I put togehter my first last monday. I got my complete upper and barrel so it was head spaced and all that good stuff. After fireing it this weekend I noticed that the firing pin had some marks on it. Not from carbon but small notches, around the neck were the carbon ring usually builds up. any Ideas on what this could be from... Im sure they werent there when I got my upper (I gave it a good look over). Other than that it is very fun and has a tight fit. I love it to death. I was planning on taking it to a real range to really zero it in. should I worry about the pin or just keep a close eye on it?

Sounds like the back of the bolt has a ridge that is indenting on the firing pin collar.

A little sandpaper (400) your thumb and the bolt end spun sanded will solve the problem.

If the marks are on the outer edge of the collar, the either the hammer is slightly binding up as the carrier/firing pin moves forward over it, or the back of the carrier is rough as hell and leaving some impact marks (No really fix since the carrier is heat treated and getting out the mill marks removes the Treating).


As Tweak posted, a Photo will narrow the problem way down to give you the correct single solution.

I would like to apologize for the quality of the picture.  My camera is not very good (at all).  Under a magnifying glass the marks look like small concave marks ( U shape) getting deeper closer to the arch.  the marks have the open end of the "U" facing towards the part that hits the primer


http://storage.msn.com/s1pZ8pl_R1n1zGM07_jx_pvOwE454KBXW8HAsjJbaM8ZyziuPnR6jKV-UbN0f0mTipYCcS04Ap4yf4aBxv-6vUpaA/00.jpg?MdToken=201445692793684

If the indents are circler around the inside, then roll sand the bolt to remove the high ridge at the firing pin entry point.

If the marks/damage is between the circler indent, but not at the very edge, it's the back of the carrier that doing the damage.

If the marks are at the very edge, then it's the hammer.

Now the good news, unless the firing pin is taken a beating in a very short time (say a few hundred rounds), don't worry about it.  Normally, I chew them up in my rifles (chipped tip, or ringed at the bolt face side) around the 30,000 mark.  If you can afford the ammo to shoot that much, then replacing a $10 firing pin every 30,000 rounds should be the last of your worries.

Quoted: Under a magnifying glass the marks look like small concave marks

Magnifying glass ???  It is my guess that what you are seeing are the machining marks.  The FP collar is probably cut on a lathe.  It is typical for a lathe tp leave these tiny grooves.

If you have to use a magnifying glass to see these marks, then I feel strongly that it is lathe machinig marks, which is normal.

It shouldnt be that big of a deal, if you can just throw a new pin in like that.   They are really small, thats why I wasnt sure what it could be from.  I think I will keep an eye on it and if it gets worst then it inst machining marks.  A guy that helps me with my rifle told me it was either from machining or from the internals of the gun.  After looking it over and reading I think it is either from the hammer or machining marks because the only part that would be close to that part of the pin would be the hammer.  either way its not such a big deal as I thought it was.


Thanks for the advice