Yeah, it's completely up to the agency. Most have an armorer, and many small agencies have only one. I'm the armorer at my agency.
You could benefit from the operation of rebuilding M16 and M16A1's into modern carbines...
They'd need barreled uppers, less BCG's (I use the existing BCG, replacing the old rifle extractor spring), and collapsible stock assemblies. Plus whatever optics and BUIS they want, slings, rails, lights, etc.
The paperwork would remain the burden of the agency. In addition to the acquisition forms, there must be an annual inventory of all LESO property. It's not difficult, however, and the advantage is $100 surplus rifles. (That's the cost in LA anyway. It varies by state.)
I'd obtain quotes incorporating 10.3" to 11.5" 4150 chrome-lined barreled uppers from several manufacturers and then pick from the results. I recommend lightweight or gov't profile barrels.
Short barrels can also be obtained through LESO (and cheap) but the process is tedious and more akin to "digging through the DoD's trash bin". You never quite know what will turn up in a search (most of it is junk) and anything shorter than a M4 barrel is quite rare. M4 and M4A1 SOCOM barrels are common in RTD (DRMO) though, so odds of finding a serviceable batch of 14.5" barrels is actually rather high. They'll cost the agency about $18 per barrel.
(Don't count on finding any flat top uppers though. I got really lucky after 2 years of constant searching.)
The M4 barrels can be shortened, as they are not under modification restrictions. So, if you have a lathe, you could charge for turning them down and threading, plus an inspection and TE gauge beforehand.
I would definitely use new carbine gas tubes. Plan on having to replace some of the small parts as well during an M16A1 conversion. Most agencies will want to render them semi-automatic-only for patrolmen, so that's a $10 AR safety swap. The agency must retain all the weapons' original parts.
Idk if going the LESO route interests anyone, but feel free to email me if I can help. There are optics on RTD too, but good ones are uncommon. Determining condition is the most difficult part of the whole process. (That's not applicable to the weapons themselves, which are always in excellent to like new condition). We got a dozen Aimpoint CompM4's for $30 each. I like finding the stuff, but if they're all about
right now, it's better to go commercial.