I'm trying to install an FSB (A1) on my Bushmaster Superlight Barrel.  Problem is I can't get the pin holes to line up.  I can try and tap the pins in but they will not go in.  It looks to be off about a 1/16+.  Is this a problem with the FSB or the barrel?  Should I try something else?

Any help would be greatly appreciated.

Are you trying to install a FSB from a different barrel?  If so, it likely will never line up, as each barrel and FSB are drilled separately and as a unit and are unique to each other.  There is no standard spot where the holes are drilled and reamed, so the chance of a FSB from one barrel exactly lining up with another are very slim.

Installing FSBs properly is really a job for a proficient machinist, but a few here have had luck doing it on their own.

Quoted: Are you trying to install a FSB from a different barrel?  If so, it likely will never line up, as each barrel and FSB are drilled separately and as a unit and are unique to each other.  There is no standard spot where the holes are drilled and reamed, so the chance of a FSB from one barrel exactly lining up with another are very slim. Installing FSBs properly is really a job for a proficient machinist, but a few here have had luck doing it on their own.

Thanks for the help.  I'll see what the head machinist up here at work would say to do.

Here's the way I would do it, if all things were available to me:

First of all, you need some type of heat resistant, metal infused epoxy to fill in the original FSB holes/slots in the barrel.  Fill them in, let them cure and machine the profile back to the original dimension.

Set the barrel and FSB up in a mill so that the FSB is perfectly in line with the barrel indexing pin.  Clamp both in that position so that neither can move and drill and ream the barrel to the FSB existing holes, centering up on the holes as appropriate.  You need a 2/0 reamer to ream out the holes.  You may end up needing over sized taper pins, which can be made from any taper pin that will fit in the hole, just get them longer so that you can trim them to the proper length.

Not an easy process for the average DIY guy, but a no sweat job for a proficient machinist with the proper equipment.

I just had Kurt's Kustom replace my post ban Fsb with a pre ban unit.

Kurt could probably do this job blindfolded!

Quoted: Kurt could probably do this job blindfolded!

Only if he wants to lose a finger or two.