LiveLife
Member
rcmodel can give his reasons but calculating taper crimp is something I learned from rcmodel while lurking for years on THR.vaalpens said:rc, Thanks for the information, but can you explain how you calculated the measurement or is it based on calculation and lots of experience.rcmodel said:Try to adjust your seat & crimp die to give you a finished case mouth measurement of:
9mm = .376".
.40 S&W = .421".
.45 ACP = .471".
That will match most factory taper-crimp I have measured.
The reason why I am asking is that you get a different number when subtracting the bullet diameter from the suggested measurement. I am not questioning the suggested measurement, just trying to understand the calculation
What I realized from amount of taper crimp rcmodel often suggested is that it's twice the thickness of average case wall of .010"-.011". So adding .021" to the diameter of the bullet will give you:
.355" + .021" = .376"
.400" + .021" = .421"
.451" + .021" = .472" (although I typically use more around .471" - maybe 45ACP brass walls are thinner?)