Eh, I have to get in on this somewhere. Might as well be this post.
Just how is over-penetration worse with a 9mm FMJ than a .45 FMJ? The .45 ACP 230gr FMJ will penetrate 26"+ in gel, and gel has been proven to correlate well with human bodies. I have seen very few ambulatory people (I have seen one, just today, actually. The individual weighed roughly 600#) that have more than 26" in their torso, even from an oblique.
Further, yes, at ".45 velocities", many rounds are reliable expanders. This isn't the 70's.
Cartridge : 230 grain Speer Gold Dot Short Barrel (part #23975).
Firearm : Recoil-operated handgun with 3.8" barrel length.
Calibration : 10.0 ± 0.05cm and 591 ± 0.500 ft/sec impact velocity.
0.620 ± 0.0005" average diameter, 14.3 ± 0.031" penetration, 775 ± 0.500 ft/sec impact velocity.
-From Brassfetcher.com
I do agree though, use what works with your weapon, but then again--I don't agree. The weapon is chosen around the bullet, not the other way. That pistol isn't the point of the excercise. Putting a bullet into the target is. The pistol is just the messenger--it's the message that we are concerned with. If your pistol won't run a good JHP, screw it. Buy a pistol that will. Too many people worship the platform to the point that they will run sub-par ammunition just to justify the use of that platform.
Another point. That .45 FMJ-RN isn't making a .45 size hole. It is making about a .3" hole. Tissue is elastic, RN ammo only creates a permanent cavity roughly 66% as large as the projectile. JHP's make a permanent cavity rough;y 80-90% as large, due to the sharper shoulder on the front of the expanded projectile. A truncated nose design is good, and will probably increase the permanent cavity size over that of ball, but it won't exceed original calbier, that is for sure, so you are still stuck with a wound track 50% or less the size made by a good JHP. So for every time you shoot the target with a JHP, it will take two shots from the FMJ (or more) to cause equivalent tissue damage...that's what you're thinking. Again, wrong. Using simple math and the area of a circle, etc. the difference is 3-400% or so with regards to tissue crushed. Find the area of a circle .3" across and compare it to that of a circle .6" across. So to destroy an equivalent amount of tissue equates to 3-4 trigger pulls. Lame.
Stop whining about "Oh I'm scared the JHP will underpenetrate". Plenty of premium JHP's will penetrate 14-16" in .45 caliber. If 14-16" isn't enough for you, then why not? Are you worried about intermediate hard barriers? Then you shouldn't have picked a .45. Again. Pick the caliber to suite the need, and the weapon to suit the caliber. So many people are doing it all backwards and they end up with opinions like "Hardball is best because it's the only thing that's reliable".
It may be best--in a pistol that won't run. But why own such a thing?