AR-15 Front Sight Pins

[Hoby]

Hi guys, new to the board and have a problem already. I recived a M-4 barrel today and it's not drilled for the 2 front sight pins. Any idea's on best way to go about it.

[Rex]

Can't help you. I think those are tapered pins, correct?
But I'd suggest you check out AR15.com.
I bet that has come up several times there. I know that some uppers for a while shipped with canted front sights and had to be corrected, lots of discussion about that.

[Hoby]

Thanks Rex, I found that site and your right alot to read.

[Gunbuilder]

Hoby,
I seem to remember something about a reamer. And in order to get it right for you rifle you need to have everything aligned and then ream/drill the holes for the sight in place.

Thanks,
Paul

[ctrmass]

I just thread some holes from the bottom of the front sight base.
For a range gun it works well. If it's something that's going to get hard use and you may need to depend on it in a life or death situation, I'd go for the taper pins.
I've seen drilling fixtures specifically for this purpose, but I cant remember where.
I suppose it wouldnt be a hard job to do with a fixture, proper size drill bit and taper reamer. Assuming you have a decent drill press.

[ctrmass]

Edit:
These arent the ones I was thinking about, but might put you on the right track.

http://www.bravocompanyusa.com/Armorer-Tools-s/67.htm

[kletzenklueffer]

Midway USA sells the taper pin reamers. Supplied by AR Stoner. The position of the pins isn't uniform, as one FSB will not likely line up on a different barrel from the one it was drilled on. I was headed down this road before and ran in to the issue of how to keep the FSB oriented on the barrel without rotating and causing the front sight to cant. Perhaps it can be tightened enough in a vice to friction clamp in place without cracking. I saw a photo online of FN Manufacturings AR assembly line and they had a jig that held everything in place. It didn't appear to be a production piece, but a one off piece made by/for them.

[GeorgeGaskill]

Are the holes already drilled in the sight base? If so, they will be cut oversize if used to guide the taper pin reamers. I think it would be better to at least pilot drill the holes on a milling machine so most of the material is gone when you run it the reamer.

If you have to drill the sight base, then it should work OK to be cutting the barrel at the same time.