tango_down,
Just remember that if your looking for a LEO weapon (One that would fit the current bans configuration), the weapon has to come in the assault weapon configuration from the factory (C-2). You can't start off with a post ban rifle, then add/change items to make it into a LEO configuration (even if the bare receiver is stamped LEO).
Also, any LEO weapon is going to need some sort of department letterhead, so think form 5 on a semi LEO SBR (marked LEO). Your going to find that the 16" barrel on the HK-94 is a bit too long for service work. Then, before you leave the department, have the barrel pressed out, install a new 16" barrel, then have the C-2 take the SBR off the NFA books (leaving it as a LEO only weapon). This way, when you retire, the rifle is yours and off the department’s records, but in the mean time, you have service working weapon that will suit your needed (LEO weapons can be gifted, even with the folding stock, it’s the SBR (barrel) part that would need to be changed before the department can gift you the weapon on retirement).
Also, as stated, the only receivers that I am aware of in 40 are the MP5/40. Since once a machine gun, always a machine gun, and your department will not sign off on a Full-Auto’s, you may have to start looking at another platform for your LEO 40. Maybe an Ar-15 from Oly in 40 may be your weapon of choice.
Or if you want to go 223, then have Jayson build up a LEO V-53/93. Being that he can LEO build the weapon, you can have it any way you want (even SBR'd).