My former agency did that nonsense for a while. The department purchased several9mm Colt carbines. In the same era, we also purchased a launcher for use with impact munitions. These weapons were considered so dangerous and complex that only sergeants and shift OIC's were authorized to use them (because supervisory rank conveys sharpshooter ability).
This was somewhat complexing. After enduring numerous lectures how I should be a supervisor rather than a worker, suddenly I was both a designated marksman and aa grenadier.
The Beltway sniper case smartened the department up when we realized we were potentially outgunned. Botach International immediately replaced shipped out 5.56 Colt rifles on our promise to send them the carbines. The department trained non-supervisory personnel and I was even praised that rifles not be assigned to sergeants (though I made the point we should be allowed our own.
I think H8Train and I work the same A.O. If I'm correct, his department firearms training unit has traditionally been pretty conservative. Indeed, as semiautomatics became popular in law enforcement, a firearms instructor presented an in-service class on how terrible those things were and why we were better served with revolvers. Allegedly, after retirement, that instructor went to work for SigSauer.
That said, concerns about reliability would be a valid reason to ban magazine extensions. Given the other thread on what mag extensions we trust, there is clearly a concern about which magazines actually work.
Truth be told, I experimented with magazine extensions for my .40 SigSauer 226. Offhand, I don't recall what flavor they were. Adding a few extra rounds to a twelve round magazine seemed like a good idea even when I started out with a revolver. Nonetheless, I had a concern that the different grip might compromise my accuracy at the moment of truth. I never carried them on the street and they lived on my plate carrier. When we transitioned to the FNS-9, the weapon's dubious reliability and seventeen round magazine banished any though of magazine extensions.
I will remark that, if an agency approves magazine extensions or after-market magazines, they should be a specific brand and model and installed and/or inspected by an armorer or instructor.
The county executive does hate his department's evil black uniforms which, to his mind, were chosen to intimidate people and because George Floyd. The cost of replacing them would have been pretty expansive. I know the executive had hurt feelings when the cop-hating county NAACP chapter and the even more cop-hating "justice coalition" told the media that while they demanded this, that, and the other kind of "reform", they felt changing uniforms was a waste of money.
My agency only allows Glock mags. Issued mags are Glock OEM 15 round mags. Mag extensions are approved (I forget which brands), but both the approved extensions, and Glock OEM mags, must be max capacity of 24 rounds. The stated reason for the 24 round max capacity, is concerns about reliability of the higher capacity mags.
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"Whom shall I send, and who will go for us?" Then I said, "Here I am. Send me." - Isaiah 6:8
I haven't tried the OEM 24 round mags, but have been using the 19 round '19X" mags. I was using TTI extensions, for 20 round capacity, but have heard of, but haven't experienced, problems with the springs being weak and causing malfunctions.
The TTI mags have joined my 21 round P-Mags, for use in USPSA.
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"Whom shall I send, and who will go for us?" Then I said, "Here I am. Send me." - Isaiah 6:8