If i put 10.5 on form 1 and i would like to change to a shorter barrel later say a 7 in
what do i do

Supposed to just write a letter to the NFA Branch advising them of the change in description so they can update the registry with the current   barrel length.

Quoted: If i put 10.5 on form 1 and i would like to change to a shorter barrel later say a 7 in what do i do

If it is not a "permanent" change, meaning that you still have the 10.5" to go back to, then you HAVE to do nothing.  If you sell the 10.5", and permanently switch to a 7", then the NFA Branch requests a letter notifiying them of the change in configuration.

Write "under 16 inches" and "under 26 inches" for barrel length and overall length, respectively. I did that on mine with no problems. I also wrote in multiple calibers (5.56/9mm/6.8 in case I ever wanted to use a different set up)

Quoted: Write "under 16 inches" and "under 26 inches" for barrel length and overall length, respectively. I did that on mine with no problems. I also wrote in multiple calibers (5.56/9mm/6.8 in case I ever wanted to use a different set up)

The Form 1 is for MAKING and making it in more than one caliber, barrel length and AOL is impossible. Being vague like t"less than 16 inches" on the Form 1 is a crap shoot.  Some have had no trouble, like yourself, others have had their applications sent back adding a few weeks to the process.  All depends on who your examiner is and how they feel that day.

List a specific length and caliber as this ALWAYS works.  You may list additional calibers and lengths in 4h, but it's not necessary.

Quoted: Quoted: Write "under 16 inches" and "under 26 inches" for barrel length and overall length, respectively. I did that on mine with no problems. I also wrote in multiple calibers (5.56/9mm/6.8 in case I ever wanted to use a different set up) The Form 1 is for MAKING and making it in more than one caliber, barrel length and AOL is impossible. Being vague like t"less than 16 inches" on the Form 1 is a crap shoot.  Some have had no trouble, like yourself, others have had their applications sent back adding a few weeks to the process.  All depends on who your examiner is and how they feel that day. List a specific length and caliber as this ALWAYS works.  You may list additional calibers and lengths in 4h, but it's not necessary.

I used form 1 as well. I've heard rumors of it not working this way, but I've never actually found someone who said it didn't. You are right though, if you just put a specific number, it will work for sure - and as long as the change isn't permanent, you should have no worries either.