AR 15 front sight base cant

[andrewj]

My new AR's front sight base is canted to the right (while looking down the sights). I haven't shot it yet but it looks like it may be pretty significant. Do I just have to shoot it first and wait to see how she holds up? Is there a way to fix this without having to redrill new grooves?

I am quite the perfectionist so I HATE the thought of fixing the problem by clicking the rear sight over to compensate.

[Blue]

Is it a Blackthorne upper?

[andrewj]

Is it a Blackthorne upper?

Colt HBAR

I had to install the base myself and used one existing groove for one of the pins. I then had to drill the other groove. Somewhere along the way I misaligned or something.

[popeye4]

You could do one of the NM mods for the front sight base: drill and tap the pin holes and use small hex head set screws to hold the base in whatever position you desire. Loctite the base when you do the final assembly.

This mod will allow you to set the front sight to permit centering of the rear sight when you're on zero.

[ar15barrels]

Colt HBAR

I had to install the base myself and used one existing groove for one of the pins. I then had to drill the other groove. Somewhere along the way I misaligned or something.

So you installed a front sight base from ANOTHER barrel on this barrel?

That's you problem.
Front sight bases are NOT swappable.

[andrewj]

So you installed a front sight base from ANOTHER barrel on this barrel?

That's you problem.
Front sight bases are NOT swappable.

Apparently

[ar15barrels]

When a barrel assembly is made, they mount the barrel and the front sight in a fixture to drill both the front sight forging and the barrel at the same time.



There's no standardization as to exactly where those holes get drilled as the FSB is not something that's ever replaced.
The military armorer's manual states that if the fsb is damaged that the whole barrel assembly gets replaced.

I have a drill jig that aligns the fsb on the barrel while drilling, but it's rarely possible to re-install a fsb on another barrel.

[andrewj]

Problem solved

[maxicon]

Details?

[technique]

Colt HBAR

I had to install the base myself and used one existing groove for one of the pins. I then had to drill the other groove. Somewhere along the way I misaligned or something.

from my experiences, Colt FSB come canted...I have had 5 thus far. If you re-drilled and its still canted, get a clamp on gas block.

[technique]

-or-

http://www.bravocompanyusa.com/AR15-Front-Sight-F-Marked-p/front%20sight%20base%20-%20f.htm

a FS that you mate to your barrel...note the holes are not drilled.

[andrewj]

Details?

from my experiences, Colt FSB come canted...I have had 5 thus far. If you re-drilled and its still canted, get a clamp on gas block.

I was going to resort to a different type of block if the problem persisted but with the help from a leather mallet, I got it straightened out.

[popeye4]

I was going to resort to a different type of block if the problem persisted but with the help from a leather mallet, I got it straightened out.

Ah, yes, the tried and true "get a bigger hammer" solution.....

[JTFPEST]

What about aliginment of gas tube? Did it get out spec at the chamber end and gas key still in straight ?

[andrewj]

-or-

http://www.bravocompanyusa.com/AR15-Front-Sight-F-Marked-p/front%20sight%20base%20-%20f.htm

a FS that you mate to your barrel...note the holes are not drilled.

I went with the pre drilled base becuase I figured the grooves were quite uniform on most, if not all, AR rifles. Hell, my pre drilled/grooved Romanian AK barrel needed a front sight base and it went on without a hitch. If a eastern European country could get uniformity and interchangibility out of their rifles, I figured a U.S. made rifles would as well.

What about aliginment of gas tube? Did it get out spec at the chamber end and gas key still in straight ?

It was slightly askew as well. It had a little bit of strain on it since the barrel nut teeth had to straighten it out to get through the gas tube port in the receiver.