Q. So are heavier rounds dead for self-defense purposes?
Not really, no.
In fact, some more recent work suggests that some heavier, lower velocity rounds are superior in terms of wound ballistics. Current tests of newer, magazine sized 75, 77, 87 and even 100 grain rounds show faster yaw in ballistic gel and much more dramatic fragmentation than M855. Some 75gr open-tip (i.e., JHP) match bullets have performed very well in law enforcement use over the past 5 years or so. Additionally, 77gr open tip match bullets seem to be performing very well for the US military in combat operations since September 11th. Also showing great promise is the 87 gr P.R.L. match round.
77grain Match King Open Tip in calibrated ballistic gelatin. Note the long neck prior to tumbling, however.
100 grain Black Hills in calibrated ballistic gelatin. Note the amazingly short neck before tumbling (1 inch) and the dramatic fragmentation along with almost 13" of penetration.
Some of these heavier bullets, probably because of their length, maintain their fragmentation down to below 2100 fps and as a result have a much longer range of fragmentation, out to as far as 300 yards.
The flip side is that these heavier bullets will require at least 1 in 7" twists for proper stability, are more expensive than 55 gr. FMJ, and some types aren't widely available as of this writing.
Some of the heavier bullets can offer superior performance, but at an increased cost. In the meantime M193 is probably still your best bet for bulk defensive ammo. Do take note: this does not mean that all heavy rounds are good terminal performers. Bullet construction is far more important than pure weight or velocity.
Perhaps most promising, however, is the 77 grain Nosler NATO loading from Black Hills. (Not to be confused with the 77 grain Sierra Match King which has a longer neck). This particular round has a very short neck, high fragmentation and wonderful muzzle velocity.
Fact: Black Hills loaded 77 gr. MatchKing bullets have already seen extensive combat use by US military special operations units over the past several months. Additionally, there are reports that the Hornady 75 gr. TAP has been successfully used by certain U.S. military units for the past few years.
Opinion: Some reputable testers have described the Black Hills 100 gr. round as the "most impressive performing .223 round we have ever tested." Unfortunately, despite excellent close-range performance, this experimental bullet was dropped due to concerns of over-pressure loads and "rainbow-like" trajectories at ranges beyond 100m.
Fact: From a 16" barrel the 77 grain round tested above was still at 2400-2450 fps at 200 meters--and still fragmenting. The 100 grain round was still fragmenting at 2100fps at 200 meters from a 16" barrel.