The mininum shoulder for warranty is .100 period.

So 1/2x28 needs .600, 5/8x24 needs .725 etc.

No warranty or any troubleshooting from me under this mininum, 14 years full time and .100 shoulder or greater have had ZERO misalignment issues ever. Any of the only handful of issue I have ever had are people cheating this basic min shoulder.

Had some idiot years ago make a thread saying I messed up his AK barrel with 14mm threads that was only .570 thick.  Thats a 3 human hair thread, hope he never reproduced.

This is industry standard and most actually require thicker shoulder than that.

Adequate shoulder is far more important than concentric threads, I fix 20 or more bad jobs a month from other people by adding clearance and recutting the shoulder.

Any warranty issue must be sent back to me to repair or replace, ZERO will be done if its not sent back to me.  

This is standard in every warranty in all industries, if my GMC truck fails it must be taken to a GM approved repair facility. If my John Deere tractor messes up and I take it to Jim Bob tractor repair, Deere will laugh hysterically at me if  I ask them for money.

Scratches or finish marks.

While this is extremely rare the barrel must be shipped two times, clamped in a machine and spun at 800rpms for 45 min.  Great care is taken, but scratches can occur.

I won't be refinishing anything or paying for anything if scratches occur.   Most factory finishes I can clamp as physically hard as I can and ZERO marks will occur.  It will depend on how good your finish is, a crappy duracoat job or hydro dip I can scratch with my finger nail....