Not a pretty sight: the view from inside your bore

Do not buy a borescope to look at your rifles’ bores unless you are prepared to be confronted by the ugly truth. What you might see may shock and dismay you. 

Could the bore of your favourite rifle be that bad with that amount of combustion residue and wear?  

As a result of peering down the bore, will you have to change your cleaning process or liquids? 

The realistic answer to both questions is probably yes.

Rifle cleaning
Typical blackened patches after cleaning out hard carbon

As one who has used more or less conventional methods of bore cleaning over many years, I was interested to see if a change in chemicals had worked or failed. 

For a long period, I coated all bores between shooting sessions with a 50/50 mixture of Hoppe’s #9 and Penetrene. 

I used conventional bore brushes and a variety of different liquids to keep the bores clean but a few years ago I changed to Bore Tech Eliminator, which does not require a metallic brush. 

The initial two patches down the bore are saturated with Brake Clean to get rid of all the loose material before using patches and a non-metallic brush with Eliminator.

During load development, I have always thought that perhaps a perfectly, chemically clean barrel might not be a requirement, so I fouled the barrel with at least one shot after cleaning. 

Although patches might almost be clean immediately after cleaning, the storage liquid showed some green when patched out before shooting, proof perhaps that it works?

In my opinion, borescopes are useful for monitoring bore condition and to further ascertain if the cleaning regime is working. This may bring about a change in the process depending on the liquids used — there’s no longer any place to hide! 

Rifle bore cleaner
It may be one of Ron’s preferred liquids but normal cleaning liquids like this will not attack hard carbon

The other issue of interest is the hard carbon that accumulates just in front of the cartridge mouth. If not removed over time there is a gradual tightening of the bore when a patch is inserted. One US writer described it as hard carbon or carbon on steroids, and he might be right!

A retired metallurgist suggested to me that none of the current liquids used to clean bores will touch this hard carbon. 

How far it extends down the bore is a matter of some dispute, possibly depending on the cartridge or a specific type. 

I believe this type of carbon is unavoidable. Further, it is interesting that the American barrel maker, Lilja, suggests the use of bore paste every 750 to 1000 rounds.

When I got the borescope, the first rifle I inspected was the family Husqvarna in .270 Winchester, which dates from the early 1960s. I was its third owner and the rifle may have had over 3000 rounds down the barrel.

I considered that the bore’s life had expired, and had no illusions about what the borescope would show. 

Isso bore cleaning paste
Isso paste used to scrub the bore

Yes, there was a ring of carbon just outside the case mouth followed immediately by a ring of heavy fire-cracking that moved forward onto the lands. This continued further down the bore. 

All the lands were ragged on the edges with fire-cracking on top. There was also a fair bit of pitting between the lands. 

No wonder velocity had reduced over time.

The second barrel scanned was my .22-284 Imp (40-degree shoulder), which had 240 rounds logged through the bore. 

Initially, the borescope picture was the same, but with no evidence of copper in the bore at all. By chance, the original gunsmith inspected the bore recently and found it to be in good condition; he approved of my cleaning methods.

I take care so that there are no long strings of shots and the barrel is kept cool. 

I suspected some hard carbon build-up and this was confirmed by two dirty black patches with Isso paste on them. No evidence of copper fouling, so it appears that the normal bore cleaning regime is working.

Perhaps the easiest way not to ruin a bore is to contain the heat by shooting at a controlled rate and cleaning frequently.




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Ron James