Two things:
1) The sandman flash hider is 2.7” long. Most AR barrels have (approximately) .5” of threading. That puts a 13.7” barrel at 13.2”. Add 2.7” = 15.9. Now with enough shims you would probably get to 16”, but you give up some thread engagement.
2) the actually length of the 13” BCM handguard is 13.375” at the 3 and 9 o’clock positions. This would possible put the shoulder of your barrel inside the hg. Now with adding the flashhider it is possible that your suppressor would be able to attach but it would be close.
Just a couple of things to ponder before you start spending money
1) The sandman flash hider is 2.7” long. Most AR barrels have (approximately) .5” of threading. That puts a 13.7” barrel at 13.2”. Add 2.7” = 15.9. Now with enough shims you would probably get to 16”, but you give up some thread engagement.
2) the actually length of the 13” BCM handguard is 13.375” at the 3 and 9 o’clock positions. This would possible put the shoulder of your barrel inside the hg. Now with adding the flashhider it is possible that your suppressor would be able to attach but it would be close.
Just a couple of things to ponder before you start spending money