Is there an updated list of C&R transferable machine guns? The most recent list from the ATF is only updated to 2018.

Not to my knowledge, or at least none that have been actively updated and published. It's mostly up to sellers/dealers to determine the C&R eligibility of their machine guns now based on either acquired manufacture paperwork, serial dates, sending to the FATD, etc.

To put this into perspective though, it'll be 2023 in a handful of hours. That means an exponential amount more of C&R eligible Colt SP1's and other increasingly 'modern' firearms which is fairly exciting.

Everything registered in the 68 amnesty has been C&R eligible for a few years now as well

That’s an excellent point thank you!

Honestly, I think pretty much any machine gun should fit the criteria based on “Any other firearms which derive a substantial part of their monetary value from the fact that they are novel, rare, bizarre, or because of their association with some historical figure, period, or event.”

The trick is writing to the ATF and getting the determination of such.

It would be interesting to see the ATF argue that they aren’t novel or bizarre but then have to say they’re not in common use and thus can be effectively banned.

Completely stock colt sp1s are c&r. Doesn't a conversion to NFA remove that eligibility?

That depends mainly on when the SP1 was "re-manufactured" into a machine gun. Whenever it was converted becomes the new date it was born.

Not all SP1s are C&R and as mentioned, the date of conversion would be the new born on date.

But see my previous post about “which derive a substantial part of their monetary value from the fact that they are novel, rare, bizarre”

The government has created the inflated prices in an attempt to make novel and rare

As a C+R holder I never knew that !
Learn something new every day.

That has worked for some individual Group Industries BAR's

You are getting into the "all MG's are novel/rare/bizarre" argument (which I don't disagree with)

(but since I'm not the ATF) From the definition, only original unmodified SP1s are C&R.

Just for the sake of conversation

The ATF does not say anything about them being modified to full auto changing their C&R status but does say “Firearms which were manufactured at least 50 years prior to the current date, but not including replicas of such firearms”

I would argue an SP1 is not a “replica” of anything but is a semi auto AR. In theory, if an SP1 was manufactured and subsequently converted to full auto more than 50 years ago as well it would fall within the purview of C&R status.

Now if you had an SP1 that was manufactured originally in say 1964 and subsequently modified into a machine gun in 1984 I would say the clock starts ticking in 1984 since whoever converted it was the new manufacturer according to the ATF.

Like I said, just a thought exercise as of course the ATF makes rules up as they go along so who knows?

I guess whatever it is you have or are wanting OP then send a letter to the ATF and get it deemed a C&R and good to go. Nothing like getting machine guns delivered to your house bu the mailman!

Friend of mine made this argument several years ago when he tried to have lightening link number 1 registered as a C&R. The atf firmly rejected his idea. The reality is in 17 years the current registered machine guns will all be 50 years old.

I would argue that an SP-1 is a replica of an M-16.

Weird double tap

Conversion date is what matters.  Remember that it’s making a new gun, which is why they require engraving the maker’s info.

I’d agree that all MGs should be C&R due to that value from being novel and bizarre.  But politically, that WON’T happen.

That’ll happen in 2036.