What does 6 rounds instead of 5 buy you?
We can look at some probabilities if we make some assumptions.
Let's assume:
1. It takes two solid hits to incapacitate an attacker.
2. Our hit rate is about what police see in their shootings--about 30%.
3. We get to use all the rounds in the gun before getting killed, or before getting injured to the point of not being able to resist further.
4. The attackers are determined--that is, they keep attacking as long as they are able vs. running as soon as they see a gun or hear a shot.
With those assumptions, what are the chances of achieving 2 hits on a single attacker with 5 rounds? About 47%. That is, about 53% of the time we would expect to fail to "stop" the attacker in the scenario we created.
What about with the same assumption but with 6 rounds? Now it's about a 58% success rate. We've gone from failing more than half the time to succeeding about 4 times out of 7 by adding one round.
If you go to assuming 2 attackers the odds are really terrible with either 5 or 6 rounds although 6 rounds does provide better than double the chance of success than 5. Not that it's anything to celebrate given that the chance of success in neutralizing 2 attackers with the assumptions above is only 7% with 6 rounds.
The moral of the story is that 5 or 6 rounds and real-world hit rates is a bad recipe for defending against one determined attacker, let alone more than one, but we can see that there is a significant benefit to having 6 vs. 5.
More on the subject:
https://thefiringline.com/forums/sho...d.php?t=494257