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Canted front sight post


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This is my first post so bare with me. I recently had two PSA complete uppers (CHF barrel type) that required windage adjustment to the extreme left. I called customer service and they sent return labels. After about a two week turnaround they were back and each was within approximately 4 clicks of mechanical zero. I marked the barrel, front sight post, and upper receiver to identify whether those parts were replaced or not. They weren't. My question is how did these items get straightened out and is this something I could do from home?

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If you have a standard M4 style carbine, the front sight base(FSB) was probably canted to one side a little.


They probably just had to knock the FSB pins out, straitened the FSB and knock the pins back in.


It is something you could of done yourself. But you really need an FSB block, hammer, punches and a couple gunsmith levels. It can be done without the block, but its a PITA.


If you have a free float forend, the tube was most likely canted. Youd still need some specialty tools to fix the problem.

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Friction. Those pins can be a pain to get out sometimes. Theres always a tiny bit of slop between the pins and the channels. The taper on the pins are to insure theres a tight fit. The FSB just wasnt perfectly inline with the barrel/upper when it was pinned.


Id throw a bunch of rounds down range and see if your POA/POI shifts at all. If not, your good to go. Keep in mind that diffrent ammo, even the same weight, can/will have a diffrent POI.


I hope everything works out for you!


If you have any other questions feel free to ask!


Oh, and Welcome to the Armory!

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Another possibility is that the index pin may have been off center in the index notch of the upper receiver, under the barrel nut. The notch can be staked, and the threads chased to turn the barrel slightly in the receiver to bring the sights into alignment.

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