Emmett Dibble
Gold $$ Contributor
Big lurker, did some poking around couldn't find the answer...
I shoot silhouette. Shoot a lot of lever action silhouette. Pistol cartridge, as the name implies is straight wall cartridges in rifles. 357 is very common.
The problem I am having is carbon fouling, not carbon ring, starting about 3-5" after the leade and ending about 8-10".
The way it presents itself is somewhere around 30 - 40 rounds, about the middle of the match, the carbon build up in the barrel will harden up between relays. You shoot 5 shots in 2 minutes, there is a 30 second break, you shoot 5 more shots in 2 minutes, another 30 second break, then another 5 shots in 2 minutes, then the rifle may sit in the rack for 10-20 minutes and you repeat. About half way through the match the carbon will harden and make the first shot slow/low then the resulting warm/hot shots will come back up to established POA/POI.
I had one rifle that did this before. I have other rifles that don't.It took a while on the current rifle to deduce exactly what was happening. (second one, sold the first one that displayed this phenomenon thinking it was the rifle)
I clean and use a bore scope to inspect. I started a routine of inspecting before I clean and that is how I realized that the problem isn't a rifle/barrel problem but a carbon build up problem.
The particular rifle is a Uberti 1866 in 38 special, 24" barrel and the load is 6.6g Longshot under a Speer 125gr Gold Dot with a very light taper crimp. I have bullet, powder, crimp tested the hell out of this gun and that set up gets me +/- 2 MOA all day long till the carbon build up then the first shot (after the barrel cools off 10 - 15 minutes) prints low (like 6-10"@100 yards) and the report is off... subsequent shots will follow up to where they are supposed to be.
Any ideas? FWIW, the other rifle that did this and I assumed it was just CBF was 357, different powder and bullet.
Picture for clarification...

I shoot silhouette. Shoot a lot of lever action silhouette. Pistol cartridge, as the name implies is straight wall cartridges in rifles. 357 is very common.
The problem I am having is carbon fouling, not carbon ring, starting about 3-5" after the leade and ending about 8-10".
The way it presents itself is somewhere around 30 - 40 rounds, about the middle of the match, the carbon build up in the barrel will harden up between relays. You shoot 5 shots in 2 minutes, there is a 30 second break, you shoot 5 more shots in 2 minutes, another 30 second break, then another 5 shots in 2 minutes, then the rifle may sit in the rack for 10-20 minutes and you repeat. About half way through the match the carbon will harden and make the first shot slow/low then the resulting warm/hot shots will come back up to established POA/POI.
I had one rifle that did this before. I have other rifles that don't.It took a while on the current rifle to deduce exactly what was happening. (second one, sold the first one that displayed this phenomenon thinking it was the rifle)
I clean and use a bore scope to inspect. I started a routine of inspecting before I clean and that is how I realized that the problem isn't a rifle/barrel problem but a carbon build up problem.
The particular rifle is a Uberti 1866 in 38 special, 24" barrel and the load is 6.6g Longshot under a Speer 125gr Gold Dot with a very light taper crimp. I have bullet, powder, crimp tested the hell out of this gun and that set up gets me +/- 2 MOA all day long till the carbon build up then the first shot (after the barrel cools off 10 - 15 minutes) prints low (like 6-10"@100 yards) and the report is off... subsequent shots will follow up to where they are supposed to be.
Any ideas? FWIW, the other rifle that did this and I assumed it was just CBF was 357, different powder and bullet.
Picture for clarification...

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