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Posted: 6/28/2013 5:21:36 AM EDT
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While cleaning one of my rifles tonight I noticed what appears to be etching or pitting on the bolt face. The rifle is 16" carbine length gas system. Round count on the bolt is approximately 7K will a vast majority being Federal XM193, some Winchester 55gn white box and fewer then 150 hand loads.
Any ideas? 
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This is often caused by a primer piercing problem. Once you get a few pierced primers, your Firing pin can get etched and cause more piercing which snowballs into bolt face damage as you see here.
Check your firing pin for damage and get a protrusion guage to see if it's out of spec. If it's damaged, trash it. |
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Normal plasma cutting from blow by past the primer at ignition for the most part, the cutting at the ejector is a bit severe, and the crater on on the other side was caused by a primer pierce that blew a piece of the cup, and caused the indentation/ smearing of such.
I wouldn't call the bolt toasted just yet, but would pull the ejector to clean it up a bit, and maybe chuck the bolt up by the tail in a drill or lathe to do a touch of spin sanding to the bolt face to take any high ridges down so the ammo can seat correctly flush with the bolt face, instead of the high ridges holding the round off the bolt face to cause more problems instead.. |
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Quoted:
This is often caused by a primer piercing problem. Once you get a few pierced primers, your Firing pin can get etched and cause more piercing which snowballs into bolt face damage as you see here. Check your firing pin for damage and get a protrusion guage to see if it's out of spec. If it's damaged, trash it. I checked my ammo from the last range trip and found this . . . 
I'll check the firing pin. The gun functioned without issue after firing this round. Thanks for all the responses, Mike |
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Quoted:
Quoted:
This is often caused by a primer piercing problem. Once you get a few pierced primers, your Firing pin can get etched and cause more piercing which snowballs into bolt face damage as you see here. Check your firing pin for damage and get a protrusion guage to see if it's out of spec. If it's damaged, trash it. I checked my ammo from the last range trip and found this . . . http://i9.photobucket.com/albums/a89/MAP1911/92bda006-088f-4a40-b8b0-8aae5b10d8dc_zps830e2c25.jpg I'll check the firing pin. The gun functioned without issue after firing this round. Thanks for all the responses, Mike The primer is reading signs of over pressure. Are you sure that this is a 5.56 nato reamed chamber barrel, and not 223 rem instead. I'll go out on a limb and tell you to double check the FP protrusion to make sure that is no greater than .032", but again, with the primer showing that much working pressures to almost flatten the primer to pocket crimping edge, it just showing that the factory ammo is hitting too high of working pressure through the barrel. |
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Quoted:
Quoted:
Quoted:
This is often caused by a primer piercing problem. Once you get a few pierced primers, your Firing pin can get etched and cause more piercing which snowballs into bolt face damage as you see here. Check your firing pin for damage and get a protrusion guage to see if it's out of spec. If it's damaged, trash it. I checked my ammo from the last range trip and found this . . . http://i9.photobucket.com/albums/a89/MAP1911/92bda006-088f-4a40-b8b0-8aae5b10d8dc_zps830e2c25.jpg I'll check the firing pin. The gun functioned without issue after firing this round. Thanks for all the responses, Mike The primer is reading signs of over pressure. Are you sure that this is a 5.56 nato reamed chamber barrel, and not 223 rem instead. I'll go out on a limb and tell you to double check the FP protrusion to make sure that is no greater than .032", but again, with the primer showing that much working pressures to almost flatten the primer to pocket crimping edge, it just showing that the factory ammo is hitting too high of working pressure through the barrel. It is a Colt barrel. Definitely 5.56 chamber. It may not be clear in the picture, but the primer is no where near flattened to the edge of the primer pocket. Mike |
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