Here's one for Sherlock Holmes.
During a session yesterday, the portion of the slide stop that engages the mag follower broke off. As a result the slide wouldn't lock back on the last round.
However, it showed up before the last round. When it happened, there were two rounds still in the mag. What happened was that the round in the chamber didn't fire. I pulled the trigger, the hammer dropped normally, but nothing happened.
I ejected the mag, then opened the slide. What came out was the unfired round. The interesting thing about it was that the primer surface was unmarked. No dimple, no breechface marks, nothing unusual. IOW, no indication that the firing pin struck the primer. There were no other distinguishing marks or blemishes on the cartridge.
As I puzzled over this, I decided to lock the slide back manually. As I did so, something "felt funny." I know this doesn't help much, but I can't describe it in any other way. On a hunch, I emptied the mag, closed the slide, inserted the empty mag, and pulled the slide back to see if it would lock in place. It didn't. A quick inspection of the slide stop showed the breakage.
The gun is a Colt M70 MK IV bought new. It is unmodified except for a set of Bo-Mar sights and rubber Pachmeyer grips. The mags are GI issue and the one that came with the gun. There were no problems leading up to the failure, and the gun has not been worked on in any way between this session and the last one, about a month ago. I had already fired 126 rounds before the failure occurred. The only difference between the ammo I used this time and last time is a greater charge: 6.5 g of Unique versus 6.0 g last time. A look at the table in the Lyman reloading manual shows max safe charge for this bullet (SWC 200g hard cast) is 6.8 g. All charges are weighed before they are poured into the case. Yes, I know this is time consuming, but I prefer to do it that way. All rounds are drop tested before they are put in the ammo box.
When I got home, I disassembled the gun for cleaning. I found nothing unusual, and nothing else broken. No unusual marks or scars anywhere.
After cleaning and reassembly, I loaded my dummy squib round (Traditions, 45 ACP) with a piece of masking tape over the primer area, closed the slide and pulled the trigger. The tape was pierced where the firing pin struck it.
Nothing else seems to be wrong with the gun, and I have a new stop in place. What I don't understand is how a broken slide stop could cause the firing failure.
Any ideas?
During a session yesterday, the portion of the slide stop that engages the mag follower broke off. As a result the slide wouldn't lock back on the last round.
However, it showed up before the last round. When it happened, there were two rounds still in the mag. What happened was that the round in the chamber didn't fire. I pulled the trigger, the hammer dropped normally, but nothing happened.
I ejected the mag, then opened the slide. What came out was the unfired round. The interesting thing about it was that the primer surface was unmarked. No dimple, no breechface marks, nothing unusual. IOW, no indication that the firing pin struck the primer. There were no other distinguishing marks or blemishes on the cartridge.
As I puzzled over this, I decided to lock the slide back manually. As I did so, something "felt funny." I know this doesn't help much, but I can't describe it in any other way. On a hunch, I emptied the mag, closed the slide, inserted the empty mag, and pulled the slide back to see if it would lock in place. It didn't. A quick inspection of the slide stop showed the breakage.
The gun is a Colt M70 MK IV bought new. It is unmodified except for a set of Bo-Mar sights and rubber Pachmeyer grips. The mags are GI issue and the one that came with the gun. There were no problems leading up to the failure, and the gun has not been worked on in any way between this session and the last one, about a month ago. I had already fired 126 rounds before the failure occurred. The only difference between the ammo I used this time and last time is a greater charge: 6.5 g of Unique versus 6.0 g last time. A look at the table in the Lyman reloading manual shows max safe charge for this bullet (SWC 200g hard cast) is 6.8 g. All charges are weighed before they are poured into the case. Yes, I know this is time consuming, but I prefer to do it that way. All rounds are drop tested before they are put in the ammo box.
When I got home, I disassembled the gun for cleaning. I found nothing unusual, and nothing else broken. No unusual marks or scars anywhere.
After cleaning and reassembly, I loaded my dummy squib round (Traditions, 45 ACP) with a piece of masking tape over the primer area, closed the slide and pulled the trigger. The tape was pierced where the firing pin struck it.
Nothing else seems to be wrong with the gun, and I have a new stop in place. What I don't understand is how a broken slide stop could cause the firing failure.
Any ideas?