Barrel chamber scratches

I finished a couple of new barrels---22-250---and have shot both a few times, both
appeared to be good shooters.

In the meanwhile I bought a Lyman bore scope and have found scratches in both
barrels-----top of the lands in the throat area----only.

I originally thought this had occurred when reaming the chambers but now am pretty
much convinced I did it twirling a bore brush to clean out in front of the chamber neck.

I have another barrel which will be rechambered so I decided to repeat the twirling on this chamber.
Scratched it also----convinced me that I caused the problem with a bronze bore brush. I don't have time to spend figuring how bronze will scratch stainless-----just want to move on to the correction
of this problem.

I'm sure I can remove these scratches by reaming the chamber a bit deeper----and correcting the tenon and headspace. This wouldn't be new to me but I'd like to avoid, if possible, the extra work.

Anybody here have an easier solution for this ?

Will appreciate any ideas on this.

A. Weldy

 

You think you scratched the barrel with a bronze brush humm.

 

I'm depending on logic for my suspicions.

The sacrificial chamber didn't show any such scratches before
twirling the brush----showed scratches after.

I'm surprised at this but its all I can conclude.

At this point I just want get out of this situation and figure how it
happened later. Just looking for other ideas to remedy this.

A. Weldy

 

Did you twirl this brush by hand or on a drill just curious.

 

By hand.

 

Why do you want to get rid of the scratches?

 

Get a refund on the borescope, buy more bullets and have fun. Mike

 

Did you use range rods to indicate the barrel, they can scratch the top of the lands if you don’t smooth the ends of the bushings.

 

Doug, I have no such experience to guide me but am concerned that the scratches
will cause more copper fouling----just a suspicion on my part.

Mike, I wish I could get comfortable with your approach----not looking forward
to putting two barrels back in the lathe.

Spotshooter, I indicated in the estimated throat with a Grizzly Rod, followed by a long stem indicator.
The pilot bushing was checked with a magnifying glass with no sign of rough spots.

On both barrels, these scratches were on the sloped portion of the throat.

Have considered shooting both barrels to check for excessive copper fouling.

A. Weldy

 

Should be no news that a bronze brush will scratch. Wilson Combat sells bronze chamber brushes in pistol calibers that are intended for quick and dirty keep it working as cleaning the chamber over lunch during a high to very high round count training session. The Wilson Combat brushes have a reputation for very visible scratches but that can be what it takes to keep up with high round count exercises on the square range or down range when rushed. As to how, it's not impossible to polish a diamond but the polishing compound is worn away faster than the harder diamond. Then again it's perfectly possible to polish a chamber, Zediker goes into it for gas guns and J.B. compounds are useful for cleaning, polishing and even for hard fitting. Then again one of the MacMillan family was death on J.B. in his barrels. There are those who suggest breaking in a barrel by rolling a bullet in grit. Myself if I were really worried I'd probably get the barrel really clean, easier now than later, and apply a ceramic bore coating. Properly applied and cured the ceramic bore coatings go a long time between bore cleanings. Then again I might coat one barrel and shoot the other just to see.

 

Does that Lyman borescope have a little screen that you can see the scratches if so would be nice to see pictures of your issue I think you would get better answers to your concern of what your seeing.

 

Here's a shot of all four land tops in the throat in one barrel.

Sorry, pictures didn't work.









A. Weldy

 

Shoot it ten times and clean and recheck.

 

Here is pics of Lucky Shooters throat definitely not from a bronze brush have it it guys I think a dull reamer at the throat unless chamber rpms is a factor may be wrong.

 

Scratches may be a bit extreme. Slight blemishes is more appropriate. For 40+ years I've used nothing but brass brushes and clean frequently. I've never hurt a barrel. After about 300 rounds I intentionally twist my brass bore brush in the neck/throat area to manage the carbon build up at the end of the neck. Never lost a minutes sleep over it.
Take a polished piece of barrel and run the brush over it. Marks yes, scratches not really. They will disappear in just a few rounds.

 

I'd have to go with a dull reamer along with a possible poor fitting pilot.

 

Yep reamer marks. probably dull, could be feed rate, could be chip load, could be lubrication.
Could be all the above.

 

Dave and stan have the answer above. Check that reamer. If youre manually oiling the reamer and cleaning it (not flush system) take shorter passes on the last 1/4” or so. Clean the reamer more often.

 

I let Lucky Shooter borrow my brand new reamer. RPM he used was 70. Dark sulphur cutting fluid.

I have never seen this in one of my chambers...mind blower for sure.

 

Chips do damage like that- not necessarily the reamer