Patchy

So i was thinking about making my own 6" barrel extension for my m4. I couldnt find anywhere on dimensional tolerances other than the diameter of .810 and thread pitch of 1mm. Would anyone have information on this or know where to look? Much appreciated

And thank you ?

I was told that because the barrel is shorter it increases the risk of unsafely swaying the barrel around...

I found briley barrel extension. But i could not find a definitive answer as to which style of choke would fit the m4.

Hi. I got my benelli m4 h20 a few months back and i absolutely love using it at the clay ranges. After going to a certain sporting clay range a few times, ive just been told i cant use my m4 because the barrel isnt 24". Has anyone used a 6" extension before? Is it worth the $? Because it was a disappointment that i cant use my first/only/favorite shotgun at clays anymore. Ive found a few online, but ive been trying to also find actual stores i can go to to see and purchase it. I am in Los Angeles but willing to travel a fair distance. Much appreciated.