Quote:
|
We used scrounged brass (I know what some will say to that), that was tumbled clean and sized with a Lee 40SW carbide sizing die; CCI small pistol primers; Rainier 180gr HP's; and 5.3gr of W231.
|
Two problems:
#1 - Scrounged brass.
#2 - 180gr HP bullets.
Scrounged brass, particularly in the .40, is a bad idea. You need to know the history of your brass so that you can monitor its bulge, number of times loaded, growth/shrinkage and such.
However, in the .40 S&W, 180gr bullets are a BAD IDEA. Dillon Precision was handing out fliers in their store a couple years ago urging reloaders not to use 180's in their .40 reloading. I was loading for .400 corbon at the time and bought some 180gr cast bullets and got the flier and explanation from one of the folks there.
180's fill up too much of the internal case of the .40. When you have a hollowpoint 180, it fills up even more of the case than a solid 180. That cavity represents lost material that has weight. A hollowpoint 180 is longer than a solid 180, so it protrudes even further into the case interior.
My guess as to what happened:
Failure #1 - You used mixed headstamp brass. Different brass makers use different thicknesses. This can affect the strength of your crimp later on.
Failure #2 - You didn't monitor the OAL of the naked brass casings. Some cases may have been fired more often than others. Handgun brass tends to shrink between firings, just slightly. This affects the strength of your crimp later on.
Failure #3 - You used 180 grain bullets, the least tolerant of internal combustion volume in a high pressure cartridge.
Failure #4 - You did not crimp sufficiently to avoid bullet set-back during the feed process.
Failure #5 - You did not hand cycle a control set of reloaded rounds through your gun, looking for before and after OAL to see if set-back was going to be a problem.
Result - Your gun blew a case head and was damaged.