Strange whitish deposit in barrel - cause, solution"

[Snyper]

I recently started to see a significant degradation in repeatability in my five-month-old CZ 457 Varmint MTR (>1 MoA @ 50 yards). I bore scoped the barrel (which has around 2500 rounds downrange, has been religiously cleaned using Boretech C4 only) and saw a whitish hard deposit, this after a deep clean (24 hour soak of chamber in C4, dry patched , then C4 wet nylon brush down the chamber multiple times, dry patched again, then C4 wetted bronze brush, dry patched again, then a light oil wet patched/dry patched). Being a relatively new shooter (this is my first rifle), thought I would turn to the very experienced rimfire enthusiasts here to see if I could get your thoughts as to what is causing this and what I should do to remove it and get the barrel back to decent shooting condition. BTW, this deposit is around the chamber area and the first 4.5" of the barrel. Borescope screen shots from video are attached.

Thanks in advance for all your guidance and help - am getting quite frustrated since I can't find much on the web and have no idea what to do to remove this deposit.

Synper.

 

[John?]

Hard tk tell from those photos. My first guess would be lead and bullet lube buildup. I would hit it with a bronze brush and the lead remover solution of your choice.

 

[flogxal]

I'd guess C4 in the barrel, hitting the lead & lube, is making some minor salts from either the lead or the lube contents, and you are seeing salts+ deposits. Lead remover would be my call too.

 

[oldrifleman]

Yeah try some Rimfire blend, let it soak for a few minutes and brush it, run a RB patch through and repeat. I am betting you will see a big difference.

 

[Big Phish]

What ammo you are using? Is accuracy degraded lately?

 

[hafejd30]

It’s leading

My B14R has some as well. Rimfire blend won’t touch it

Here’s a photo for reference I found of an airgun when I was looking into mine a while back

 

[hafejd30]

Has anyone used this before?

 

[6.5SH]

Has anyone used this before?

View attachment 8724742

I have and it honestly doesn't do much.
JB blue or RemClean (40x/Gold Medallion, depending on the label) have been much more effective on something with a lot of fouling.

 

[JerkyFreak]

Also, screw the little mirror thing back onto the end of the borescope. Looking straight down the barrel makes it difficult to see the sides.

 

[JerkyFreak]

I might seem like a broken record, but ditch the nylon brush.

If you are going to brush, get Ballistol and the correct size phosphor-bronze brush. The bronze works realy well on lead and won't damage the steel, provided you do not use an abrasive cleaner; hence the Ballistol.

 

[John?]

Lead out works OK but it isn’t brushless by any stretch of imagination.

I use a Lewis Lead Remover to mechanically get rid of most fouling. It’s just a bronze mesh on a jag, so you could just wrap bronze wool around a worn bore brush. That’s what I do for odd calibers like 9.3x62.

Follow up with chemical cleaner and patches.

I tried Ballistol. It is a fine general purpose cleaner. As with all general purpose things, it isn’t great at most jobs. Diesel fuel is common on our farm and it works about as well for carbon removal.

 

[bobby1028]

I might seem like a broken record, but ditch the nylon brush.

If you are going to brush, get Ballistol and the correct size phosphor-bronze brush. The bronze works realy well on lead and won't damage the steel, provided you do not use an abrasive cleaner; hence the Ballistol.

^^^^. We treat these barrels like somebody's arteries. I still use bronze brushes and Hoppes...thousands of rounds and countless cleanings I've never seen accuracy degrade on my most expensive 22lr barrels. Nylon brushes and wet patches don't remove carbon rings or leading.

 

[Baron23]

I recently started to see a significant degradation in repeatability in my five-month-old CZ 457 Varmint MTR (>1 MoA @ 50 yards). I bore scoped the barrel (which has around 2500 rounds downrange, has been religiously cleaned using Boretech C4 only) and saw a whitish hard deposit, this after a deep clean (24 hour soak of chamber in C4, dry patched , then C4 wet nylon brush down the chamber multiple times, dry patched again, then C4 wetted bronze brush, dry patched again, then a light oil wet patched/dry patched). Being a relatively new shooter (this is my first rifle), thought I would turn to the very experienced rimfire enthusiasts here to see if I could get your thoughts as to what is causing this and what I should do to remove it and get the barrel back to decent shooting condition. BTW, this deposit is around the chamber area and the first 4.5" of the barrel. Borescope screen shots from video are attached.

Thanks in advance for all your guidance and help - am getting quite frustrated since I can't find much on the web and have no idea what to do to remove this deposit.

Synper.

Snyper - I'm not a rimfire guy but I have passed the attached document to some rimfire bench rest friends of mine who thought it was extremely valuable. Don't let the page count put you off...its mostly large format pictures

 

[KnowNothing256]

I'm wondering what influence the C4 soak had. For perspective, my cleaning regimen for both my Vudoo and my RimX over thousands of rounds is to soak the carbon ring with C4 for ~15 minutes, push that wet patch through the bore, use the back of it to wipe carbon off the crown, then a series of dry patches until they come out white.

So, most of the bore only sees one patch of C4 and is immediately wiped dry.

If I understand OP correctly, the lighter of the two colors in the borescope photos is what most of the bore looks like? It's the very dark grey discoloration that is unusual and only located near the chamber?

 

[hafejd30]

I'm wondering what influence the C4 soak had. For perspective, my cleaning regimen for both my Vudoo and my RimX over thousands of rounds is to soak the carbon ring with C4 for ~15 minutes, push that wet patch through the bore, use the back of it to wipe carbon off the crown, then a series of dry patches until they come out white.

So, most of the bore only sees one patch of C4 and is immediately wiped dry.

If I understand OP correctly, the lighter of the two colors in the borescope photos is what most of the bore looks like? It's the very dark grey discoloration that is unusual and only located near the chamber?

The white I believe is the leading

 

[KnowNothing256]

The white I believe is the leading

Let's hear back from OP, hmm?

 

[hafejd30]

Let's hear back from OP, hmm?

He states in the original post his question is concerning the “whitish hard deposit”

I had the same in my B14R. It’s leading.

But we can wait for the OP to confirm your question

 

[bobby1028]

Snyper - I'm not a rimfire guy but I have passed the attached document to some rimfire bench rest friends of mine who thought it was extremely valuable. Don't let the page count put you off...its mostly large format pictures

Interesting read, thanks Baron23. Puts a lot of the myth's to rest...hopefully.