Thanks Striker, I always appreciate a compliment on my sig line
. It used to be specifically relating to caliber wars, but I figured I'd expand on it to make it fit all of these types of topics.
But, again, I think that some shooters profit much more from gaining familiarity with some guns rather than others--for some shooters, the increase in familiarity with a particular gun will result in very little accuracy improvement, IMHO, IMPE.
Why? I'm not being facetious, but that's the question you have to ask when you look at the benefit of gaining proficiency. Why would this training benefit me? Is that worth it over this other training?
In your scenario, we have a snub-nose revolver vs. let's say a fully customized 1911; grips are a perfect fit and it's capable of out-shooting anyone. Yes, if you anticipate needing the long range shot, it would be better to practice with that 1911. That's familiarizing yourself with two things - fundamentals of distance shooting and distance shooting with a 1911.
Now you throw in the snub. You may understand distance shooting better than you had before you practiced with the 1911, but you need to practice it with the snub to be proficient with the snub. Personally, if all you carry is the snub, I don't see a reason to practice with the 1911. If you mostly carry both, the snub as a backup, then very little reason to practice the distance shot with the snub. However, if you carry the snub as EDC, but the 1911 only some of the time, then you want to practice with both.
At least, that's my take on it. I think you should practice with what you use. It's why I don't, and will never own a .22. I also don't plan to take a shot at someone at a greater distance than any length in my house, so I have no desire to practice distance shooting.
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As to your scenario, there is one question, but people are breaking it into two:
1) Would you be confident in your ability to hit the target?
2) Would you be okay with the risks involved in taking that shot?
1 is purely a marksmanship thing, and a lot of people have said they would be confident at various ranges. This is almost the Practical Accuracy you were talking about, even though it is under the impression that the circumstances are beyond the paper target.
2, however, is where people get hung up. Especially in the scenario of an active shooter where innocents are near the line of fire. What is best for YOU is to escape. What is best for the most number of people is to stop this man. Can you live with what happens if you miss?
Personally, if I was comfortable that I could make a hit, I probably would take the shot. At least, that's what I'm saying right now - I don't honestly know what I'd do in a real situation because I've never been in one.