Why switch? Allow me a diatribe about what I call "The Great Caliber Debate". Some may agree, some not.
Most of us have both 9 and 40 (and .380, 22 and 45). I went thru a period of time where I considered converting my .40 pistols. Or selling them. Then logic prevailed. There's really no reason in my opinion to abandon .40 caliber.
It makes no difference to me what the FBI decides to use for duty weapons. I am not in law enforcement. Their standards and studies may be important for people who carry a badge, but are pretty much meaningless to me. We have all seen the copious gelatin test videos on the web. While this is kind of stuff is interesting for those into the science of shooting, ballistics, etc. It really doesn't mean doodly squat to the everyday, practical aspect of self defense.
In a self-defense scenario, if you train properly it doesn't make a nit of difference if you are carrying a 380, an 9mm or a .40 cal. Most self defense ammo in these calibers are pretty good at doing the job they were intended for: Neutralizing a threat. To illustrate this point,
"But a .380 wont properly penetrate a heavy jacket" Really? Do not try this at home. But if it is a concern just aim a little higher.
I'll go on. If you dont want bullets going thru drywall and hitting the someone in the apartment next door, buy frangible or other ammo designed to minimize penetration. BTW: If a round goes thru the drywall it means you missed the bad guy. Aim every shot and own every round. In short, train more
.
Military standards for firearms and ammo are also a whole 'nuther thing. Not much in common with the average citizen's self-defense requirements.
I don't imagine myself being in a scenario where I have to take down a bad guy with a rifle who is wearing armor. I guess it could happen but I don't plan or train for it.
On the range or in a match, shoot what you have and enjoy. Or upgrade to a better pistol. There are some awesome prices now on new and trade ins of high quality .40's from Sig and others.
That's my two cents. Ok. Maybe it was six cents. But in my opinion selling or converting a .40 to a 9mm makes no cents.