My recent experience with squib loads is unfortunately quite extensive. Although not in a combat environment, it was in one that attempted to simulate combat conditions.
I had loaded about 800 rounds of .45 ACP with 200 grain SWCs over 5.0 grains of Bullseye. I needed the ammo for a close-range gunfighting course I took. Although I randomly spot checked my loads, I missed discovering that about one round in every 15 or so was a squib with insufficient powder to launch the bullet or cycle the slide on my 1911. Apparently I had left powder for too long in my powder measure in a damp environment (my basement), and powder was clumping and bridging in the powder measure and not flowing well.
So there I was on the line with about 25 other shooters using Tupperware hearing all kinds of noise about 1911s being inherently unreliable. (Assistant instructor: "We know that 1911s will not feed LSWCs." This nonsense after 32,000 rounds of SWC through that weapon). You can do TRB all you want with a squib and get nowhere. I didn't tumble to the real problem until in total frustration I attempted to load a magazine of Hydrashock 230s and they wouldn't go either, because of the SWC lodged in the chamber throat. You can't see the squib unless you look down the barrel from the muzzle. And who teaches to stick your pinky up the chamber to check for a squib in combat?
In a semiauto handgun, a squib means that the bullet usually lodges at the chamber throat. Standing with a number of other shooters blasting away effectively hides the sound of the squib in the general racket. And frankly, if one is not particularly recoil-sensitive the lack of recoil goes unnoticed as well.
The squib effectively prevents the chambering of a new round, thus preventing a KB. Ties the gun up real quick though, and TRB is a lost cause. In combat, this means run, hide, draw a second weapon, etc. In other words, you're effectively screwed when pressed for time, as the weapon needs to be field stripped and the bullet pushed back out from the muzzle with a ramrod in order for it to be returned to service.
With this kind of potential problem in mind, I have never considered my reloads (or reloads assembled by anyone else) safe for defense, and always carry a quality factory product for that purpose.
Rather than tediously unloading each round with an inertial bullet puller, I opted to run the remaining suspect ammo though my M1917 revolver. Squibs were pushed back out with a ramrod with the cylinder open. The hazard here is that the much-touted "just pull the trigger again on a DA revolver if you get a misfire" will just align a fresh round under the stuck bullet. Bad juju: KB/bulged barrel, etc.
When shooting DA revolvers quickly, it is very, very hard to stop that second stroke if the gun goes "click."
