The dimensions of the Freak inserts can be not so accurate - it is bassicaly only trade marking - .001" = 0,025mm. In the common industry you can not manufacture things so accurately... commonly you are fine when you have accuracy +/- 0,05mm = +/- .002". Even common measuring instruments are not able measure so accurately. You need really good reason for better accuracy and paintballs are not such like reason.
JJ Ceramic is great barrel, very quiet, at least comparable SP AA which is commonly a lot expensive. But JJ is medium bore (17,5mm) and the AA is small bore (17,4mm). Small bore is better to today common paint I think. But it is question if is that problem for you. Commonly is such like difference not problem for common player- the barrel has accuracy is the same, he has only little smaller efficiency, what is "problem" maybe only for Stock Class markers on 12g.
...but I have find that the number of holes in JJ Ceramic is still unsufficient for optimal silencing - there is still small muzzle blast even on decently tunned pumps (not on excessively tunned Stock Class markers). But you can double the number of holes on JJ very easily on common drill press - use the existing holes (they are here in three lines - 60°) like guiding case / bushing and drill new holes trough, from inside. When you drill from outside, you do not need clear the splinters whitch came when the drill goes out.
I have modifiet my 16" JJ Ceramic
in this way and he is now comparable with sillencer - on 25 meters no one will hear the shot and the impact of the ball is louder be even on closer range, so for the opponent is really hard to find from which place came the shoot.