I've been reloading M1 Carbine since I was a teenager. In the decades since, I've handled a lot of brass. In the last year I have received, from two sellers one in Texas, one in Georgia, brass that has a distinct bulge starting 0.230 inches above the case head. The particulars:
Pistol brass fired from unsupported chambers usually has a distinctive "smile" when resized. When this brass is resized it looks normal and does not have the "smile".
I have included a picture. My first attempts to capture the bulge showed nothing so I used a weak acid to take the shine off the brass for better contrast in the photograph, but the bulge itself remains largely indistinct.
Anything you can tell me will be appreciated.
- The bluge is not present on every case in either lot.
- The bulge is not confined to any particular headstamp.
- The bulge ranges about 0.020 to 0.023 inches displacement from the line of the case wall.
- The bulge covers about 120 to 180 degrees of the circumfrence of the case.
- The bulge is apparent on visual inspection and can also be felt with the fingertip.
- The bulge is continuous along the case wall and a fingernail will not "hang" up on it.
- Visual inspection of the interior of the case with an otoscope reveals nothing different from brass that does not have the bulge.
- Resizing a bulged case seems to remove the bulge since the resizing die reaches below the bottom of the bulge.
- On an M1 Carbine, the recess in the bolt only covers up the first 0.135 inch of the case, so the bulge is not at the point where the bolt meets the barrel. I am not familiar with other guns that are chambered for the cartridge.
Pistol brass fired from unsupported chambers usually has a distinctive "smile" when resized. When this brass is resized it looks normal and does not have the "smile".
I have included a picture. My first attempts to capture the bulge showed nothing so I used a weak acid to take the shine off the brass for better contrast in the photograph, but the bulge itself remains largely indistinct.
- Has anyone seen this on M1 Carbine before?
- Does anyone know the cause?
Anything you can tell me will be appreciated.