Any suggestions where to find a threaded barrel for the 3.6?

Fast forward to 2020, I have the same question

I am currently researching the subject and decided to post my findings so far:

1. It seems like Apex are planning to introduce the barrel in question in the "near future" (see comments at Apex Releases Threaded Barrel for 9mm M&P M2.0 Compact – Apex Tactical Specialties)

2. There is only one factory variant of threaded barrel for the M2.0 and it's a 4.625" (replaces 4.22" or 4.07" factory barrels). Unfortunately, there is at least one reports of that barrel not working in 3.6" gun (M&P 2.0 3.6" 9mm Threaded Barrel? : SmithAndWesson)

3. Based on lengths of the factory barrels, it seems like S&W "extend" their threaded barrels by .405". I am not sure how exactly S&W measure barrel lengths, but if we assume that 3.6" barrel is exactly 0.4" shorter than 4.0", theoretically (4.07" - 3.67" ~= 0.405"), we could just put a thread on a factory 4.07" barrel and try to use it in a 3.6" gun.

Now, I hope participant of this forum will help us with the following information:

0. Is it possible at all to put a thread on a factory barrel and if it worth the effort (It is possible to acquire 4.07" factory barrel for $62)

1. What is the exact length of 4.0" barrel when measured, let's say from the breach (using a dowel?) to calculate the exact length of a 3.6" barrel.

2. Can someone try a regular factory 4.0" barrel in a 3.6" gun?

3. Is it enough to apply a "Birchwood Super Blue" on the threads or one will have to apply Nitrite or Cerakote?