|9mm Parabellum with 4.5 grains of Unique powder on the left. 9mm Parabellum with about 3.0 grains of Unique on the right.|
|All the standard disclaimers: "Safe in my gun might not be in yours yada, yada." My plinker load is Crown Bullet's 125 grain cast round nose, 4.5 grains Unique and a COAL of 1.145"|
I was reloading some 9mm Parabellum (aka, 9mm Luger) when I ran into a problem I had never encountered before.
|This is a Lee Precision Powder Measure and is nearly identical to the one I have.|
My procedure is to set up my powder measure, verify the weight of the powder dropped and then start loading. I load one-at-a-time. I drop the powder, visually inspect the powder level, place the bullet on top of the case and then seat it. Single piece processing greatly reduces the possibility of a double measure of powder.
As noted in an earlier post, Unique is a powder that is subject to settling. That means that each shell casing will look a little bit different with regard to how far up the sides the powder charge reaches.
When suddenly I noticed....a short charge. My procedure is to dump the short charge back into the hopper and re-throw the charge because the most likely cause is powder bridging or lack of tapping. The second and third throws were also short. What the heck!
|The black plastic bottom of the hopper can rotate relative to the red plastic storage bin.|
|This rotation feature opens and shuts a valve to make it easy to empty remnants of powder when switching loads. This shows the valve completely open.|
|This photo shows the valve almost closed.|
Process Failure Modes and Effects Analysis has a very cynical view of human inspection.
PFMEA is a structured quality methodology that marries the intuition of humans with the ruthless efficiency of mathematics. "Experts" (plural) create a list of every possible thing that can go wrong with a process. As we have seen with my little reloading problem, this is a dynamic, living list.
|Different industries will have different "scoring" but this one is pretty typical. The main point is that 100% manual is given a "6", or 600% greater of passing a defect than "almost absolute certainty that defect will be caught".|
Each "failure mode" is evaluated for its impact on the customer. Each impact is given a severity rating. In the case of a short charge, consequences could range from the bullet getting stuck in the barrel (very bad when the next round is fired) to not enough zip to cycle the action (that is why we practice "clearing drills").
History, as best as can be remembered, is reviewed and an attempt is made to determine how often each failure mode happens. That frequency is also given a rating. These frequency ratings tend to change a lot as detection methods improve. More than one "once in a blue moon" problem was found to occur several times a day, in short spurts after better detection was implemented.
The three numbers are multiplied together to create an overall risk score. Risk is the interaction of severity, frequency and likelihood of escape.
The first generation of living with and incorporating PFMEA into your process revolves around improving detection.
I opted for a form of double-inspection. I am already looking at the output (the product). I already noted that the inspections are ambiguous due to settling. The rational response is to make the process more visual.
This is what I did.
I, being anal, will do that but I will use a paint pencil because tape can peel off.