300 WSM & 7 SAUM rate of increased MV??

[DenisA]

Thought I'd add another update.

Of course David was right regarding carbon fouling.

This barrel has still been speeding up and it now has 880 rounds through it. I had to drop the powder to 62.7gn and recently it needed another drop.

I haven't wanted to run a polish through the bore up until now incase it affected the accuracy, but since the powder charge is getting close to the recommended minimum I thought it was time. It wasn't until I started polishing the bore and inspecting it with the bore scope that I have realised how much of that ceramic type carbon build up is actually in there. Using a courser paste I gave it a thorough polish including short stroking the throat. I removed some carbon, but there's still plenty left. In fear of taking too much metal out I thought I'd leave it there and run some rounds through the Magnetospeed. Over 16 rounds, the average MV has dropped by 70fps.
Considering there's still a lot of that hard ceramic type carbon in there I believe that must be the cause of the MV increasing.

I said in the original post that the barrel cleanliness was well maintained. By that I meant that I cleaned it regularly, until no copper or powder was seen on the patches. The same way that I look after my 6BR and .284W barrels that don't share the same grievance.
Admittedly, I don't like to clean through the course of a PM and have never had this big of a carbon issue with the other cartridges.

I think it must come down to string shooting a cartridge that has a large amount of powder (originally 67gn for a low node). Also I think AR2213sc is a fairly dirty powder. I think I might have to bring this bore back to metal and run some polish through it every clean, but I'm not sure how long you can get away with that before the bore opens up too much and loses accuracy.

I'm considering molly coating bullets but based on the threads that I searched and read on this forum, the consensus is that molly doesn't stop that hard baked carbon................ does it?

I'm also wondering if AR2217 burns cleaner than AR2213sc. Does anyone have experience there?

[DenisA]

When I started shooting the 300WSM years ago, trying to get the 230's and 215's going, I had a lot of trouble. In load development at the short range they were SENSATIONAL but I couldn't get consistently competitive scores or consistently good vertical at the longs with them.
All sorts of theories came to mind and threads were posted and answered. Anyway, now I'm wondering if it was just that the barrel kept carboning up, speeding up and I wasn't aware of it. The introduction of highly portable and easily setup chronographs such as Magnetospeeds has really changed how careful and precise we can be with loading.

[Steve N]

Denis did you see a build up of carbon in the corners of the rifling? Is the carbon build up the entire length of the barrel? I have used pastes whenever needed and doubt that JB non imbedding bore paste will do any damaged if used carefully. Keith Hills has recommended removing carbon by heating the barrel by pouring a litre of boiling water through it then carby cleaner with bronze brush. Might take quite a bit of work but it does remove carbon.
Steve.

[KHGS]

Denis did you see a build up of carbon in the corners of the rifling? Is the carbon build up the entire length of the barrel? I have used pastes whenever needed and doubt that JB non imbedding bore paste will do any damaged if used carefully. Keith Hills has recommended removing carbon by heating the barrel by pouring a litre of boiling water through it then carby cleaner with bronze brush. Might take quite a bit of work but it does remove carbon.
Steve.

Ah, Ha, it's good to see that someone has listened to me about cleaning! As I have said on this forum many times, most shooters have little idea in barrel cleaning. Carbon is the real enemy, it is insidious & will sneak up on you. Copper fouling by itself is rarely a problem in well run in quality match barrels, but is more easily detected & often gets the blame when it is not the problem. I am sure what I have written is in the forum archives, I suggest those that are having "barrel" problems seek them out & reread my comments. If questions remain, ask & I will give an opinion.
Keith H.

[DenisA]

Denis did you see a build up of carbon in the corners of the rifling? Is the carbon build up the entire length of the barrel? I have used pastes whenever needed and doubt that JB non imbedding bore paste will do any damaged if used carefully. Keith Hills has recommended removing carbon by heating the barrel by pouring a litre of boiling water through it then carby cleaner with bronze brush. Might take quite a bit of work but it does remove carbon.
Steve.

Hi Steve. In the early stages I had seen carbon in the corners. I was only using nylon brushes at that stage too. I went back to bronze after David's advice. The baked carbon that I've allowed to build up now is on the flats of the lands and grooves too. It's actually a little deceiving because after a good clean it shines like polished steel and can be difficult to differentiate under the bright light that I use on the bore scope. I've realised that although more detail in the surface can be seen with a bright light, better contrast between steel and carbon is seen with a duller light.

[ecomeat]

Denis did you see a build up of carbon in the corners of the rifling? Is the carbon build up the entire length of the barrel? I have used pastes whenever needed and doubt that JB non imbedding bore paste will do any damaged if used carefully. Keith Hills has recommended removing carbon by heating the barrel by pouring a litre of boiling water through it then carby cleaner with bronze brush. Might take quite a bit of work but it does remove carbon.
Steve.

When I did the "barrel deal" with Macguru that saw me end up with his broken in , unloved 280AI barrel, as i mentioned elsewhere a borescope inspection revealed a lot of carbon.
I had also heard of Keith's boiling water & carby cleaner method, and that was the first thing that I tried. I had heard others speak of big pieces of carbon "curls" being removed, and was hoping to see something similar. Unfortunately for me, i had no such luck. I actually strained the water through a clean white sheet as it passed through the barrel, and there was barely any black or dirty residue at all....and certainly no big curls of carbon. After about 4 x 2 litre hot water jugs of boiling water, followed by lots of patches and bronze brushing , i gave up on that.I absolutely believe that it would work in some cases, but it didnt do a thing for Macguru's barrel.
I did mention that it was really dirty with carbon, didnt I ? . It was certainly baked on and had that nice "ceramic" sheen that you can see with a Hawkeye , after the carbon has decided that it wants t stay there forever
Next i tried a week long soak with "Patchout" using a bore plug, and topping up as required, followed by patches and bronze brushing. Still no visible removal of the carbon.
Then another week of Patchout soaking, followed by a bronze brush while still damp. Still looking at the same amount of carbon.
In the end it took a lot of elbow grease with an abrasive to get it out. I actually used Iosso paste, JB's and KG2 so cant really credit one particular product with the success. I was fairly cranky by this stage and just wanted the blody thing clean

[macguru]

And still it did not make any difference .... So maybe owning a borescope is a negative thing ?? I think you need to ask yourself WHY the carbon is bad ? I think the answer is that a carbon ring in the lands (and ridges?) can distort the jacket of the projectile. Surely at that point, a bronze brush would break up the raised carbon.

If it is so flat that you cant break it up, maybe its not the cause of the problem anyways ....

BTW where are those sharper photos ? I cant afford a borescope like some people ...

[DenisA]

Thanks for your experience Tony. I have the 2 JB pastes. I find them quite fine and haven't thought too much of their ability in removing heavy carbon in the past. They may be O.K for regular tidy up's though? AutoSol is excellent for heavy carbon fouling and certain it will get this bore clean. It will be a long frustrating process though.

I'd like to make a lead lap as David had posted about.

I'll also play with Keith's hot water recommendation. I have seen the effect of hot water in person, used by a club mate. After he had cleaned his barrel to the point that patches were clean, he was running hot water through the barrel and then just running dry patches through. The patches were coming out black.

It's a finicky game. Just when I think I have an aspect of it worked out another lesson bowls me over.

[DenisA]

And still it did not make any difference .... So maybe owning a borescope is a negative thing ?? I think you need to ask yourself WHY the carbon is bad ? I think the answer is that a carbon ring in the lands (and ridges?) can distort the jacket of the projectile. Surely at that point, a bronze brush would break up the raised carbon.

If it is so flat that you cant break it up, maybe its not the cause of the problem anyways ....

BTW where are those sharper photos ? I cant afford a borescope like some people ...

This whole thread is a testament to the negative effect of carbon and the positive to owning a borescope. Without being able to polish some carbon back to then actually see how thick it was, I wouldn't have known why this barrel keeps speeding up. It would be interesting to know what that's doing to chamber pressure. Probably a good thing I'm not string shooting a maximum load.

There has been no negative accuracy effect on this barrel other than constantly having to adjust its tune which is a negative in the course of a longer competition. Though I have heard it explained on this forum that heavy carbon build up in the first few inches, swages the bullet to a lesser O.D than the I.D of the remainder of the barrel. That can cause a poor seal, allow the bullet to rattle down the bore and probably allow the bullet to exit the muzzle at slightly different angles........ I guess??

[Julian D]

Very interesting read gents, I may have just found myself at that point.
We are lucky enough to have a club member who has a sonic cleaner that fits barrels, so he did mine last week & I have lost about 50fps.

It had a lot of carbon in the barrel & now it is cleaner than new....

After reading your posts on the subject it is all starting to make sense.

[DenisA]

Very interesting read gents, I may have just found myself at that point.
We are lucky enough to have a club member who has a sonic cleaner that fits barrels, so he did mine last week & I have lost about 50fps.

It had a lot of carbon in the barrel & now it is cleaner than new....

After reading your posts on the subject it is all starting to make sense.

Hi Julian, does that mean that ultra sonic cleaning a barrel has been proven to remove this stubborn carbon fouling? Cheers.

[Julian D]

Absolutely Denis, the longer he leaves it in the cleaner it gets it. He normally asks how clean you want it, last time he left a bit of carbon in it so I didn't have to run it in again, but we found a good build up this time about 4-6" from the chamber & I decided I wanted it spotless, I had to wear sunnies after I got it back..... it does a fantastic job.

He is a member on here & he might chime in from a more technical point of veiw. He also has a good hawkeye & is quite experienced in what to look for when looking down a barrel.

[KHGS]

And still it did not make any difference .... So maybe owning a borescope is a negative thing ?? I think you need to ask yourself WHY the carbon is bad ? I think the answer is that a carbon ring in the lands (and ridges?) can distort the jacket of the projectile. Surely at that point, a bronze brush would break up the raised carbon.

If it is so flat that you cant break it up, maybe its not the cause of the problem anyways ....

BTW where are those sharper photos ? I cant afford a borescope like some people ...

It is!!!!!!
Keith H.

[macguru]

But in Tony's case he cleaned this 7mm barrel to the nth degree and it still did not shoot. I still like my idea that the barrel went out of shape by a micron or so when it warmed up, thats what it looked like when i was shooting it, and Tony thinks that it was a badly cut land in the rifling but thats his idea

I totally agree that if you let a carbon ring build up it can open up your group though, I have seen that happen on my 6mm but after a good clean that particular barrel is winning stuff .... I now try to keep it clean !

BTW did anybody actually buy that lyman ultrasonic barrel cleaner ???? where and how much ??

[DenisA]

And still it did not make any difference .... So maybe owning a borescope is a negative thing ?? I think you need to ask yourself WHY the carbon is bad ? I think the answer is that a carbon ring in the lands (and ridges?) can distort the jacket of the projectile. Surely at that point, a bronze brush would break up the raised carbon.

If it is so flat that you cant break it up, maybe its not the cause of the problem anyways ....

BTW where are those sharper photos ? I cant afford a borescope like some people ...

It is!!!!!!
Keith H.

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