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Posted: 3/9/2006 11:20:50 AM EDT
I'm a little worried on this~~~

When I chamber a round and then eject it un-fired the primer has a strike mark on it. Not just a fluke, I chambered and ejected several rounds and they all have a dimple on the primers.

Normal?

Seems odd.

Thanks
Link Posted: 3/9/2006 11:22:10 AM EDT
[Last Edit: 3/9/2006 11:22:32 AM EDT by M4A1OwnsYou]
I forgot the reasoning, but don't worry about it. It's not enough to cause any harm.
Link Posted: 3/9/2006 11:22:58 AM EDT
Normal. The firing pin floats, and will move forward and touch the primer when chambering a round.
Link Posted: 3/9/2006 11:25:32 AM EDT
[Last Edit: 3/9/2006 11:27:12 AM EDT by DaveS]
M4A1OwnsYou just wants you carted off by the goons when your rifle runs away.

I'll buy it from you for $325.00 w/shipping included.

If I can get it to run properly, fine. If not... hell, I'll have one more expensive lower receiver... if it is an ABC rifle that we are talking about.

Dave S

­



Link Posted: 3/9/2006 11:26:34 AM EDT
[Last Edit: 3/9/2006 11:26:48 AM EDT by M4A1OwnsYou]

Originally Posted By DaveS:
M4A1OwnsYou just wants you carted off by the goons when your rifle runs away.

I'll buy it from you for $325.00 w/shipping included.

If I can get it to run properly, fine. If not... hell, I have one more expensive lower receiver.

Dave S

­





Link Posted: 3/9/2006 11:32:40 AM EDT
[Last Edit: 3/9/2006 11:34:03 AM EDT by Machine249]
I read something about this not too long ago. The explaination was something along the lines of the fact that the firing pin is loose inside the bolt (no spring to keep it back until the hammer pushes it forward), so when the bolt slams forward inertia keeps the firing pin moving forward and into the primer.

In short, as long as the mark is not too deep (somewhere along the lines of barely visable) I wouldn't worry. I've never heard of an AR15 slam firing, so I wouldn't be too concerned. Keep in mind the first part is information I read elsewhere, the second part is my opinion.
Link Posted: 3/9/2006 11:40:14 AM EDT
Try different MAGS and SLINGS to see if this Dangerous condition will go away!
Link Posted: 3/9/2006 11:43:09 AM EDT
Normal
Link Posted: 3/9/2006 11:50:01 AM EDT
Just another reason to always make sure the weapon is always pointed in a safe direction.
Link Posted: 3/9/2006 11:53:11 AM EDT
[Last Edit: 3/9/2006 11:53:20 AM EDT by FALARAK]

Originally Posted By markm:
Try different MAGS and SLINGS to see if this Dangerous condition will go away!



Link Posted: 3/9/2006 12:09:17 PM EDT

Originally Posted By thatsthesignal:
I'm a little worried on this~~~

When I chamber a round and then eject it un-fired the primer has a strike mark on it. Not just a fluke, I chambered and ejected several rounds and they all have a dimple on the primers.

Normal?

Seems odd.

Thanks



As you can see (once you get past the non-responsives) it's perfectly normal. Quick tip: since you're relatively new here. Make "search" your friend, it will serve you well, ie: Recent thread that came up when doing a search for Suject = "dimpled primer" in the AR15-15 Board, Last 30 Days.

This is not to discourage you from asking questions, God knows I have, lol. Often you'll benefit from many perspectives on a given topic (though this one is pretty straight forward).

You'll get to know who knows what they're talking about soon enough.

Welcome to the site.
Link Posted: 3/9/2006 12:26:13 PM EDT
[Last Edit: 3/9/2006 12:27:38 PM EDT by I-M-A-WMD]
Although it is normal to have a firing pin dimple to the primer, it is definately something that should always be checked out to determine if the dimple is excessive. I have had a slam fire w/ one of my BFI ARs. What you need to ensure is that the dimple is not excessively deep due to either a sharp firing pin and/or a long firing pin.

When I had my ND due to a FP strike to the primer there were certain contributing factors.

1) The firing was "sharp". In other words, it was very rounded almost to a point.
2) The firing pin may have been "long". Not enough to puncture the primer when normally shooting, but left a deep indentation on fired casings.
3) I had the magazine out and single loaded the round into the chamber with the bolt locked back via the bolt catch.

Due to not having a magazine, with the round in the chamber, the bolt was free to slam forward as fast as it could. I was at a bench and when I pushed the bolt release the round detonated and struck downrange. My dad was shooting next to me and when he saw the dirt fly between the targets and our bench, he figured I'd had an ND due to poor trigger control. I hadn't moved a muscle after the round fired and told him, "Look at where my finger is!" I'm a lefty so I used my trigger finger to disengage the bolt catch. My trigger finger was still placed on the bolt catch...

We puzzled over how it could happen and performed some testing to check the depth of the dimple left on the primer by the firing pin. The results were:

A) Chamber charged from full magazine= Slight dimple.
B) Chamber charged from magazine w/ only one round left= Slightly deeper dimple than "A".
C) Chamber loaded manually w/ bolt released to charge= Dangerously deep dimple to primer.

Couple the above w/ a slightly high and/or soft primer= Unintentional detonation.

I'd suggest running these tests to see if the dimples are excessive or acceptable to you. With a bit of honing on the firing pin tip, my Bushy is good to go. Just another example of why muzzle awareness is so very important.

Sly
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