Hello everybody,
I bought my first AR-15 M&P Sport II. I bought it at Point Blank gun shop and told the guy I would like to buy a red dot sight that would go well with this gun. He gave me the Sight Mark -SM26008 reflex sight. SWEET! I got home and put it on blah blah and shoot it to find its not lined up...Obviously. So I make all the adjustments I can to find that if I want to shoot what I'm pointing at with the red dot, my red dot is actually at the base of the front sight. Not at the tip. If I put the dot on the tip of the front sight, it shoot about 10 inches low but with good grouping. SO, I lowed the red dot and it was fine but now I cant see my target. Again, I'm new to this and I figure the community here could help me more than Youtube is helping me. So, with that said. Should I go with a riser mount? Different red dot sight? Can I simply just lower the front sight? Thank you all very much.

First WELCOME and Congrats on your new Sport, I just got mine last week and will be putting a Red Dot on it so this is a good thread for me.. Sorry no help but Il sure Lowegan and others will chime in with GREAT advice

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9mm Shield

In order to have the iron sights and the red dot co-witness, the appropriate riser must be used. I fear that yours is a quarter inch or so too short. Most sight manufacturers will specify what riser is needed for mil spec iron sight co-witness.

Thanks cahotshoe,
I will have to look around on the box or their website to see what it says about a riser mount size. I'll post with what I find.

So, I didn't find any information about the riser mount so I did some research and I may end up going with the lower 1/3 co-witness and I read somebody saying use a 1 inch riser mount. I sure hope this helps.

Should suit you just fine. I use this UTG mount with my PA Micro-dot. It's 0.83" and provides absolute co-witness with the FSP and my mbus, which I prefer. The 1" will work too, it will just sit a little higher.

Not necessarily... depends on the build of the optic.

OP, you will want the center of your optic to be 1.4" above the rail on the receiver for absolute co-witness, and a little higher for lower 1/3rd. So mount your optic to the rail, measure the distance from center to the top of the rail, subtract it from 1.4" and that will tell you how high you need to raise it for absolute co-witness.

I have the same set up on my sport II and I don't use a riser. In order to get your sight close you must use both the front and rear sights.
Zero your rifle with the irons then put on the Sightmark. Now that you are close to zero, use the red dot, easier to work with, and with both sights, put the dot on the top of the front post still using the front and the rear sight. Once you have done that, your sight should be close enough that minor adjustments will get zero.

Forget about using any additional riser with that sight. The housing is the riser and is designed to cowitness as is. Even the lowest rail riser will put the optic way too high. Take that thing back and get a PA MicroDot or Bushnell TRS-25 then you can select absolute or lower 1/3 cowitness riser.


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