Doby45 wrote:
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I was not sure if the HP or FP made a difference.
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Well, it CAN. The reason is that a hollowpoint bullet must be a little longer than a flatpoint bullet of the same weight, because the hollow takes some room inside the bullet. So, for the same overall cartridge length, the hollowpoint must sit deeper in the case and leave less room for the powder. That makes the pressure higher.
How much higher depends on how big the hollow is. It does not take much change in seating depth to cause big changes in pressure for small cases like 9 mm and 40 S&W.
So, if you substitute bullets of the same weight but different shape in these cartridges, you should adjust the seating depth so that the substitued bullet leaves as much room inside the case as the bullet for which you have data. Often that adjustment is something less than 0.050", but that is enough difference to really matter.
As an example, I ran a Quickload calc with the Hornady 180 gr HAP bullet and set the charge to produce 35,000 psi (the SAAMI max for this cartidge). Then I substituted the Hornady XTP-HP, which seats 0.020" deeper for the same COL of 1.135". The pressure for the same charge shot up 5335 psi to over 40,000 psi!
More scary, there is another 180 grain .40 pistol bullet in the QuickLoad library called "Hornady FMJ-FPENC." I don't understand what that is, but it is even longer and seats 0.046" deeper in the case for the same COL. The same charge of of powder with THAT bullet calculates out to a pressure of over 50,000 psi!
So, YES, substituting bullets of different shapes in this cartridge can get you into BIG trouble, even though they are the same weight.
SL1