I was looking at my FSB and it is probably straight but I'm obsessive compulsive when it comes to this shit and I cant help but think that it's canted a few degrees. Now, I went to the range yesterday and zeroed my red dot. It ended up sitting on the same line as my front sight post when cowitnessed. My rear sight is at mechanical zero. If the front sight was indeed canted, wouldn't the dot be to the left or right of the post when cowitnessed under these conditions?

Thanks,
Steven

Did you sight in your iron sights independently?  

A few degrees is significant and quite noticeable.  A half of a degree is not.

eta:  What barrel?

No I could not zero my irons because I couldn't find a front sight tool and didn't feel like taking the time to learn the shell casing trick because I was paying $10/hr.

ETA: The point is that my irons are not zeroed so any cant should be revealed by the dot being off center of the front post, If I am thinking about this correctly. I am only talking about windage here obviously.

You're good.

You don't need a front sight tool. Use the tip of a .223 bullet to depress the front sight post detent and rotate the front sight post. It's not as quick as the tool, but it's worked for generations.

Now, go shoot your irons and see if they're close to zero. Adjust accordingly. If your front sight is canted noticeably, your rear sight aperture should be way left or way right. A few clicks of windage isn't excessive.

"It ended up sitting on the same line as my front sight post when cowitnessed. My rear sight is at mechanical zero. If the front sight was indeed canted, wouldn't the dot be to the left or right of the post when cowitnessed under these conditions?"

You just about answered your own question and stop being so self avowed anal, just shoot and have fun. If the red dot is on target at your determined range, and the irons are also at that same aiming point, then they are aimed at the same place. It's not rocket science. Try the irons at the same range as the sighted in red dot and tweak them IF required, but from what you say they are now both GTG at that distance....<><....:)

The preceding post is I think nibbling around the edges of this concept.

As of now:

1. Your weapon is zeroed with a dot sight

2. When you look through the sight, the dot is above the front sight post.

3. The rear sight is mehcanically zeroed.  

All you need to do is go a few steps farther.

4. Set the weapon on a solid rest so it is fairly secure and won't move as you switch between looking through the sight or slighlty lower through the iron sights.

5. Set the red dot on target, without moving the rifle look through the iron sights.

6. Adjust the iron sights as needed so that the front sight post is centered in the rear sight and the top of the front sight is on target. (rinse and repeat 4 and 5 as needed.)

The iron sights will then be pointed at the same point of aim as the dot sight and for most practical (short range) purposes, you will be zeroed with the iron sights.  The difference in height above the bore will introduce some minor differences at longer ranges, but most people won;t shoot well enough at long range to notice.

Once you are zeroed with the iron sights, if the rear sight is still roughly in the center, there is no significant cant in the FSB.

+1. I usually sight in the iron sights first, then the red dot. Once irons are sighted in, I just adjust the red dot to be right on top of the front sight when looking through the rear sight and the red dot and the front sight. Its that easy. Sounds like you are already there to me. Just take it out and prove or disprove your irons at this point.