Ok, existing carbine, looking to form 1

I understand the form 1 process somewhat, only have done braced pistols.

Plan is to do 5.56 and potentially .300 BO--Do I list 5.56 as caliber, as I understand, "multi" is not acceptable and provided caliber is marked on barrel, calibers other than on form 1 are ok?

Overall length, stock extended with whatever barrel length I initially go with, if I have multiple uppers, no issue?

Picture, (2), serial number and whole gun, do I just do the complete lower or whole gun with 16" barrel?

Think that's it, I certainly appreciate it.

Mark

Just enter data for the original configuration. So 5.56 is fine. Whatever barrel length and OAL is fine.

You can change either at will with zero duty to inform.

Take a pic of just the stamping on the lower. Make/model/serial.

Excellent! thank you for the info.

now, have to decide on which one, haha