first, you can NOT install a birdcage device on a post-ban anything. the batfe has long ago ruled them to be a type of flash suppressor, not a brake.
the birdcage 'style' devices with the modified or blocked slots are as close as we can legally go on a post-ban firearm.
when you say "4 pins" are you referring to set screws or dowel pins?
if you are talking about set screws, the bbl. should be countersunk to give the set screws a mechanical locking geometry when tightened. loctite (threadlocking compound) should be used on the set screws, also.
if you have a threaded muzzles, any muzzle devive must be welded on to the muzzle (180° minimum circumferential weld), 1100° silver soldered to the bbl. or blind pinned to the bbl.
if your muzzle is smooth, jbweld, devcon and kantseize are all good choices to fill the gap.