Excessive copper fouling

[sodak]

My friend recently bought a FN Win Mod 70 in 300 wm. He has been getting excessive copper fouling starting 4 inches from the chamber and continuing to the muzzle. The LGS borescoped the barrel and couldn't find any rough spots but commented on how it was wierd for copper to be building throughout the barrel. My friend then fire lapped the barrel. After firelapping cleaning was easier but the copper fouling will still build up after 10 shots (of factory 180gr Win powerpoint ammo).

This rifle has been back to FN 2x. The second time they didn't even send back a report. My next suggestion was to slug the barrel and measure diameters to see if it has too narrow of a bore diameter. I haven't seen where he fired over a chrony to see how velocities are comparing to my 300wm (same barrel legnths).

Has anyone else seen this?

 

[Guy Miner]

The only real excessive fouling I've seen was with all-copper Barnes bullets.

Some bores do foul more easily than others. Particularly rough factory barrels. I'm not surprised that the fouling extends from the chamber forward. A lot of times the rough area in the throat is where the jacket material starts getting scrubbed off the bullet. Then it gets smeared through the rest of the barrel. Often without a bore scope, all we see is the fouling near the muzzle.

What did he fire lap it with?

I'm thinking a good bout of hand-lapping with some JB bore paste should clean that thing up pretty well. Have done that myself with good results. I've heard of good results also from a product called ultra bore coat - but have never used it myself. It's supposed to dramatically reduce fouling.

Or... it's a great excuse to order up a custom hand-lapped Krieger, Lilja or other custom barrel... :grin:

 

[chet]

How much copper fouling are we talking here? ANY barrel will have copper in it after ten shots.

was the barrel broke in properly? Sometimes a rifle needs more than 10 or 15 break in shots. The last Kimber I broke-in took nearly 40 (shoot one/clean), before copper noticeably lessened.

Also, I've noticed that the winchester power points are quite generous with their copper deposits.

I don't care for fire-lapping, it erodes the throat. And beyond the throat, it does little more than a regular bullet.

Try a different bullet/load. Clean with JB paste. The paste will smooth things out in a hurry.

 

[Guest]

I'm curious how much fouling he's getting, as well. The real question is, how does it shoot overall? Does it go from .5" for the first five shots to 5" for everything after ten shots, or does it shoot reasonably (<1.5") even with the fouling? If he's losing accuracy, it's an issue. If he's not, tell him to relax.

Speaking from experience, short-stroking JB's bore paste will help a lot, but it's an arduous and time consuming process if he's not losing accuracy. If he follows te directions for JB's and really works it through the bore, it will cut down on fouling. He may just need to relax, though. Ad shoot something other than power points. They do foul more.

 

[JD338]

I'm curious how much fouling he's getting, as well. The real question is, how does it shoot overall? Does it go from .5" for the first five shots to 5" for everything after ten shots, or does it shoot reasonably (<1.5") even with the fouling? If he's losing accuracy, it's an issue. If he's not, tell him to relax.

Speaking from experience, short-stroking JB's bore paste will help a lot, but it's an arduous and time consuming process if he's not losing accuracy. If he follows te directions for JB's and really works it through the bore, it will cut down on fouling. He may just need to relax, though. Ad shoot something other than power points. They do foul more.

+1 to what dubyam said.

JD338

 

[sodak]

The barrel was broken in by shooting one and then cleaning for 10 shots, then shoot 3 and clean for 9 shots, then shoot 5 and clean for 20 shots. In total ~100 rounds so far has been fired through this barrel. The problem was noticed after shooting the 5 shot strings and has continued. Fire lapping was then done. After a few more 5 shot strings rifle was sent to factory where it looked like they cleaned it and sent it back saying that all was 'in spec'. After shooting 10 rounds at range excessive copper fouling remained where rifle was sent back to factory.

The rifle will shoot ~MOA with a 5 shot string and then will groups will open to 1.5in and continue to open if the barrel is not cleaned. Multiple handloads have been used with multiple bullets and powders.

The bore was scoped at the LGS by a gunsmith. They could not see any defects (but there are limits to the human eye). That is why this rifle has been back to the factory 2x. I do not consider this to be taken as 'all rifles gain copper fouling'. This is a problem. Luckily the LGS here stands behind their sales and has offered a trade-in. If you wish to busisness with them they are First Stop Guns in Rapid City, SD. I think they deserve a plug for their service in this situitation.

If you read the initial posts my recommendation was to shoot over a chrony and have some numbers to support the visual problem. Also to slug the barrel and measure against the tolerances to see if the rifle is not 'in spec' as the factory claims.

 

[chet]

I think at this point I'd slug the barrel.
Slug the muzzle end, then push it back. If it gets harder to push as it nears the chamber, then the barrel got put on backwards. If one end of the barrel is tighter than the other, the manufacture always puts the tight end on the muzzle.

questions:
How much cool down time was between the 5 shot strings?
How much cool down time was between each shot?

Throats on 300 mags get HOT! and this heat can cause copper fouling in this area.

What other bullets has he tried? IMHO, ballistic tips of the "hunting" variety are one of the best bullets for minimum copper fouling.

Velocity can be a factor in fouling, but he's probably around 3000fps and I don't see that being a problem.

the shoot one/clean one for ten rounds is just a rule of thumb, I've had some rifles improve drastically with just 5 steps, some need 40+. Remember, if you don't get all the copper out between shots, you're just wasting time.

I know this is frustrating, just trying to throw some ideas at ya :grin:

 

[chet]

On second thought....... If the clean gun will shoot 5 shots @MOA then lose accuracy from that point as fouling increases, then it really just needs more break in. (assuming cool down times are sufficient)
Start the break in over, and be sure ALL copper is removed between each shot.
shoot one/clean for 20 shots, then shoot your groups and I bet you'll be tickled.
IMO each barrel will require a little modification to standard break in procedures.

8)

 

[Antelope_Sniper]

SoDak, what bullet at what velocity?