AR15 upper assembly question

[Koda]

is it possible for a complete upper assembly to be put together so the barrel is not coaxial with the receiver resulting in a rifle scope running out of elevation for a standard 100yd zero sight in?

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[solv3nt]

is it possible for a complete upper assembly to be put together so the barrel is not coaxial with the receiver resulting in a rifle scope running out of elevation?

No. Use a 20 MOA base or similar.

 

[Koda]

No. Use a 20 MOA base or similar.

Im not long distance shooting. I updated my post to clarify...... I cant even get a 100 yard zero with a scope. I cant even get it 2" below bullseye at 25yds... everything is way low and the scope runs out.

 

[solv3nt]

Im not long distance shooting. I updated my post to clarify...... I cant even get a 100 yard zero with a scope. I cant even get it 2" below bullseye at 25yds... everything is way low and the scope runs out.

LOL well then..... Anything is possible really.... Who made the upper, and is it possible the barrel is bent?

 

[Lasers]

Pics?

What scope. Seems odd

 

[2Wheels4Ever]

It could be a few factors. Bent barrel, bad scope or out of spec scope mounts could also be possibilities. Is the top rail parallel to the barrel?

 

[Koda]

To answer some questions.... the upper is a complete Palmetto State Armory upper assembly. This one to be exact: https://palmettostatearmory.com/psa...er-with-mbus-sight-set-bcg-ch-5165448415.html

The scope is a UTG 1-8x28 Accushot. I had it on my other upper assembly and it zeroed fine. I replaced the scope mount with a new one but same problem. I dont suspect its the scope since it worked fine on my old upper assembly.... but anythings possible.... I know its a low end cheap scope but how could a scope designed for an AR15 just suddenly go bad like that?

 

[Kruel J]

I suspect it's the optic. UTG scopes are not good. Virtually impossible to have an upper/barrel issue that you describe.

Try a completely different optic and mount.

 

[Koda]

I say it's the optic. UTG scopes are not good.

I know they are cheap scopes but Ive barely shot this scope and don't have any reason to suspect its bad, it zeros fine on my old upper receiver assembly. The new PSA upper is literally brand new and thus the new part of the equation.
If someone can assure me an upper reciever build cannot be assembled that far off Id be more inclined to suspect or replace the scope... but I don't want to spend the money on a quality scope if the rifle build is bad.

 

[titsonritz]

Your upper receiver or barrel/barrel extension would have to be way out of spec for something like that to happen. UTG scopes do not inspire confidence.

 

[Member 34319]

Top of a receiver to the bore on a flat top, IF IN SPEC, is 1.215"

Add rings and the offset between center of bore and center of ocular shouldn't be much more than 2-3". Most decent scopes have 10-20 MOA worth of adjustments in either direction (20-40moa all together from one extreme to the other).

If your scope completely bottoms out and your not anywhere near paper, you did something horrible incorrectly, or the equipment is not of good quality.

 

[Kruel J]

I know they are cheap scopes but Ive barely shot this scope and don't have any reason to suspect its bad, it zeros fine on my old upper receiver assembly. The new PSA upper is literally brand new and thus the new part of the equation.
If someone can assure me an upper reciever build cannot be assembled that far off Id be more inclined to suspect or replace the scope... but I don't want to spend the money on a quality scope if the rifle build is bad.

Can I vote for a quality optic on a quality build?

Seriously though, I've never heard of a receiver being that far out of spec. I would think the barrel wouldn't even mount properly if that was the case. Maybe take the whole thing to @Velzey and see if he can figure it out.

 

[titsonritz]

Can I vote for a quality optic on a quality build?

Seriously though, I've never heard of a receiver being that far out of spec. I would think the barrel wouldn't even mount properly if that was the case. Maybe take the whole thing to @Velzey and see if he can figure it out.

The rail itself could potentially be out of spec, I would think that would be easy to tell though.

 

[Koda]

Top of a receiver to the bore on a flat top, IF IN SPEC, is 1.215"

Add rings and the offset between center of bore and center of ocular shouldn't be much more than 2-3". Most decent scopes have 10-20 MOA worth of adjustments in either direction (20-40moa all together from one extreme to the other).

If your scope completely bottoms out and your not anywhere near paper, you did something horrible incorrectly, or the equipment is not of good quality.

I dont have a proper way to accurately measure the 1.215 but thats good to know. What I can measure seems good (pic). Im estimating my scope is about 2.9" above the bore.... Id have to look up the total MOA adjustments of the scope and somehow compare with the calibers trajectory and scope height.

 

[Kruel J]

Just based on that pic it looks pretty good. The rails and handguard are lined up and indexed properly. At least from what I can see.

 

[Koda]

The rail itself could potentially be out of spec, I would think that would be easy to tell though.

is it possible the barrel threads are not concentric, or the barrel or reciever face is not perp? Or maybe some debris got in there during assembly?

 

[Koda]

Can I vote for a quality optic on a quality build?

absolutely... id love to spend the money on one but not until I find out if this new PSA upper is good. What I hear is PSA is just an average quality product... not that they are bad or poor quality just that this isnt a high end build.

 

[Kruel J]

is it possible the barrel threads are not concentric, or the barrel or reciever face is not perp? Or maybe some debris got in there during assembly?

Those are some pretty rare issues and hard to determine. Trying a different optic, to me, is the next logical step.

 

[msgriff]

The receiver face can be off square from the receiver bore/rail plane. It happens. I would contact PSA before attempting any disassembly.

 

[titsonritz]

is it possible the barrel threads are not concentric, or the barrel or reciever face is not perp? Or maybe some debris got in there during assembly?

Anything is possible, but that would be an extreme case. I would also suggest trying another optic assuming you have something available, even a red dot.