Canted front sight post

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[ARCHIVED THREAD] - Canted front sight post

Posted: 2/9/2020 1:59:05 PM EDT

Have a new colt upper that has just a slight cant on the front sight post...1 to 2 degrees maybe. Most wouldn’t notice probably but that kind of thing just bugs me. I don’t have access to a nice drill press but wondered if a tapered reamer could clean those holes up and then use an oversize taper pin to lock it down?
If not - who would you recommend to handle this kind of work?

Posted: 2/9/2020 2:02:46 PM EDT

[#1]

Oversize reamer/pins is an option.

If not comfortable DIY, JT at Retro Arms Works is solid.

Posted: 2/9/2020 2:31:54 PM EDT

[#2]

Those FSB’s are kinda tricky, because there’s basically no flat surface to align with or for a vise to grab. The last one I did is crooked, and it bugs me too :-)

I did hear a good suggestion that I’ll try next time. First tap the hole underneath for a set screw. Then go to the range, leaving the taper pins at home. Put the rear sight in the middle of its travel, and then adjust the front sight (using the set screw) so that the windage is correct. Then bring the thing home and drill/ream the taper pin holes.

Posted: 2/9/2020 2:40:26 PM EDT

[#3]

Posted: 2/9/2020 2:52:24 PM EDT

[#4]

Damn good DIY read HERE

Posted: 2/9/2020 4:15:34 PM EDT

[#5]

How do the sights work? Can you zero it without extreme left/right windage on the rear? You shouldn't be able to notice a cant if you can....

Posted: 2/9/2020 5:04:18 PM EDT

[#6]

How do the uppers feed ramps line up with the extensions ramps? If the sight is only off a degree or two it may be as simple as loosening the barrel nut and re-tightening it when the sight is straight.
As long as the bolt lugs still travel smoothly into the extension lugs, the barrel can be rotated slightly. The alignment pin on the barrel extension may or may not have some play with the upper receiver, which may be the reason the sight is canted to start with? Sometimes it may require thinning the side of the alignment pin on the extension or shaving the side of the alignment pin cut out on the receiver to allow the barrel to rotate?

Posted: 2/9/2020 5:08:20 PM EDT

[#7]

Quote History

Quoted:
How do the uppers feed ramps line up with the extensions ramps? If the sight is only off a degree or two it may be as simple as loosening the barrel nut and re-tightening it when the sight is straight.
As long as the bolt lugs still travel smoothly into the extension lugs, the barrel can be rotated slightly. The alignment pin on the barrel extension may or may not have some play with the upper receiver, which may be the reason the sight is canted to start with? Sometimes it may require thinning the side of the alignment pin on the extension or shaving the side of the alignment pin cut out on the receiver to allow the barrel to rotate?

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Was thinking the same thing. One can either file some from the slot or the pin to get the needed clearance.

Posted: 2/9/2020 5:23:43 PM EDT

[#8]

Quote History

Quoted:
Was thinking the same thing. One can either file some from the slot or the pin to get the needed clearance.

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:
How do the uppers feed ramps line up with the extensions ramps? If the sight is only off a degree or two it may be as simple as loosening the barrel nut and re-tightening it when the sight is straight.
As long as the bolt lugs still travel smoothly into the extension lugs, the barrel can be rotated slightly. The alignment pin on the barrel extension may or may not have some play with the upper receiver, which may be the reason the sight is canted to start with? Sometimes it may require thinning the side of the alignment pin on the extension or shaving the side of the alignment pin cut out on the receiver to allow the barrel to rotate?

Was thinking the same thing. One can either file some from the slot or the pin to get the needed clearance.

I was about to suggest if the barrel could be rotated slightly. If not I day just shoot it as long as it falls under Milspec it's probably fine.

Posted: 2/9/2020 5:52:28 PM EDT

[#9]

Is the post canted relative to FSB, or the FSB canted relative to upper?

Posted: 2/10/2020 6:08:41 PM EDT

[#10]

The problem is that while you should be able to zero the rifle at any given distance, when shooting closer/further your impact will move left/right as well as up/down.

Posted: 2/10/2020 7:31:47 PM EDT

[#11]

Have you zeroed the rifle to see if the rear sight windage is shifted appreciably?

If it is then thread a straight indicator rod of 8-12” long into where the front sight post threads. Level the upper receiver in vice blocks. Observe the cant of your indicator rod relative to plumb. Use a hefty leather mallet against the front sight tower to drift the barrel extension/pin clocking closer to true. There is usually a little leeway for clocking rotation.

Alternatively, leave it as is and test your sight regulation against appropriate KD targets from 50-500 yards. If you don’t run out of windage under typical conditions then it may not be worth messing with.

[ARCHIVED THREAD] - Canted front sight post

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