M16s and M14s are limited to a number of weapons equal to about 20% of the full time commissioned officers in your agency. If you incorporated yourself as a "city", it might entitle you a stripped lower. You also have to be a particpant in the 1033 Program to have access to any of this stuff.
There is a lot of paperwork, and it is a real pain in the rear to get a used M16. Wait time for an M16A1 is about one year. M14s are supposedly about 3 months, but it has been 3 months since I submitted an M14 request, and while it was approved, they still haven't shown up. We also have to pay "inspection" and shipping fees of about $100-200 per weapon. For all of the bother, it is probably better to go through the other DOD surplus program that lets LE buy weapons from the military. Prices and wait time for M4s aren't worth it, but an agency can get M16A1s in about three weeks for about $360.
If we wanted 1911s, though we could get a bunch.
Where this really pays off though isn't in the high-speed stuff like rifles and NVGs, but in the high-dollar stuff DRMO would just scrap, like cars, computers and cameras. We have probably gotten about $100K worth of gear over the last year or so, and most of it was high-tech gear for our computer crimes guys and crime lab. The "tactical" stuff, while nice, is a drop in the bucket.