I shot a near stock .45 in major L-10 for years. I happened to look at the breechface one day and it has a complete circle of pinholes around it. It still shoots great but looks bad.
I always shot WLP or Federal primers. I posted about it a long time ago. I don't know why it eroded. But it's got over 50,000 Rds on it.
I wonder how much it'd cost to fix it?