Hi thanks for answer, yes you're right, something's wrong... Bolt has just this morning answered me that the barrel of my M4 thread is 14mm and that not all the 14mm accessories fit due to producer's tolerances... but that's annoying.
What I am testing are these, my M4 and this generic 14mm low quality silencer you see.
As soon as I get home I might send you more specific measures you need.