Kindly excuse my ignorance.
This is about the ammo selection and FBI seems to settle for 9 mm for various reasons and I am sure that they would have done a proper analysis before settling on the same.
Now here in India .38 pistols are easily available and at a reasonable price. Though the ammo is not so easily available and quite expensive where available.
Therefore, is it reasonable to presume that the best caliber in India is .38 ACP and that is comparable to the one used by FBI??
Please note that I have no intention of busting your chops here. I'm just trying to inform you.
I'm not sure what you mean by ".38 pistol". When talking about ammunition, terminology is very important as there are many similar names.
Inadvertantly interchanging some of these cartridges, could lead to injury and in some cases could have fatal consequences for the shooter.
The .38 ACP is considered to be 9X23 and is not commonly available. I have never seen it at any gun store. Do you mean .380 ACP instead?
I don't know about the "best" caliber but the FBI looks for a minimum of 12" of penetration in ballistic gel.
They also would want to use a projectile that expands properly
9mm Luger is 9X19
9mm Makarov is 9X18
.380 ACP is 9X17
On paper they seem very similar but in reality, there is a big difference between the two ends of the spectrum.
Two of the popular choices for concealed carry in the USA are 9mm and .380 ACP. However, I don't believe any law enforcement agency today would consider using .380 ACP as their official duty round.
Traditionally, people who were looking for a small, easily concealable pistols bought .380 ACP pistols or revolvers in .38 Special.
Today, however, there are many small 9mm pistols that are about the size that .380 pistols were ten years ago so there seems to be a move to shift from .380 to 9mm.
Certainly the 9mm compact pistols are selling very well and easily surpass the sales of .380 ACP pistols.
Some people consider .380 ACP to be marginal. For that matter, some people consider 9mm to be inadequate.
However, the chart posted in the article to linked to by Abhijit, shows very similar penetration with the most popular self defense cartridges.
9mm, being the most common pistol round here is the cheapest to purchase. It is way cheaper than .380 ACP and this is another factor in its popularity.
Here is an article that might give you some food for thought.
9mm vs 380 ACP For Self-Defense: Which one is Best?
Remember one thing; all pistol rounds are low powered and cannot compare to the power of a rifle round.
Here is a
list of handgun cartridges
In the indian context, pretty much any .38 caliber handgun round will be preferable to .32 S&W Long or .32 ACP which are the commonly available rounds there.