I am new to the AR world and have a slight problem.
I just got a new M&P 15 Sport and bought a Pursuit red dot sight & mini reflex sight from Bass Pro Shop for a little over a $119. My problem is that I don’t see how to mount them without removing the rear sight. Is there some kind of riser I could use to mount the scope to raise it up? I then could mount the red dot on the rail on top of the sight. I think?

Looking on BPS web site it looks like the redot will need a riser.

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Improvise, Adapt, Overcome

I suspect you need a riser. I just use two 1/2" YHM risers (Brownell's) with the similar Bushnell TRS-25 low mount red dot. It's a bit high for co-witness, but works for me.

I've seen riser heights of .86" mentioned as usable.

.83 height riser should give each you an absolute cowitness. Something like this should work fine Leapers UTG 0.83" Medium Profile Riser Mounts for Rifles with Picatinny/Weaver Rail Mounts MNT-RS08L, MNT-RS08S3, MNT-RS08S2. Leapers UTG Riflescope Mounts, Rings & Bases, Leapers UTG Tactical Rails, Leapers Picatinny Rails.

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M&P9/9C/Shieldx2/Sportx2/15-22

Is your problem that you can't physically mount them to the rail or that the rear flip up sight is in the way of mounting the red dot? Typically, you want to mount your red dot as far forward on the receiver rail as you can. Not on the handguard. You'll do this so that you still have a peripheral view while looking through the red dot. It's not a scope. Look at the 15-22 picture thread to get an idea where it should be mounted. If you like it where the rear sight is then that's a personal preference.

If your optic didn't come with a riser to secure it to the top rail then that sucks and not a good value. Return it and get a bushnell trs-25.

If you are trying to mount them both then you are doing it wrong. Pick one or the other unless one offers magnification. In that case, the magnifier wouldn't be a red dot.

I guess this is the red dot? Pursuit X1 Red Dot Scope | Bass Pro Shops

Yes, you'll need a riser for that no matter what.
You're right, the length of nearly 5in crowds the receiver.

Take a look at the Bushnell TR25 or Primary Arms Micro dot.
https://www.primaryarms.com/Primary_Arms_s/586.htm

ChattanoogaPhil, that link you mentioned is right on. The mini reflex sight is just down and to the right on that page.
What I have is “Pursuit X1 prism sight & mini reflex sight combo” that I ordered from Bass Pro.
The catalog showed the red dot mounted on top of the X1 sight. (The X1 has a 3X magnification). I am kinda lost when talking about these ‘cause I think it is a 3X mag. scope and a red dot sight. I haven’t been around the AR platform for very long and lost when trying to find accessories for it. I couldn’t pass up the deal at Bass Pro. I think they were about $120 for both on sale.
Please forgive me if some of these questions are kinda stupid, but I’m learning. (I think)

If you have the 3x prism then you don't need to concern yourself with mounting the rear sight because you can't use your sights with a magnified optic like you can co-witnessing with a 1x red dot optic. Co-witness is just a fancy word for being able to use your sights with a 1x red dot because you can just look straight through the non-magnified glass to use the sights. And no, you can't jack up the prism scope high enough to use your sights underneath. Well I suppose you could, but it would be unusable cheek weld except for a giraffe maybe.

If all this sounds problematic with your optic that's because it is. In addition, that reflex sight sitting on top may not even zero because it's so high. That setup was used on some NCStar scopes and there were guys complaining that it didn't work out. BretVista had the same issues IIRC.

Which one would you recommend that I just use on the M&P 15?
I can use the other one on another firearm.
If it is the red dot, then I can use the iron sights for backup?
I wasn't sure what "co-witness" was about but that makes a lot of sense and I just learned something.
Thanks for your help,
John

Good question.

You mentioned wanting to be able to use your sights. The 3x prism won't allow it so that's out of the question.

The mini reflex has a very small window but with the right riser you might be able to co-witness. Maybe someone here has done it. Something like the below pic. It's been my experience that the mini reflex sights are not really 1x and typically have some magnification. So it might not be the best for co-witness either.

If using your sights is an important criteria then I'd consider returning the entire package and get a Bushnell TRS-25 or Primary Arms MicroDot. Or.... get a riser for the prism sight and forget about using your sights.

The mini reflex are also good for pistols. I've got a Burris FF III on one of my Rugers. Small package goes well on the pistol.