this temperature and pressure is actually plasma. The copper dust is vaporized in this gas and is carried down the barrel. As the gas expands and cools, the copper comes out of suspension and is deposited in the bore. This makes it appear as if the source of the fouling is the bore and subsequent bullets and deposits are fired over it: Copper, which adheres well to itself, will build up quickly and may be difficult to remove later. So when we break in a barrel, our goal is to get the throat polished without, allowing copper to build up in the bore. This is the reasoning for the "fire-one-shot-and-clean" procedure.


Barrels will vary slightly in how many rounds they take to break in because of things like slightly different machinability of the steel, or steel chemistry or the condition of the chambering reamer, ect... For example a chrome moly barrel may take longer to break in than stainless steel because it is more abrasion resistant even though it is the same hardness. Also chrome moly has a little more of an affinity for copper than stainless steel so it will usually show a little more "color" if you are using a chemical cleaner. (Chrome moly and stainless steel are different materials with somethings in common and others different.) Rim Fire barrels can take an extremely long time to break in - - - sometimes requiring several hundred rounds or more. But cleaning can be lengthened to every 25-50 rounds. The break-in procedure and the clearing procedure are really the same except for the frequency. Remember the goal is to get or keep the barrel clean while polishing out the throat.


Finally, the best way to break-in the barrel is to observe when the barrel is broken in: i.e when the fouling is reduced. This is better than some set number of cycles of "shoot and clean" as many owners report practically no fouling after the first few shots, and more break-in would be pointless. Conversely, if more is required, a set number would not address that either. Besides, cleaning is not a completely benign procedure so it should be done carefully and no more than necessary.


It is a good idea to just observe what the barrel is telling you with its fouling pattern. But once it is broken in, there is no need to continue breaking it in.


Initially you should perform the shoot-one-shot-and-clean cycle for five cycles. If fouling hasn't reduced, fire five more cycles and so on until fouling begins to drop off. At that point shoot three shots before cleaning and observe. If fouling is reduced, fire five shots before cleaning. It is interesting to shoot groups during the three and five shot cycles.

 

[scubohuntr]

Was never able to access a vacuum pump large enough to do what I had in mind. Wanted to attach a 4 cuft. chamber to the muzzle evacuate it and collect the gas from the powder burn before the projectile exited the chamber through a rubber diaphragm.

Would be interesting data, if it worked. It would take a pretty impressive diaphragm to hold, even in .224, against any type of vacuum and still be bullet-permeable. I also don't think you would get an airtight seal at the chamber end, although you could probably rig a silicone gasket around the extractor groove and single shot it. For most accuracy-loaded ammunition with relatively low neck tension, it's got some potential as a bullet puller, though. Hmmm... automotive hand vacuum pump, short smooth bore, short chamber with a couple of O-rings, an elbow to keep pulled bullets out of the pump... Easier on bullets than a collet. Probably wouldn't work with crimps.

 

[rifleman700]

Some good stuff here that I will have to research further. My first reaction to the powdered copper theory was I did not buy it because if it was powdered material it would not need the amount of attention that it is requiring to get it out. And I am only seeing copper in the rifling at the muzzle end. This theory seems to have some merit but there are gaps that say otherwise but I will keep an open mind and research this further.

No answer yet though on velocity increase. This seems to be something that nobody can answer or that some will not even acknowledge for whatever reason.

 

[gunsandgunsmithing]

No answer yet though on velocity increase. This seems to be something that nobody can answer or that some will not even acknowledge for whatever reason.

What chronograph and did temps go up while you were doing the testing? Lighting conditions can affect many chronographs and temps affect all loads.

 

[wholman]

Did you use the same powder in all of these test guns.

 

[Ggmac]

Would be interesting data, if it worked. It would take a pretty impressive diaphragm to hold, even in .224, against any type of vacuum and still be bullet-permeable. I also don't think you would get an airtight seal at the chamber end, although you could probably rig a silicone gasket around the extractor groove and single shot it. For most accuracy-loaded ammunition with relatively low neck tension, it's got some potential as a bullet puller, though. Hmmm... automotive hand vacuum pump, short smooth bore, short chamber with a couple of O-rings, an elbow to keep pulled bullets out of the pump... Easier on bullets than a collet. Probably wouldn't work with crimps.

I was able to get a good repeatable seal , I started using a rimmed case , no extractor , small cut in chamber for an o ring . Then tried 38 special .
Problem at the time was $$$$and time and chrono problems .
I should have the papers around here somewhere . I think .

 

[Ggmac]

Some good stuff here that I will have to research further. My first reaction to the powdered copper theory was I did not buy it because if it was powdered material it would not need the amount of attention that it is requiring to get it out. And I am only seeing copper in the rifling at the muzzle end. This theory seems to have some merit but there are gaps that say otherwise but I will keep an open mind and research this further.

No answer yet though on velocity increase. This seems to be something that nobody can answer or that some will not even acknowledge for whatever reason.

I think I can explain the copper in rifling , here goes , just having coffee so memory is slow .
The copper in suspension is blown ahead of the bullet and deposited ( plating the interior ) then as the bullet passes , it irons ( lack of post coffee word ) in the plating and removes some usually leaving the copper in the bore . I'll try to find where I read that .
More coffee ....

 

[rifleman700]

What chronograph and did temps go up while you were doing the testing? Lighting conditions can affect many chronographs and temps affect all loads.

I use either a Oehler 43 PBL or a Oehler 35. I have modified both with a side wall of sorts to allow for different lighting conditions.

For my personal load development I record all conditions from each range session. With the temperature function in Quickload I can get fairly accurate results with the changing conditions once the burn rate is adjusted and correct. Load development I do for others I give them the final load data and what they can expect to see in differing temperatures. I try to mirror the conditions in what they will be shooting in.

 

[rifleman700]

Did you use the same powder in all of these test guns.

No. Different powders, rifles, barrels, cartridges, temperatures etc. One constant was that each barrel sped up after a certain amount of time and then leveled off. And the point at which each barrel sped up was never at a set number of rounds. Off the top of my head I would say between 50-150 rounds is where the barrel would settle in at its final velocity. Depending on the cartridge and how hot the load is I usually don't see any velocity change for several hundred rounds after this, maybe 300-500 depending throat wear and resultant pressure / velocity drop. I try to keep my throats polished on my larger capacity cartridges to keep from having to chase lands and tweak loads.