GRIZ, sorry... but some of your information is wrong.
The FBI officially adopted the 10mm in late 1989. S&W 10mms did not start being produced until 1990. H&K didn't produce a MP5 in 10mm or .40 until 1991. So, hard to work with guys in the 1980s using guns that weren't produced until the 1990s.
In regards to testing, if .45 was so applauded prior to 1986, how come it wasn't issued (even Thompsons were declared obsolete by that time)? Some agents were carrying semi-autos up through 1986, but after the shootout, the FBI allowed all agents to carry them (9mm SIGs) until their transition was complete (and also between the 1076 and Glock). It is weird, being 1911s were allowed for a lot of the early FBI years, in both .38 Super and .45.
In regards to revolvers used in the shootout, only one agent was allowed to carry .357 Magnum; McNeill (I'll have to check my books at home, but not 100% that he even loaded .357 Magnums). All other agents shooting revolvers were shooting .38 +P, including the two ankle guns and Mireles' revolver, who was the last agent to put rounds into the suspects. Mireles was carrying a 586, which is a .357 revolver, but loaded .38s per regulations. If you read Anderson's book on the shooting, there are a lot of personal accounts made by a few of the surviving agents that put it all into perspective... being "outgunned," "poor shot placement," and "calibers not doing the job." Mireles talks specifically about not carrying something that could result in his termination from the FBI.
I would also hesitate to say Mireles ended the fight... being Platt was probably bleeding out inside the car. Most doctors, looking at the 9mm wound that Dove is credited for, feel that if Platt surrendered right after that wound, and was rushed directly to the hospital... he still would have died. Mireles was probably running just on adrenaline, so nobody can fault him at emptying his revolver into the car, as he walked past his fellow agents, both injured and deceased.
In regards to the S&W 10mm series, I've yet to hear about or see cracked stainless 10mm frames, which is what all of them were built on. There were issues with the SIG style decockers, which were recalled (also were changes in the magazine followers during that time), but never was a widely accepted feature on Third Generation guns (these were most of the complaints, as well as a 9-shot stainless pistol not being the best for carrying in certain roles). I also wouldn't expect them getting the round counts of full power 10mm through them, moving to the lighter loading, and switching to SIG for a short period before going to the .40 Glocks in 1997... Owning a 1006, I'm definitely calling BS on that statement, as the S&W, while no longer supported by S&W, is known for taking true 10mm power like a champ. But if you have information that I haven't seen, by all means, share it.
The whole movement to 10mm was due to the results of 9mm in that shootout. Can't be cut any other way. When a slug stops short of a suspect's heart, even if it was a fatal shot (it was), and that person seriously injures three agents (another was slightly injured, and another was uninjured) and kills two... that is a problem.
At that time (mid-1980s), ammo technology wasn't what it is now. So a bigger bullet, with more energy (only mass and velocity are variables in that equation), was the solution. It was an identical solution back when the .38 didn't do the job against the Moros in the Philippines... which lead to the .45 ACP.
.40 works good for barricade penetration, so agencies will continue to use it. But if you look at wounds, 9mm (today) does a lot more closer to .40 or .45. All common handgun rounds are very similar with performance... stink. In actuality, the job of the handgun is to get you to a long gun. It is a compromise, you are losing cartridge effectiveness to gain the ability to carry it on your person. A .45/.40/10mm/9mm/.357/.38 isn't changing that... carry what you are comfortable with or what you are allowed/have to. The .40 discussion is always looked at using today's ammo, instead of what was available when it was originally introduced.
I like .40... because it is something different. I have two M&Ps in it (5" Pro and a Compact), as well as a SUB-2000 Gen 2 (takes the M&P magazines). If there is an ammo shortage, I'll still be able to get .40 when everyone is trying to stock up on 9mm or .45. So, yea... .40 sucks. Go get rid of those guns, and buy up .45. Try not to buy 9mm guns... those suck to, especially since I have a SIG P938 and S&W 642-1 converted for 9mm. I like carrying those, so help keep those two calibers in stock and buy .45.
Actually, I have a Glock 30S... so, the .45 now sucks, as well. Go with a .357 Magnum. Don't have any guns chambered in it. But stay away from .44 Magnum. Too little power... go .460 or .500 (seriously, .460 has a lot more versatility... as you can shoot .454 Casull and .45 Colt).