[bayonet14]

No - my 1st registered M4 lower on a paper Form1 I was able to list several calibers (1 typed in and the others hand written in) this was like 2005 - Under caliber you can list multi - on your length you want to list the shortest upper you plan to run on the registered lower (in my case I went down to 5.5" with a OAL of 26") - If unsure and want to ensure a 1st time go try to find out who the examiner is for your state to get the proper clarification.

Buy a lower that is registered as 'Multi' if you can - I would also go as far as get a forged and one that already had ambi controls while your at it

 

[bayonet14]

I love info graphs and pictures Thanks Jeremy!

 

[bayonet14]

You don't have to buy a multi caliber lower. Once you do a Form 1, you are the manufacturer registering the caliber.

There are lowers marked 'Multi' not say 5.56 or .223 - this goes back to what the OP had a question about .... and a lower already marked Multi would not be restricted to just 'one' caliber...this is good for several reasons and more so seeing how ATFTB has wordsmith several other clarification letters most of the time just making things clear as mud

Look - you want me to make your head spin... check this out - SilencerCo is releasing a new compact .45 suppressor and registered in that caliber only - you can change endcaps from .45 to 9mm - on a pistol suppressor that you can remove baffles ... this (again depending how you interpret law and what ATF says is a caliber change .... why you ask well because the endcap retains the baffles and thus by ATF is a caliber change + a silencer part...big NO NO.

Now you may argue well what about a rifle silencer in .30 caliber registered as such but I can change the endcap to 5.56? Well - by ATF that's ok because its not a caliber change of the suppressor (the guts cannot be removed) and the endcap is just that a endcap....not a silencer part...LMAO...your head hurting yet?

 

[bayonet14]

If the receiver was sold on a 4473 as a receiver then it can be built into a pistol or a long gun. If it was sold as a rifle receiver it can be SBR'd, but not made into a pistol. Once it goes from pistol status to long gun it must remain so.