First, a few tips:
- When discussing your plunk test results, you might want to specify working OAL or maximum OAL. I'm pretty confident the 1.095 you list is maximum, but I would hate to start talking based on that assumption, then find out it was actually 1.110 maximum, and that 1.095 plunk test result reflects a .015 reduction.
- When you say you found the bullet length for that data, that data appears to be for an unspecified 125gr JHP. How did you find the bullet length for an unspecified bullet? I mean, it looks like a Sierra 125gr JHP to me, but unless I could verify that, I wouldn't make any assumptions.
- When you are calculating seating depth, you might just want to use .750 for case length. What you listed -- .754 -- is the SAAMI spec, but very few 9mm cases are that long, even when brand new. Since you want to use one number, .750 makes the math easier in the event that you find yourself wanting to calculate a seating depth without the aid of a calculator or spreadsheet.
All right, so what I'm seeing here is (.750 + .654) - .1.095 = .309 seating depth. That is deeper than you typically want to be. The case walls definitely start thickening by .300 with 9mm cases of all manufacture. If the shank is seated deeper than that, it will start to bow out the case walls, or swage the base of the bullet, or both. You want to avoid those things. HOWEVER, if the base of the bullet is beveled, which is the case with this bullet, you can get your base seated a little deeper than .300 before that starts to happen. Not much, but .309 is doable with some cases. I seat the MBC 125gr SWC to a depth of .310 for my CZ.
NOW, you say that you loaded and checked a bunch of dummies, and every 1.095 passed the plunk test. Your data indicates those are very close to rifling engagement, and your normal variation from one stroke to the next should land some in the lands eventually.
I would load a dummy (resize, flare, seat, taper, crimp) to 1.11 and plunk test it to make sure you have your max OAL correct. If it plunks and spins freely, load to 1.13, plunk to verify it's too long, then start seating deeper and deeper until it plunks and spins freely. If you verify the max OAL without rifling engagement is, in fact, 1.095 and CZ with the shortest throat, then I would say this bullet is probably a bad option for the CZ and other short-throated pistols. You need a cushion, and if you knock off .010 and get that seating depth down to .319, that's just SUPER deep.
You asked about using JHP data. The answer is no. You use the closest data available. You match bullet weight first, and surface material second. Match coated or bare lead with lead data. Match plated with plated data (or to lead OR jacketed -- not both -- based on manufacturer recommendation, if no plated data exists). Match jacketed with jacketed data. THEN match profile third. If you have data for a jacketed 124gr RN and data for a jacketed hollowpoint, and you are loading a jacketed hollowpoint, use the data for the hollowpoint. The only time you would want to use jacketed data for lead is when there is no lead data available, period, and even THEN you would want to do a significant reduction of the charge window.
A seating depth comparison between two lead bullets of the same weight is helpful. A seating depth comparison between an LRN and JHP is self-deception.
Finally, and
VERY IMPORTANT, please weigh those bullets. Someone mentioned earlier that they look weird. To me, they look like they're not 124gr. In the picture with the Berry's RN, if that Berry's is 124gr, I can't imagine those coated bullets are also 124gr. The coated ones look huge. The more I look at them, the more they look like they're 147gr.
