I have seen plenty of data on Mk262, TAP75, and M193. I have never been able to find comparative data to SMK 69. The 69 seems so out of fashion -- neither here nor there, but there must be tons of data on it somewhere.

Well I have a lot of the 69 Gold Metal Match and I got it for under 1/2 the price of Mk262.

So what would be better for defensive use -- SAAMI pressure SMK 69, or WinQ3131 M193?

These fragmentation charts should answer your question.

www.jobrelatedstuff.com/forums/topic.html?b=3&f=16&t=189353

The 69 should perform close to the 68 in the charts.

69 grain is better than M193 loads.  It used to be the FBI load.  It fragments at a greater depth than 68 or 75 grain loads so its inferior in that context.  Not suitable for 10" barrels due to velocity issues.  Its got a better chance of fragmenting because M193and M855 can fail to fragment even above the fragmentation threshold and this is not as great of a concern with match ammo with thin jackets.  You will also get reduced flash with the 69 grain load.  The 69 grain load almost never comes with  a cannelure and 68 grain always does.  69 tends to have greater % fragmentation than 68 but the long neck means 68 is the better choice. 69 is usually more accurate than 68 in most weapons.  Think that about sums it up. 69 was the first BTHP match round pushed for defensive use.  People resisted it before 2000 and would not believe it was superior to soft point an FMJ loads in the 90's.

So people resisted it, and now they would accept it if there was not 75 and 77 out which turns out even better.

Ok. I will assume 68 is better for my purpose.

One thing I am still confused on -- how come 69 is not good for short barrels, but 75 and 77 is the BEST for short barrels?

Quoted: So people resisted it, and now they would accept it if there was not 75 and 77 out which turns out even better. Ok. I will assume 68 is better for my purpose. One thing I am still confused on -- how come 69 is not good for short barrels, but 75 and 77 is the BEST for short barrels?

Good question.  

Also, most of the chrono data I saw showed that the 69 loadings were faster than the 68 loadings being shipped. So I figured that 1 more grain of weight plus more velocity would most likely be better.

I would think core alloy and jacket thickness would be the same within any given mfg's line for 69/77 grain offerings (Sierra, Nosler) and 68/75 grain offerings (Horn).  I haven't compared lengths, but I would also guess they are same length and the only difference being the amount of core within the jacket.  So if the heavier offerings consistently penetrate, rotate and fragment, I would guess the lighter offerings would behave exactly the same.  The only delta would be that the lighter offerings, having less mass, would penetrate a bit less.  Just a WAG though.

68/69 have a higher minimum velocity for their fragmentaiotion floor than 75/77.  At 10.5" and under you get almost no frag range to speak of with .223 pressure ammo with 68/69 grain ammo.  The 75/77 is moving more slowly but its min frag threshold velocity is lower still due to the greater stresses applied to the longer bullet and they end up with a greater fragmenting range even though they start off with a lower velocity.  If I were you I would contact Dr. Gary Roberts on tacicalforums.com in the terminal effects forum section and ask him for the specific details as he will have them on hand.  He also knows the minimum barrel length that will allow fragmentation at the muzzle of .223 pressure 68/69 ammo.

I know the 75 grain ammo was actually longer than the 77 grain ammo but they changed bullet design and I believe its about the same now.  As for length of projectile differences in 68 and 69, I have never measured the pulled bullets.