I'm going to mount the FSB on the barrel in the Century kit today.

We will take pictures of each step, and give an explanation along with it.

This is kind of the hillbilly method, and can be done on a drill press or mini-mill.

1. See if the FSB will slide on barrel, if not, sand /file barrel journal until a tight fit (tapped on with mallet) is achieved. I like it really tight so the FSB doesn't shift when drilling.
  If you make it too loose, you can use locktite to hold the barrel in the proper position. (it must cure overnight). Or you can take a pointed punch and dimple the area under the front leg to create a tighter fit.


2. Time up the FSB on the barrel. I'm using the calibrated eyeball method today (because I don't have a fixture). I mount the barrel to the receiver for this, and keep it mounted the whole time so I can check for shifting of the FSB.

In my experience, I have found that I get the proper zero with the FSB canted slightly (1/2 degree maybe?)  to the right. If I have it top-dead-center, it will shoot to the right, and I'll have to crank my rear sight to the left to compensate. All my GI barrels seem to have this cant built in.  YMMV

Make a mark with a punch or dremel on the underside so you can check to see if the FSB shifted during the process. Once you've drilled and reamed you are committed.


I also take a marker and put some lines on the side for back-up


3. Mount the barrel in a solid vise. I used v-blocks, but you can also use wood blocks made at home. Leveling the part is very important (on both planes) I used a gauge pin and a bubble level. Not the most high tech, but it is what most guys would have. Make sure to support the backside, so it doesn't cant the barrel in the vise.  BRD's fixture would be preferred.


I also checked the FSB as well as I could with a smaller pin. Not precise, but it helps avoid an oops.


4. Because a drill bit will walk away from the barrel's radius (when using a pre-drilled FSB) , I flatten out the bottom of the hole with an 1/8" end mill.


Then I drilled it with a #31 drill bit. The small end of the 2/0 taper pin is .125", so you want to use a slightly smaller drill bit. Use lots of oil or cutting fluid. And blow the chips out of the hole.


5. Then I hand reamed the hole with the 2/0 spiral flute tapered reamer. Again, cleaning off the reamer and blowing out the hole often. Go slow, and check the depth of the pin before reaming more.


6. Leave at least an 1/8" of pin sticking out because it will go deeper when tapped in. You can always ream it more later. This pin hole needs to reamed a little more.



I ALWAYS DO ONE HOLE AT A TIME. That is; drill, ream, and finish pin the first hole before I even start on the second. This will keep the FSB from shifting on you and having your pins reamed at different angles.

7. This is where I stopped on the first pin. (before tapping it in) It proved to be a little deeper than I would have liked.


This is the difference in the finished depth after both were tapped in. Luckily, I found another pin in my parts box that was slightly different, and when installed was not as deep.


8. Sometimes, you will not come out on the backside exactly where you wanted. The angle can be slightly off, or the drill walks away from the barrel steel because its harder than the FSB. This is a cosmetic issue that is avoided by using an un-drilled FSB (the preferred method). I have never really liked using pre-drilled FSB's for this reason.


9. The FSB was taken off the barrel, and the barrel was plugged and parkerized. The FSB was not.



10. Then the rifle was reassembled.

tagscribe

Mike installed a demilled/once installed FSB (from the Colt M16A1 parts kit) on the non-slotted U.S. made barrel included in the parts kit. Taper pins (included in the parts kit) were used for the installation. The installation turned out well, as expected. The barrel subassembly was then disassembled, and the barrel blasted and parkerized. The parkerized barrel was then assembled with the FSB, front handguard retainer, and the A1 flashhider. This subassembly was then mounted to the Colt A1 upper with the barrel nut, and the slip ring assembly, followed by the handguards. An NDS-16A1 lower was put together with a semiauto fire control group and M16A1 kit parts and pinned together with the upper assembly. Mike will post pictures as time allows. We now have a semiauto A1 rifle built from a NoDak Spud lower, Colt M16A1 parts kit, U.S. contract manufactured barrel, and semiauto only fire control parts.

Harlan
NoDak Spud LLC

BTT for the pics.

The cant would be about the width of a front sight post, sometimes more. It depends on the barrel and upper.

I've seen upper receiver forgings that are warped to one side. So this affects it also.



First off let me say that I hate, no loathe, rear sights that are adjusted all the way to one side.

I have had to re-mount several barrels in uppers to get the FSB to go different directions. Depending on if I want the rear sight to go left or right to get to center.


If you use the barrel clamp method, the receiver will follow the barrel nut when you tighten it. (this is generally better, and will have your FSB canted to the right)

If you use the receiver clam shell, or Panther Claw,  the barrel will follow the barrel nut when tightened. (which can make the FSB go to the left)

I would use a center drill instead of the end mill to start the hole.

Then just drill and ream as before.

An un-drilled FSB just makes it so much easier because you don't have to worry about the drill walking away from the barrel (which is harder than the FSB) in the hole.

Straight pins can be used, but I would drill the hole instead of the "notch method' you describe.

Drilled holes will be even, cut grooves will have voids with no contact. Which can lead to slop, and looseness in the long run.

Harlan went to the range yesterday and shot it.

Functioning was fine (no gas issues), and he only had to go one click to the left of where I had centered the rear sight.

He also shot a group that was around an inch at 50 yards off the bench. Which is pretty good for his eyes.

All this makes me happy.

Here's the final group after zeroing.

50 yards
Iron sights
55 gr. V-Max factory load
Century 1/9 twist barrel

You may be able to get a 0/0 tapered pin to work in that hole. It's the next size up.