Trying to prioritize funds before a looming CO assault weapon ban
Currently have a full size MP5 clone
Looking for a K and maybe a 33?
Seems flats are not receivers..?
Presume I’d pay to have them built in the future (not sure I’m capable/trust my hand a building myself) - builder engraves S/n and transfers them back to me via FFL making my idea worthless as they will be banned at that point?

K flat

Talk to me like I’m 5yrs old

Can you not just slap a serial on the flat now and build whenever you want in the future?

Do PMFs even need a serial?  Assuming that you'd have to prove it was built by you before any ban you speak of actually happened.  Maybe you could just engrave and serial now anyway, take to ffl, have him 4473 it back to you for a paper trail?

*Not legal advice I have no idea. BuT wish you luck.

Flats are not legally firearm receivers until they are bent.

That said there is nothing that prevents you from adding a "serial number" to a flat if you want right now.

I think your challenge is going to be proof in the future that the firearm in question was actually a "grand-fathered" assault weapon under the law and getting somebody to complete a build for you.

An HK style flat.... even if bent and now legally a firearm receiver isn't technically an assault weapon unless it meets the legal description of a Colorado "assault weapon" as defined in whatever law may be eventually passed.   For example, if you look at the current Colorado house bill that passed it basically has to be semi-automatic firearm with at least some defining "feature" like a pistol grip, threaded barrel,  etc.  A bent flat isn't semi-auto nor does it have any defining assault weapon features.

Even if you bend a flat and add a serial # now, unless you can build the gun completely yourself in the future covertly via a cash purchased parts kit,  I highly doubt any federally licensed gunsmith is going to complete a build of a non-assault weapon flat into a Colorado illegal configuration assault weapon and transfer it back to you. Even then complete homebuilt guns may need documentation as existing in that configuration before the ban went into effect if you want to be completely safe from future prosecution.

If you really want a fully grandfathered assault weapon, I would personally buy complete HK style firearm from say PTR or Century that are known models by the manufacturer as "assault weapons" and have a 4473 showing transfer to you.

Overall this new proposed law really sucks. I am in the process of getting ready to potentially transfer a tons of guns to our place in Colorado so they are grandfathered in should the law pass.  Its like deja-vu all over again like it was in 2015 with magazines where I moved hundreds of mags and thousands of links to CO. to get them documented in State before the mag ban went into effect.

If you can afford to do so, I’d just pony up for a real deal German hk93. Short of that, I’d buy a PCS33K from Jeff Walters.

Re: the mp5k, it really doesn’t get any better than an SP5K-PDW and Arms Unlimited has them for $2850, which is a killer price.

FML, okay

So try to find something like this? in stock?
@jbntex

No. Zenith is no longer the importer of MKE. They make a completely US clone and they have a spotty reputation.

Buy an SP5K-PDW.

If the goal is to get a verifiable grandfathered Colorado "assault weapon" that would seem to fit the bill a lot better than a flat.  Its a known model from a major manufacturer that is semi-automatic and has a definable Assault Weapon (Pistol) ban feature being a threaded barrel.

However, it doesn't look to be in stock and I don't think Zenith is actively making MP5 variants right now.  They used to import them from Turkey which is what that blem barreled receiver looks like with its push pin and blocks arrangement.

If HKs are your thing bite the bullet and buy a genuine SP5k and a 93 (from Gunbroker).

If you’re asking the question you at least have the means for a clone but that doesn’t solve your lack of a 93.

I’d dig deep into savings and just get what I want, if I was in your shoes.

This.