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Posted: 2/9/2006 2:26:38 AM EDT
Anyone know what tap to use in the front sight of the basic AR15?

Mine is a bit hard to turn and would like to remove and retap the housing so it will turn easier. Thanks.
Link Posted: 2/9/2006 2:59:33 AM EDT
[Last Edit: 2/9/2006 3:01:25 AM EDT by Gregory_K]
Did you try to turn it with the plunger removed?

If no try it. If your using a bullet tip to move the sighte it will be under spring tension. If your using a tool, they usdally rub the sides of the FSB a tab causing hard movment.
Link Posted: 2/10/2006 11:57:31 AM EDT
BTT

I have the same question: what thread pitch for the front sight post?

It is a new, unassembled barrel -- no detent has even been installed yet and a sight tool is the only way to start a post, but with so much resistance that the threads are flattening.

Cheers, Otto
Link Posted: 2/12/2006 12:30:17 PM EDT
[Last Edit: 2/12/2006 3:14:32 PM EDT by T-Ray]
8-32 per the "Competitive AR-15, The mouse that roared."


Wait a few hours before you proceed and I will check my source.


As usual I screwed up by going from memory. The correct thread size is 8-36 as said below.
Link Posted: 2/12/2006 2:30:41 PM EDT

Originally Posted By T-Ray:
8-32 per the "Competitive AR-15, The mouse that roared."


Wait a few hours before you proceed and I will check my source.




Do NOT use a 8X32 tap!!! That is the wrong tap and you will permanantly ruin your front sight housing by tapping it with it. It is a military tap, 8X36. They are not that easy to find, you probably have to go to a machinists supply or Brownells to get one. You will not find one at your local hardware, Lowe's or Home Depot.
Link Posted: 2/12/2006 4:19:29 PM EDT
Thanks for the replies, Folks.

Lacking the right tap, and not keen on spending money on something that really shouldn't be "broken" (a brand new Colt barrel), I improvised.

I took an old FSP, used a fine file to taper the threads a bit (about half its length but still enough bite to avoid cross-threading), and using the front sight tool and some "cutting oil" I ran it all the way down by the "half-turn and back-up" method. I then used CLP on a Q-tip and cleaned out the loosened parkerizing gunk that seemed to have filled in the threads a bit in the first place. I ran my makeshift tap a second time and re-cleaned the threads.

After that a new post went in with slightly more than finger pressure resistance, and it assembled without incident. All is well.

RRA223, that method may work for you too. If you don't have an extra FSP, you can probably do this without filing anything in that yours is already assembled and moves. Take it apart (remove the detent & spring) lube it well and run the sight post all the way down, clean, repeat. But use a real front sight tool -- the bullet tip thing won't do it, and needlenose vise grips will surely mess up the post.

Cheers, Otto
Link Posted: 2/12/2006 11:07:57 PM EDT
[Last Edit: 2/13/2006 12:32:02 AM EDT by RRA223]
Brownells sells the tap for 10 bucks or so (8-36 tap).

I took it apart and measured the tap, it's a 8-36 if any one needs to know.

My problem was the housing was dragging on the body of the front blade. I took my dremel and rubbed down the outside (FSP) and it turns nice now with a few drops of clp on the threads. A spray job of flat black finished it up and looks and works fine now. Thanks for your help, should have done this sooner!
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