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KBCraig wrote:FMJ will almost always feed more reliably, especially in older designs that predate hollowpoints. If you have any concerns about reliable feeding, then go with FMJ, Pow'Rball from Cor-Bon, or one of the new projectiles that combine an FMJ profile with JHP expansion.

When a round/caliber has sufficient power to both penetrate and expand reliably, then go with HP; if expansion is questionable, then go for penetration. In low-power calibers, LRN rules.

The projectile that combines an FMJ profile with JHP expansion is EFMJ (Expanding full metal jacket) from Federal.

The reasons for using lead round nose in small calibers include feeding reliability (small caliber guns are famous for being finicky feeders), deeper penetration (the cartridges don't contain enough energy to both penetrate and expand reliably, and if you can only have one or the other, penetration wins) and the possibility that if all the stars are lined up right, they may deform somewhat and create a larger wound channel (which will still be pretty small).

Here's the FBI's Report on Handgun Wounding Factors and Effectiveness. It doesn't directly address the FMJ / JHP question, but it does explain what bullets can and can't do, and what factors make some better stoppers than others.

The follow on to this was a set of test protocols to determine how different cartridges measure up to the criteria the FBI arrived at. The results of this testing were shared with the nation's law enforcement agencies, and virtually every one outside of the military (I don't know of any exceptions) carries JHP ammo today.

These are the guys that are most likely to need effective stopping power and put their lives on the line with this equipment every day. I don't think you'd be poorly served by following their example.