I Sure Could Use Some Help

[sublimaze41]

Much appreciated. Can anybody speak to the consequences of excessive crimp on .380? How does it manifest? spike in pressure, Kb?


FWIW, I chose the OAL because it cycled well and was mid range for the books I resourced. I got the charge from the Hogdon web site for a 90 grain bullet. 3.4 grains of 231 is smack dab in the middle. My actual velocity was well below the stated velocity (anticipated).

 

[Mal H]

How does it [excessive crimp] manifest? spike in pressure, Kb?

Hard to say precisely, there are too many variables. In general, yes, you will see a higher pressure since the case will hold the bullet a little longer before releasing causing the peak pressure to be higher. How much higher? Again, hard to tell without instrumentation.

Will they KB? Very doubtful. Don't forget we're dealing with a fairly thin brass case which has a very forgiving property in that it is quite malleable as metals go. IOW, the bullet isn't being held in a steel vise, the expanding gases will eventually have enough pressure to cause the bullet to move forward expanding the case mouth at the same time no matter how tight the crimp might be. In fact the pressure will expand the case itself to the inside diameter of the chamber - the bullet has to be freed at that time.

KB's in handguns are usually caused by one of two things, an unsupported area of the case in the chamber in conjunction with one of several other factors, and an overload of powder. Of course there are many more (e.g., headspace problem, weak area in case, excessive OAL, etc.), but those are the main two. You don't have either of those.