AR15 A2 style front sight alignment

[Epaphroditus]

Maybe I'm just anally retentive or OCD or nit picky or all of the above but, dang it, I don't like the rear sight being so far from center. I've tried several rear sights and even put them on backwards so absolutely certain it's the front sight that's off in windage.

I never assembled an upper before so not sure the best way to tweak the alignment to center up the front sight.

Any suggestions? How tricky is it to adjust the front sight?

[Rifle ronin]

Pics?
If its a front sight base, its usually pinned in place.

Maybe AR Barrels will chime in with ideas.

[r1ghtw1ng]

If it's a fixed A2 front sight block, you can't adjust windage. It might be slightly canted... there are some reports of PSA uppers having canted front sights. no easy fix that I know of.

[sigstroker]

Barrel might be clocked a little in the upper. How tight a fit was the pin in the upper slot?

[alpha_romeo_XV]

What kind of rear sight? Fixed carry handle, removable carry handle, flip'up ?
No easy fix for a fixed carry handle. There are some old threads on this.

[Epaphroditus]

Yup, PSA upper. Front site canted slightly. I can still zero but the rear sight has to be set a bit to the left - more than seems reasonable.

[G-forceJunkie]

Reasonable is the entire range of the rear sight. Thats why it is made that way. If you like it or not, thats its purpose. If it bothers you, you can remove the front sight base pins, bolt it up in a centering/drilling fixture, re ream the pin holes untill they clean up, reinstall the pins, oversize if necessary.

[tacticalcity]

I went down the same road with PSA. I ended up doing a credit card charge back...

Sadly this is the best option.

[SanDiego619]

No problem friend, now it is like AK47

AK47 shoots fine with canted sight

[ar15barrels]

Maybe I'm just anally retentive or OCD or nit picky or all of the above but, dang it, I don't like the rear sight being so far from center. I've tried several rear sights and even put them on backwards so absolutely certain it's the front sight that's off in windage.

I never assembled an upper before so not sure the best way to tweak the alignment to center up the front sight.

Any suggestions? How tricky is it to adjust the front sight?

Many AR type barrel/upper pairings do have some slop that you can adjust the FSB alignment within while you are assembling the upper.

[ar15barrels]

Barrel might be clocked a little in the upper. How tight a fit was the pin in the upper slot?

More often than not, when there is slop between the upper and the barrel, it's NOT in the index pin cut to the pin but actually in the reciever bore fit with the barrel extension.

[ar15barrels]

Yup, PSA upper. Front site canted slightly. I can still zero but the rear sight has to be set a bit to the left - more than seems reasonable.

Loosen barrel nut.
Twist barrel the direction the sight needs to move while tightening barrel nut.

[ar15barrels]

Reasonable is the entire range of the rear sight.

http://ar15barrels.com/tech/MIL-C-70599A.pdf

Check out 3.4.6 on page 9 of the PDF file.
5 clicks from mechanical center was the actual milspec.

Oddly enough, the newer 2009 specifications document no longer carries that requirement:

http://ar15barrels.com/tech/m4milspecs.pdf

[ar15barrels]

On another site, Randal wrote/posted about securing the upper, and using an extra large screw driver to twist the FSB.
The problem with that "fix" is that it bends or breaks the FSB taper pins.

I have had 1000's of uppers apart and have yet to see a broken taper pin which can be attributed to twisting on a FSB.
I have seen broken taper pins when someone installed a different FSB on a barrel without properly drilling/reaming the barrel, but that breakage happened during pin installation, not from twisting.

In the way that a taper pin is properly used to hold a FSB to a barrel with half the pin into the barrel and half the pin into the FSB, it's got WAY more strength than the 46,000psi double double shear strength rating that taper pins are specified for.

You would break the barrel index pin or the aluminum receiver long before the taper pin.

All that is happening during twisting the FSB is the barrel moves over to one side of the index pin notch and the extension slides to one side of the reciever.
Taking out ALL the slop to one side is usually enough to straighten any assembly related problems which usually originate from uppers assembled on reaction wrenches.

[alpha_romeo_XV]

White Oak Arms has their FSB with adjustment set screws and flats milled into the barrel so you easily get rear sight at dead center.