What's the best way to remove the sand inside the FSB gas port as well as in the bore and chamber?

I've gotten 2 barrels from Bushmaster so far and they've always been covered with some type of sand in the nooks and crannies.

I've found that the cans of compressed air (like those used to clean computers) work pretty good at getting rid of small shit like that. When I cut down my FSB I had lots of shavings all over the place. The can of air worked real well.
Like this one:

Pick'em up at radio shack for a few bucks.

Gene

brake cleaner

That sand is probably glass bead blast material. I had a Oly barrel with that same material embedded in the FSP threads. Best way to remove is as mentioned above. Flush with some type of solvent i.e. break cleaner or better yet mineral spirits. Then blow dry with compressed air.

I use shop air from a blower and then I flush it with carb cleaner. Then more air, then I run a few patches of CLP through the bore because I don't like to have carb cleaner in my bore for more than a minute. Finally I wipe down the entire barrel with a light coating of CLP.

Some guys use a blower and a deep sink with warm water and a little dish soap, which also works very well. You need to thoroughly rinse the soap out and then take the blower to it until it's dry. Of course it will need a few bore patches with CLP and a CLP wipe down.