Eric
1 February 2014, 01:31
About 10 years ago I arrived at my agency's range for rifle training, which began with shooting a rifle qual course. This included shooting up the currently issued duty ammo I was carrying. During the first course of fire, I encountered a deafening click instead of a bang. A primary malfunction clearance resolved the issue and I pressed on. I later recovered the round that had failed to fire and found that it had a solid primer hit and would not fire after additional attempts. I didn't feel especially warm and fuzzy knowing that the first round in my duty mag wasn't going to fire if I had needed it.
Was the round defective from the factory or had I done something to induce the failure? Obviously there's no way to know, but this experience is something I make reference to when reminding our folks to not reuse ejected rounds for duty. The idea is that the free-floating firing pin lightly contacts the primer each time the round is chambered (we've all seen the small dimple mark left) and after this occurring several times, the primer material is chipped way compromising reliable ignition.
So, how many times can a round be re-chambered before it fails to fire? Picture an officer on a busy shift in a high crime area, who breaks his patrol rifle out on a regular basis. It would not be unreasonable to have chambered a round twenty times before he is issued fresh ammo. If the officer were to reuse that same chambered round each time, would it still fire? I certainly don't know.
A few days ago this unresolved question popped into my head while at the range, so I re-chambered two different rounds twenty-five times each, shown in the photo below. Both had impact marks deeper than those from a single chambering, yet not as deep as a being struck when the trigger is pulled. It turns out, both rounds fired just fine. I tried again and chambered each round fifty times, with the same results. By then, I had lost daylight and the public range I was on was closing, but I'm curious to try the test with a higher number of cycles.
Has anyone studied this in detail, perhaps testing to the failure point? A lot of variables could come into play, as far as the type of round (mil-spec primer vs. commercial) and specs on the rifle.
http://img.photobucket.com/albums/v503/AR15forme/IMG_3397.jpg (http://smg.photobucket.com/user/AR15forme/media/IMG_3397.jpg.html)
Was the round defective from the factory or had I done something to induce the failure? Obviously there's no way to know, but this experience is something I make reference to when reminding our folks to not reuse ejected rounds for duty. The idea is that the free-floating firing pin lightly contacts the primer each time the round is chambered (we've all seen the small dimple mark left) and after this occurring several times, the primer material is chipped way compromising reliable ignition.
So, how many times can a round be re-chambered before it fails to fire? Picture an officer on a busy shift in a high crime area, who breaks his patrol rifle out on a regular basis. It would not be unreasonable to have chambered a round twenty times before he is issued fresh ammo. If the officer were to reuse that same chambered round each time, would it still fire? I certainly don't know.
A few days ago this unresolved question popped into my head while at the range, so I re-chambered two different rounds twenty-five times each, shown in the photo below. Both had impact marks deeper than those from a single chambering, yet not as deep as a being struck when the trigger is pulled. It turns out, both rounds fired just fine. I tried again and chambered each round fifty times, with the same results. By then, I had lost daylight and the public range I was on was closing, but I'm curious to try the test with a higher number of cycles.
Has anyone studied this in detail, perhaps testing to the failure point? A lot of variables could come into play, as far as the type of round (mil-spec primer vs. commercial) and specs on the rifle.
http://img.photobucket.com/albums/v503/AR15forme/IMG_3397.jpg (http://smg.photobucket.com/user/AR15forme/media/IMG_3397.jpg.html)