You're right, the hollow base matters. I did take it into account. It affects the measured length of the bullet, and bullet length is required for QL to do its calculations.
The Berrys hollow base bullet is longer, at 0.613". If that length was used for the calculation it would be misleading, because part of that length is air space. I did not use that length. The trick is to figure out how much space is in the hollow base, and subtract it from the bullet length.
Keep in mind that the hollow base simply displaces the lead. Imagine that you push/swage the lead at the base until it fills in the hole. The bullet's length shortens when you do this, because the lead is no longer displaced, and you now have a flat base bullet. The length of Berrys flat base 124 grain round nose bullet is 0.587", very close to the 0.486" of my box of Xtreme 124 RN bullets, and very close to the 0.590" used for the calculations.
We have to assume that the nose shape of the two bullets is roughly the same. It is to my eye, and the Berrys' bullets look very much like the Xtreme bullets, too, so the 0.590" is a pretty good approximation to use for the calculations.
Charge weights, pressure and velocity should be theoretically the same for hollow base and flat base bullets of the same weight, type and shape, i.e. both 124 grain, both plated and both round nose with a similar shape, if seated to the same OAL.
The Western data for Berrys 124 grain hollow base flat nose bullets and Berrys flat base round nose bullets in the 9mm are consistent with what is know about bullet length, OAL and seating depth. Note that the Berry 124 RN bullet is seated at 1.160" OAL, longer than used for my calculations, which will reduce pressure. The Berry 124 HBFN bullet is seated to 1.060" OAL, shorter than used for my calculations, which will increase pressure.
Western’s data shows a difference of 29 psi between those bullets when loaded with the maximum loads of True Blue. The pressure for the RN bullet is a little higher.
If I plug the Western data for 9mm Luger and True Blue into QuickLOAD, I get the following numbers:
124 FP (0.528”) at 1.060” OAL and 5.5 grains of True Blue = 27,329 psi
124 RN (0.590”) at 1.160” OAL and 6.0 grains of True Blue = 28,080 psi
The difference between these values is 751 psi, the pressure for the RN bullet is higher.
QuickLOAD’s estimates are not wildly different, since one can get a 751 psi difference by changing the powder weight by 0.1 grains of powder or less. e.g. adding 0.1 grains of True Blue to the 124 grain RN load (now 6.1 grains), increases QL’s pressure estimate to 29,287 psi, a gain of 1207 psi.
I found that the pressure for the flat nose bullet loaded with more Titegroup was higher by 4,584 psi. Keep in mind that our OALs were not as extreme as those in Western’s data, so I don’t think QL’s estimates are unreasonable.
Standard disclaimer: I cannot guarantee the accuracy of the estimate or the validity of QuickLOAD’s calculations. Use this information at your own risk.
