DoglegArms
Silencer Dealer of 2015, 2016, 2017
Here I go with a half baked plan and someone has to come along and ruin itI guess this one is going to need some more thought- I haven't measured the 10.5 from the bolt face yet. If I'm remembering correctly, the NFA barrel length is measured by inserting a rod against the closed bolt to the end of any permanently attached parts.
Yup.
"The ATF procedure for measuring barrel length is to measure from the closed bolt (or breech-face) to the furthermost end of the barrel or permanently attached muzzle device."
https://www.atf.gov/firearms/docs/atf-national-firearms-act-handbook-chapter-2/download