Okay, so winemaker now. But Boeing Machinist back in the day. You have machinist skills. You worked that profession, for Boeing.
You have the knowledge, experience, and training/work performance to accomplish this task.
Not asking you to modify a Tubb brake, not in the least.
I'm saying, you have a quest to find out if this theory works, and you also have skills that most people don't. Based upon those ASSumptions, you CAN buy a Tubb brake, and mic it all out - as a machinist, you know about precision measurement. Externally, you could buy that brake, copy it's dimensions - externally - and MAKE that thing to fit your 308 AR at 5/8x24.
At that point, you could test the $hit out of it, and report back.
You may only have a wood lathe and drill press now - but as a machinist, don't you know other machinists that have the macines that will accomplish this task?
There's rules on this site. Then, there's The Rule on this site. You jump into something and start asking specific questions about a product, and no other member HAS that product... then The Rule leaves it at this: You wanted the info, You asked the questions, and no one has it. At this point, You buy the product, test it, and You report back on it.
You're in that category with this series of debate, right now.
Get busy. You made the grade on this one... <thumbsup>
Or, just make excuses... <dontknow>