Hello;
1st. AR, went with PSA .300 supplied with M-BUS flip up sights and added a Sig Romeo red dot so I can co witness with the two.
On iron sights do I line -up front pin to be inline with pin guards or center it in the rear aperture ? I am using the larger rear aperture.
Does it matter which is sighted in first,iron or red dot?
Your input is appreciated!
I always sight in an optic first and then move my buis to co-witness. Then I remove the optic (or turn it off) and check zero with irons.
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I always zero my optic first then cowitness my irons and verify zero, it’s usually a click or two off at most. When zeroing your irons use the smaller aperture, it’s easier to center the front sight. Your sight picture should be similar to the picture below. The ears of the front sight will be different but in generally the same spot. I recommend finding the most comfortable hold and getting a good mental image of how your sights look that way you can be more consistent and get your sight picture faster.
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Center it with the rear
Just to be the oddball (so far) and let you know there are plenty of ways to do it, I always sight in my iron sights first. I get them tweaked in and then mount the optic. I typically have completely fold away irons, so once they are done, it’s full attention to the optic. That way (in my mind at least) the optic is never removed/reattached from the time it is fully zeroed.
If I am truly cowitnessing with a 1x red dot optic, I’ll adjust the dot onto the combined aimpoint of the irons (to get the shots on the middle of the paper) and then fold them out of the way to finish zeroing it in. If I am not fully cowitnessing or if I have a powered optic, I just start zeroing the optic (starting at short range) with the irons down and out of the way.
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Also, I was taught that when you mount your red dot, push it forward against the rail slot as you tighten it down. From what I understand, doing this ensures that you will always have a repeatable position of index (if you remove it), and will prevent it from losing zero due to recoil possibly moving the base back/forth in the rail slot.
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Personally, I dont recommend using the larger rear aperture. It is not as repeatable for a consistent sight picture. It was designed to be used when you had to be further away due to gas masks. While the smaller circle is more of a pain to use, if you want a reliable sight picture, you need to use it.
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All good advice….and I am impressed…I’ve been zeroing & shooting the AR’s for 50 years….and reading everyone’s posts above proves I am never too old to learn. On thing I didn’t see mentioned was the positioning of the rear aperture. A little forward or rear biased will adjust the appearance of the rear aperture so you can precisely align it with the front dog ears……no need to memorize it……the front sight should fit perfectly every time. I have a preference for the “HK” type BUIS because the round front dog ears can be perfectly aligned with the round rear aperture.
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