Originally Posted by
L-2
Regarding ".gov" changes, the prior Glock 22 for the FBI (whether any Gen4 models were issued, I don't know) lasted ~20 years.
I suspect the FBI will keep its 17M and 19M models for as long as possible or practical, unless something terribly bad results from this firearm platform.
One consideration is night-sight life being ~12 years. With the cost of a set of night-sights and the logistics (other unrelated maintenance parts, time, transportation, documentation, procurement) it becomes arguable to just replace the entire group of firearms.
Budget requests and the timing of such can take a committee to accomplish. Years can go by depending on priorities with firearms being passed over. I suspect nobody (in the FBI) is working on the next handgun project right now or yet. Getting something like this "right" the first time is very important. Can someone imagine, "We don't like the mag cut out notch and flared magwell after all. Let's just do it all over again and ask for another $85 million (in budget)."
To what extent there was overlap between the prior SIG P-series models is also unknown by me. Some large organizations do prefer to standardize rather than giving too many options when it comes to handguns. Prior to that, a short-lived 10mm S&W attempt; S&W 9mm 459, and revolvers.
SWAT/HRT (special teams) in an organization is different. It's smaller and due to tech advances and the political visibility of these units, can get things faster and changes implemented faster (more agile is good terminology). From my recollection, SWAT and HRT personnel have used the Browning Hi-Power, SIG P226, and Springfield-Armory "Professional" 1911(s), with Glock in there, too.
This is all from my recollection from just an informal study as I've not worked or had much contact with them at all.