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Posted: 2/4/2013 9:52:36 AM EDT
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I am relatively new to reloading. I took some .223 reloads out to the range this weekend. All went well, however, upon inspecting the brass, I noticed that on 3 of them (out of 80 total I shot) the primer dimple where the firing pin struck was black. Upon inspecting the dimple, I noticed there was a very small hole in the primer. Any ideas as to what could cause this? The primers were Winchester Small Rifle (WSR) primers. The primers were seated just below flush. The brass was Federal American Eagle once fired from the same rifle (Smith & Wesson M&P 15). The 3 primers that had an issue were loaded with either 25.9, 26.0, or 26.8 grains of Winchester 748 powder, pushing a 55 grain Hornady SP bullet. This is a relatively light load for W748. The pictures are of 2 that were punctured (bottom) and 2 that were not (top)
http://i46.tinypic.com/2rfetjb.jpg http://i45.tinypic.com/2dcdb3r.jpg |
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The 3 primers that had an issue were loaded with either 25.9, 26.0, or 26.8 grains of Winchester 748 powder, pushing a 55 grain Hornady SP bullet. This is a relatively light load for W748
Not really "light". Hodgdon lists 26.3gr as Max for the 55gr bullet. However, If your scale is correct I don't think your loads are hot enough to pierce a primer. I have pierced a few WSP in my 221 Fireball with med-heavy loads. Switched to 7 1/2 and no more problems. |
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That's usually caused by high pressure.
I wonder if this is the first time you've looked at the primers from cases fired in that rifle; you may have been getting pierced primers with factory ammunition all along without noticing. In any case, your next step is to inspect the nose of the firing pin to find out how badly it's cratered. If only a couple of cases have pierced the damage might be small enough (barely noticeable) to repair by polishing the nose of the pin. A large crater means the firing pin is ruined. |
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Pierced or Blanked Primers.
1. Check the firing pin, it should have no gas cutting or deformities. 2. Firing pin protrusion should be checked. Internet search shows .055" to be about right for an AR15. Check with a gun smith as each firearm IS different. 3.The firing pin must stay in contact with the primer on firing. A weak hammer spring on an AR or a weak firing pin spring like on a Rem 700 bolt action will let the firing pin rebound on primer piercing when the hot gas pushes the pin backwards. 4.If the hole the pin sits in is to larger in diameter, the primer flowes back into this hole till the center of the primer separates and fall into the action or travels into the firing pin area. Bushing the firing pin hole will fix this. Or you may want to try a magnum primer with a thicker cup. Military ammo may have a crimp that needs to be removed before seating a new primer. The crimp is removed by reaming or swaging the primer pocket. Swaging may be needed here so the prime can be seated lower in the pocket. High primer = misfires & pierced primers. There is also a high pressure sign visible. The reloader was using a "starting" load and CCI 400 primers. The CCI 400 is thin & soft, change to a mag. or Rem. 7 1/2 primers. The pressure sign may have formed on firing the factory ammo. I just shot some XM193F factory, the web area expanded .0015" on firing. This is a sigh of a "hot" load. 
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| The firing pin looks like it has very minimal damage, if any. I have some Rem 7 1/2 primers I will try to see if that fixes it. I have noticed the Federal cases vary widely in length. The lengthiest are 1.752" and the shortest are ~1.733" Could the shorter cases be causing hire pressures, resulting in the punctured primer? |
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Your reloads look to be very high pressure. As a result, you pierced the primers.
Back off on the powder charge. 3/80 is WAY too high a failure rate. Your firing pin is probably toast, too. Three exposures to super-hot gases (plasma?) coming out of the hole = bad news for pin. A magnifying glass or higher should be used to inspect the pin for damage. |
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Quoted:
OP, do my eyes deceive me, or am I seeing primer crimp rings on your FACE commercial brass? Is nothing sacred with ATK anymore?   I've been picking up commercial FC brass with crimps for a couple years now. This is not something new. This past summer I started to find and have people give me Remington commercial brass with crimps. |
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Quoted:
The firing pin looks like it has very minimal damage, if any. I have some Rem 7 1/2 primers I will try to see if that fixes it. I have noticed the Federal cases vary widely in length. The lengthiest are 1.752" and the shortest are ~1.733" Could the shorter cases be causing hire pressures, resulting in the punctured primer? I have one rifle that will Perice 3 out of 50 Rem 6 1/2's loaded light. My other rifle was mistakenly used with full power loads for 2 years with the 6 1/2's and never pierced one. My point is that different tip profiles and FCG components (springs) can cause piercing too. One common mod for the firing pin of the French MAS 49-56 which is very prone to slam firing is to stone the firing pin tip to a blunter profile. I think it would be very possible to do the same to an offending AR firing pin. A simple stoning of the tip to basically make it less sharp could be all you need to fix your problem. |
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