PSA 20" upper shooting low

[bellavite1]

So I got me this 20" classic rifle kit from PSA.
Once everything was assembled I found out that it shoots several MOAs low, to the point that I had to screw the front sight post all the way in just to zero at 25yds.
I will take the barrel off, clean everything and reassemble to torque specs.
Is it possible that the barrel is somewhat canted downwards in the upper receiver?
That would be a first for me...
Any suggestions to make sure that things are correctly lined up when I put it back together?

[Erni]

I think there were two different front sight bases heights? But I could be Mia remembering stuff.

[ray1970]

I also can?t remember all of the details but I know there are two front sight base heights. One for an old style carry handle receiver and one for the newer flat top receivers. I honestly can?t remember which is taller or shorter but if you have the shorter one you might need the taller one. I think the one for the flat top has an F mark?

[Wulf202]

sight base with different upper does seem like the simplest way this could happen

[bellavite1]

I also can?t remember all of the details but I know there are two front sight base heights. One for an old style carry handle receiver and one for the newer flat top receivers. I honestly can?t remember which is taller or shorter but if you have the shorter one you might need the taller one. I think the one for the flat top has an F mark?

This is the rifle.

FSB is F marked.

As with all PSA rifle kits the upper came completely assembled, so whatever it is was fucked up at the factory.

I could leave it like this (BUT IT BUGS ME!) or I could send it back, but chances are that they will just send me another one randomly picked from a shelf.

Plus the tinkerer in me wants to fix it myself...[Coffee]

94501

[battlemidget]

Good lookin rifle. It would look better with a carry handle IMHO. Buy some spare front sight posts and put the grinder to work?

[bellavite1]

Good lookin rifle. It would look better with a carry handle IMHO. Buy some spare front sight posts and put the grinder to work?

Yeah, I have done that, but it would still bug me...You know, OCD and all that shit...
I have also tried a MBUS instead of that UTG rear sight I have now, but it still was shooting low.
I even tried a scope, previously zeroed on a different AR, same thing, lots of adjustment was needed to zero it.

[Scanker19]

If it were me I’d start with a new front sight post, even if it were 10 MOA off, that’s a measurement on a post that probably isn’t discernible to the human eye without something to compare it to. Maybe. With PSA pricing it’s plausible that it’s just an out of spec post? I think they may even make taller ones for this specific instance.

Edit: a shorter post. Seems like 20” uses a shorter post. I’m willing to bed that since a majority of PSAs upper are 16” carbines they bought one kind of post and used it on all since they’re all Fmarked.

https://retrorifles.com/m16a2-m4-square-front-sight-post-short-or-tall/

Then I’d send it back if it bugs you that much. I personally wouldn’t take it apart until PSA looks at it incase that voids a warranty or something.

[bellavite1]

If it were me I’d start with a new front sight post, even if it were 10 MOA off, that’s a measurement on a post that probably isn’t discernible to the human eye without something to compare it to. Maybe. With PSA pricing it’s plausible that it’s just an out of spec post? I think they may even make taller ones for this specific instance.

Edit: a shorter post. Seems like 20” uses a shorter post. I’m willing to bed that since a majority of PSAs upper are 16” carbines they bought one kind of post and used it on all since they’re all Fmarked.

https://retrorifles.com/m16a2-m4-square-front-sight-post-short-or-tall/

Then I’d send it back if it bugs you that much. I personally wouldn’t take it apart until PSA looks at it incase that voids a warranty or something.

Well, I'm giving this short post a try.
Thanks for the link, I'll keep you guys "posted" (pun intended).

[Great-Kazoo]

. Measure your front sight, then rear. If the picture you took isn't at an angle. You can see the height difference.

The original fixed handle M16 & M4 used a front sight that did not have the "F" stamp. When they came out with the removable carry hand the rear sight was a tad higher then the fixed handle. So rather then reduce the carry handle height they decided to just use a front sight that was a tad higher. So the "F" stamps means its for removable carry handle M16/M4s.

94626

[Oscar77]

What kazoo said............ he nailed it.
If your FSB is "F" marked its for a flat top............so yes switch it out................ GTG.