Upper build complete troubleshoot irons HELP

[WilliamAnderson]

I finished my first upper build and had a gunsmith look over the head spacing. He said it was good to go.

I test fired it yesterday and 100% reliability.
I shot 30 rounds.

I'm pretty happy with it!

Just one little issue. The rifle was shooting a foot right from my point of aim with the irons centered.
My irons are magpul polymer front and rear.

I was able to crank my rear sight one hash mark over to the left to get on target. I was wondering what the problem could possibly be.

Any insight.

Upper build is a Odin works 18'' 3 gun barrel 1/8 twist wylde chamber.
Rifle length gas system. ALG defense EMR Rail. Cerro forge flat top upper. Nickle boron m16 carrier. A2 flash hider.

My rear takedown pin very tight. I have to use 16oz hammer taps and a punch to get it pushed out.

I know it's good to have a tight upper to lower match, but this is pretty dang tight.
Could it "flex" the upper to lower match, throwing the sights off?

could I have not torqued the barrel enough? I used the included wrench as per the instructions...

Thank you for your help.

[WilliamAnderson]

It is attached to the rail.

[russ69]

A foot to the right at 1000 yards is pretty close, just click it over one MOA.

[707electrician]

It's possible your rail is slightly canted

[pterrell]

1. What distance are you shooting at? 1 foot at 500 yards isn't too bad. 1 foot at 36 yards (where you typically want to BZO your Irons/Optics if you don't have a 300 yard range) is pretty rough.
2. Is it a free float rail or standard? If it's free float, you could have installed it with a cant or a skew to it. Set it on a flat surface as a reference and see how it lines up with the upper receiver. If it's a standard rail and you're using a traditional loop sling, it is possible that you're pulling it so tight that it is flexing the barrel entirely.
3. In my experience, my Magpul Irons are nothing spectacular. I would go get a carry handle and a standard A2 Front Sight Block, but then again I'm kinda old school I guess.

Your upper and lower being tight shouldn't throw your shots. Is your group tight? Are you sure that it isn't "you"? Even getting used to a new style and feel of stock can upset your natural point of aim and cause problems with your group. Pictures would help, as well as the information I requested.

[WilliamAnderson]

I was shooting at 100 yards. After reading your suggestions, I believe I need to have a second look at the rail. I thought my mind was playing tricks on me when it looked like the rail could be slightly rotated.
I'll post a picture soon. I'm going to re-mount the rail after I adjust the barrel nut.

[WilliamAnderson]

I had a 6 shot group at 2.5'' I think the accuracy could use work, but I was aiming at a 2/3 torso steel target. Not the best test of accuracy.