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Page AR-15 » Build It Yourself
AR Sponsor: bravocompany
Posted: 7/31/2014 11:10:57 PM EDT
I'm thinking just put on a standard front sight base and drill through the pin holes and install roll pins. Can you put set screws in a standard front sight base?
Link Posted: 7/31/2014 11:37:45 PM EDT
[#1]
As far as I know barrels aren't ever pre cut for taper pins. When a standard FSB is being installed, they drill through the holes in the FSB and through the bottom of the barrel.

I could be wrong though....wouldn't be the first time.
Link Posted: 7/31/2014 11:41:58 PM EDT
[#2]
Pinning a front sight base isn't a typical DIY project.  Front sight bases shouldn't be pre-drilled for the taper pins either.  And yes, you can put set screws in a FSB, although it won't be as strong a pinned block.  Another option is Armalite's clamp on FSB.
Link Posted: 8/1/2014 1:05:54 AM EDT
[#3]
YHM makes a folding clamp-on FSB.  I have one, you dont realize how nice it is being able to fold it out of the way until you try it.
Link Posted: 8/1/2014 2:00:42 AM EDT
[#4]
AASG,

I've pinned FSBs on four virgin barrels.  Two were McKay 20" pencils, the other were M4 barrels from wherever. I'm no machinist.  Only one of the FSBs was a virgin, too.  The others were take offs.  Patience and a steady hand are needed.  Of course right size drill bits, taper reamer, etc are required.  No problem.

Edited to add:  Super emphasis should be placed on getting the FSB clocked straight up and down otherwise the sights will have to be driven waaaay off to one side to get sighted in.

Ray
Link Posted: 8/1/2014 9:11:15 AM EDT
[#5]
Here is what you need OP:

http://www.bravocompanyusa.com/BRDE-Fixture-for-Drilling-Pinning-Front-Sight-Base-p/brdejig3.htm

Or send the barrel out to be pinned.

Or get just a clamp on base.

Link Posted: 8/1/2014 9:36:21 AM EDT
[#6]
I ran into this issue a while back. I didn't feel comfortable with it the first time so I set my a2 gb to the side and bought a clamp on. But now I've also successfully drilled barrels (both FSB's were already drilled, probably take-offs) just make damn sure of 2 things- 1- gas block is pushed back against handguard to line up gas port as far as forward-back goes. Then, make sure the front sight post is in EXACTLY the 12:00 position. Then clamp it down to barrel, double check, then drill.
Link Posted: 8/1/2014 9:40:09 AM EDT
[#7]
Install a low profile clamp on gas block and then go with a keymod kool aid rail system dujour.


Link Posted: 8/1/2014 10:46:18 AM EDT
[#9]
I'm swapping barrels, so I already have the a2 fsb, so I'm just going to drill straight through and install roll pins. probably a set screw first to hold it together while i drill.
Link Posted: 8/1/2014 11:33:36 AM EDT
[#10]
Pinned on FSBs are installed by putting a FSB on a barrel, drilling and reaming the two parts together to create a mated assembly.  They are not interchangeable parts.
Link Posted: 8/1/2014 3:40:51 PM EDT
[#11]
Here's how they do it at the factory. Scan is from the Black Rifle II book.






Link Posted: 8/1/2014 6:04:42 PM EDT
[#12]
A pre-drilled FSB isn't new.  It's a take-off.

Drilling the barrel and FSB is a one-time, first install project, and not for Wile E. Coyote gunsmiths.
Link Posted: 8/1/2014 6:26:59 PM EDT
[#13]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
A pre-drilled FSB isn't new.  It's a take-off.

Drilling the barrel and FSB is a one-time, first install project, and not for Wile E. Coyote gunsmiths.
View Quote

I'll prove you wrong.
Link Posted: 8/2/2014 4:16:35 AM EDT
[#14]
There are a number of challenges in drilling and reaming your own FSB pin holes in your barrel.  One of the first is absolutely guaranteeing that your old FSB is perfectly aligned with the barrel's gas port, which is a challenge with any gas block, but harder with a standard FSB because of the part's size and bulk.  Then you need the tooling - FSBs are usually installed with taper pins, so you need a reamer of the proper taper, and the pilot drill for that taper, and at least a good drill press to mount them in.  Do you have a machinist's vise to put on the drill press' table?  You'll need something very precise to keep the barrel and FSB in place and keep their alignment maintained while you do this.

The process isn't complicated: locate the FSB appropriately and keep it in place.  Mount the barrel/FSB assembly in your drill press solidly and accurately.  Drill the pilot hole perfectly centered on the FSB's first hole.  Now change to the taper reamer and ream appropriately.  Relocate for the second hole and repeat.  It's not the kind of thing you can do without good tooling and lots of patience for a first try - I wouldn't try one myself, but if you're bound and determined to do it yourself, study up, get good tools to make it work properly, and then take your time when you do it.  I'll be interested in your final product.
Page AR-15 » Build It Yourself
AR Sponsor: bravocompany
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