Ring inside Benelli barrel

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Went thru and was cleaning my 2 benelli semi autos today and as i was admiring the finish on the beautiful chrome lining these fine shotguns have, i noticed a distinct black ring that looks to hold fouling and does not want to give it up. The rest of the barrel and chamber look and feel like the inside of a glass tube.

One is a M1 and the other is a M4 they both have the same ring in the same spot which is 3" in from the breech (just after the shell). Which leads me to think its just baked on there from firing. Is this fouling and debris etched on to the bore or has the chrome erroded?

The older M1 barrel ring has fouling embeded on the said ring that keeps on coming off as you run a wet patch thru it, the M4 barrel is newer and has no fouling residue coming from it and is still there. Theres no build up that can be felt if you run a pick gently over the area. It just tranistions from smooth to slighty gritty back to smooth.

Called benelli and they have never heard of such a thing and had no real answer for me and said it could of been factory grease that was left in there. He told me to call back tomorrow and talk to tech support before 3pm.

IMG-20130515-00992.jpg
 
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That may be the forcing cone, that you are looking at. It looks like a ring because the light isn't reflecting off of it.


You are correct. So it was reamed after it was chromed? i dont understand why it wouldnt be left chromed as well. The barrel cleans very easily nothing sticks to it because of the chrome in there. Only problem spot is this forcing cone area. Maybe it gets blasted from the shot and lost the polished finish i guess.
 
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MisterHappy

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there should be no contact between the barrel, at any point, and the shot load, when using modern plastic wads.

The forcing cone is an area of transition, where the internal diameter of the barrel goes from being large enough to accept the shell (the chamber), and where the internal diameter is tight enough to "seal" around the wad.

It's likely what you're seeing is just "shadow" due to the forcing cone being at an angle to the parallel line of the bore, but a call or email to Benelli should get you the answer. I can't imagine reaming it after chroming.

If my description is vague, look at a shouldered rifle case - the shoulder is the forcing cone, the neck the bore, and the main body of the case the chamber.
 
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The only gripe i have is that the forcing cones surface is very textured even when clean it feels like its been blasted with abrasive blast media verses the rest of the barrel and chamber which are polished and are slick.
 
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The only gripe i have is that the forcing cones surface is very textured even when clean it feels like its been blasted with abrasive blast media verses the rest of the barrel and chamber which are polished and are slick.

I am not a gunsmith or a Benelli engineer, but that might be intentional. I do know that you want the wad slowed down relative to the shot column before it breaks the muzzle to reduce or eliminate having the wad disrupt the shot pattern. The forcing cone sounds like an early place to separate them, but maybe by then it's done all that was needed in terms of protecting the shot from the initial force of acceleration.
 
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