Is it possible for the bore and the chamber to be non-concentric ?

[hemiford]

I would think that if the barrel is centered in a lathe when the chamber is cut and reamed,
then the chamber would always have to be concentric with the bore, because that is how
the rifle bore itself is cut. Same with the barrel threads.
The outside surface contour of the barrel also must be concentric for the same reason,
although this is of somewhat less concern.

I'm trying to eliminate things to worry about. If the brass or ammo is out-of-round, that can be
dealt with separately and solved. I'd really like to believe that the barrel is never part of some
out-of-round problem.

 

[lancetkenyon]

Absolutely can happen.

 

[Dmagna]

The

I would think that if the barrel is centered in a lathe when the chamber is cut and reamed,
then the chamber would always have to be concentric with the bore, because that is how
the rifle bore itself is cut. Same with the barrel threads.
The outside surface contour of the barrel also must be concentric for the same reason,
although this is of somewhat less concern.

I'm trying to eliminate things to worry about. If the brass or ammo is out-of-round, that can be
dealt with separately and solved. I'd really like to believe that the barrel is never part of some
out-of-round problem.

The chamber should be cut centered on the bore not the barrel it's self. Barrels can be turned and if there is wobble it would have an effect.

 

[Mikecr]

Past barrel finishers of mine drilled 1st, and then run the finish reamer in with pilots provided in my reamer sets.
My rough reamers have never been used.

 

[243winxb]

Seen an oval chamber in a Rem 760 30-06. A small base die allowed reloads to chamber.

 

[Mallardhammer]

How the barrels sits in the lathe in relation to the OD of the barrel, has nothing to do with how concentric the chamber is to the bore.

 

[stiff neck]

I had a problematic Black Hole Weaponry custom barrel in 6x6.8spc, and sent it back. They confirmed the throat was out of spec and the chamber was cut non-concentric. They made and sent me another one that had the same exact issues, which they confirmed. Unbelievable. After a lot of lying on their end about refunding my money, they eventually sent my refund and a new 223 barrel. I sold that barrel without opening the box and put the money towards a Shilen, which is amazing.

 

[hemiford]

OK. Wow.
This is not something I want to hear.
I must not have a clear understanding of various barrel machining processes.
This seems pretty fundamental, how can it go wrong ?

How do you go about checking if your chamber is not concentric with the bore ?

 

[pdog shooter]

Yes

 

[hemiford]

Does this happen with predominately mass manufactured rifles, not customs ?

 

[stiff neck]

How do you go about checking if your chamber is not concentric with the bore ?

First clue was my bullets were engaging the lands unevenly. BHW said it was probably just a sharp edge on one side of the lands or a burr that would even out once it was broken in. But I was also getting pressure signs with moderate loads. That may have been caused by the short throat forcing me to seat bullets super deep and most loads were compressed. Accuracy was also terrible. BHW diagnosed the non-concentric bores and they eventually figured out that PT&G had incorrectly re-ground their reamer which they used on both of my barrels resulting in the short throat.

 

[MagnumManiac]

Does this happen with predominately mass manufactured rifles, not customs ?

Simple answer is this, regardless of type of pilot used, a reamer, any reamer, wants to follow the rifling and not the bore, which can make it start eccentrically to the bore…it just happens. Any barrel maker will tell you the same, it may not be common knowledge, but it is more common than you might think. My custom barrel on my 22-250AI barrel is off by about .015", and I use all the best indexing tools you can buy…oh well, it happened.

Cheers.

 

[BillLarson]

First clue was my bullets were engaging the lands unevenly. BHW said it was probably just a sharp edge on one side of the lands or a burr that would even out once it was broken in. But I was also getting pressure signs with moderate loads. That may have been caused by the short throat forcing me to seat bullets super deep and most loads were compressed. Accuracy was also terrible. BHW diagnosed the non-concentric bores and they eventually figured out that PT&G had incorrectly re-ground their reamer which they used on both of my barrels resulting in the short throat.

First clue was my bullets were engaging the lands unevenly

Be careful with this statement.If you are finding lands with trigger in place or ejector in place or extractor in place this can happen..... and give you a false idea on whats going on....

 

[cohunt]

I have a muzzle that was threaded non-concentric by a well known, well respected custom rifle builder here from CO (peyton area). You can physically see it just by looking at it.

He swears it can't be -- I wouldn't ever use him again