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Posted: 2/28/2010 3:49:09 AM EDT
| I picked up a new RRA upper for a lower I had and was cleaning it. I noticed the tip of the firing pin looked white when it poked through the face of the bolt. Upon looking at it with a magnifying glass the tip is pitted to hell, it looks like the moons ' surface. The upper is brand new. This doesn't appear normal. Is it safe to shoot, I wanted to go to the range today. |
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Almost kind of normal to see the very center of a firing pin cratered (about the size of a pin tip). The way pins are produced (read lathe'd) unless the cutter is set just perfect center line on the stock and adjusted as the cutting tool wears, when the cutter gets to the very tip of the FP while producing it, the cut off section will snap off from the FP, and leave such a surface.
Now having said that, go fire the rig and put the problem in the back of your mind. If you do find that the FP is piercing primers, then you have the choice of either correcting the FP, or have your defer'd out for a new one. Out the gate, FP protrusion out the face of the bolt when fully seated should be .032 to .037 for 223/5.56. So with that in mind, lets say that you have a FP that is badly pitted. For starters, chuck the back end of the FP in a drill or lathe and spin sand the tip until you have removed the pitting and re contoured the tip of the pin. Now grab the bolt and a caliper, and with the FP maxed out in the bolt take a read of the protrusion of the tip. Lets say that the protrusion is coming up .005 short. If you using a lathe, then set back the stop collar of the FP 5 thousands (where the FP collar contacts the back of the bolt, and you are done. If you are using a drill, then you will need to use a file and measure a few times alone the way to get it right. Now the big one, if you shear or crack the end off a FP, just replace it. Granted that you could save the FP with a lathe by re contoure'g the entire pin back the needed amount from the tip, but you would need to correctly heat treat the FP afterwards as well (read going to cost you more of your time in just setting up the FP true in the lathe, much less the cost of gas to run the heat treating furnice for a one part at a time, than it would to just buy a new FP). |
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