Is it a carbon ring?

[HighUintas]

Unfortunately the hornady coal gauge isn’t accurate, unless you have made your own modified case from a piece of brass fired in your rifles chamber.


Sent from my iPhone using Tapatalk

Why does it have to be a piece of brass fired in my chamber?

 

[Brendan]

Why does it have to be a piece of brass fired in my chamber?

It doesn't, the measurements don't need to be accurate, just need to be consistent. Just remember that with any of these gauges, you're not measuring the actual CBTO, it's all relative. Then, test your seating depth / jump using the same cbto comparator, and when you find a depth your rifle likes - do that. Just keep your measuring tool and methods the same (e.g. my sinclair and hornady comparators have different inner diameters, so will give different CBTO lengths)

I was doing it using Alex Wheeler's method before I realized it doesn't matter...

 

[deadwolf]

Why does it have to be a piece of brass fired in my chamber?

Because the hornady brass coal piece is just at saami spec. Your brass fired from your rifle is sized to fit your chamber exactly.


Sent from my iPhone using Tapatalk

 

[HighUintas]

Yea, after thinking about it I see how it doesn't give a true measurement. I'll have to use it for monitoring my throat erosion. Maybe I'll thread a case so I can use that for a true measurement.