On my build I'm planning to put a magnified optic cowitnessed to the iron sights, as well as a reflex sight mounted on an picatinny angle mount.. like this: http://www.cheaperthandirt.com/SearchResults.aspx?site=All+Products&num=10&q=Angle+Mount

I'm wondering how difficult it is to zero a reflex sight that is mounted like that.. can anyone guide me through it, what I have to take into consideration that is different from a normal mount?  Also, as a side question, is it possible to zero a rifle within 25 yards (like zeroing it indoors in my house, since I live in a city and don't have easy access to a range because I don't have a car).  I can always do a more precise zero later on (for the scope) when I do go to the range.  But I'm mostly concerned with having that reflex sight zeroed first.  

I'd be using a laser boresighter.

ps, if anyone knows of a place selling an angle mount like that that includes an allen wrench (this one doesn't) please post it

Lots of views.. no replies?

The link

Well your link is just to a search.  When I clicked a YHM angle mount came up.  First of all, I have no idea how/where you are mounting the angled optic. . .I'm guessing off the forearm so you rotate the rifle 45 degrees CCW and shoot with the red dot.

So first, you cannot cowitness a magnified optic IME.  The eyepiece must be where the rear sight would be unless it is an extended eye relief optic.  Still, even at 1x(or close), the front sight still has a certain fish aquarium look to it.  

So I'll assume by cowitness, you mean have the optic at a similar line of sight and detachable.  First, you will need a low profile RR BUIS.  ARMS 40L is what I use.  I think MI, Troy and a few others make lo pro BUIS.  There is still no guarantee it will fit.  That comes from this formula:

SH = OLOS - 1/2(ED) - FOC  where -
 SH = Max sight height
 OLOS = Height of your optical line of sight (rail to centerline of optic)
 ED  =  Eyepiece diameter
 FOC = Factor of calculation i.e. possible error(I use ~.1")

OLOS = RH + SRH
 RH = Riser height from top of rail to top of rail
 SRH = Scope ring height from top of rail to center of line of sight

Now for an optic mount:  You will need a QR riser or 1pc QR mount.  There is a link which ends up in everyone of these posts for all of your 1 pc mount choices.  I went rings + riser.  I used the Larue QR riser + TPS steel rings.

Each sighting system will be sighted in like normal.  The red dot will need the rifle to be sighted in with the rifle located.  Since it won't be located directly above your bore, you need to sight in for a distance like 25 yards and then check your actual POI at 10  and 50 yards.  Trouble with angled sights is that the angle you shoot at can vary widely which will affect your ability to put bullets on top of one another.  

Now, the reason you don't have any replies?  I would guess it is because most readers are thinking "cartoon gun" when they see 3 sighting systems.  YOu would be better to invest in one quality sight system like an Aimpoint, EO Tech, maybe Zoom Dot(jury is still out) or quality magnified optic like a Leupold MRT, S&B short dot, IOR 1 - 6  than buy 2 - 3 inferior sighting products.  I have to ask,  Who will carry this rifle?  Also, gizmos hanging off a rifle hurt it's ability to be deployed.  Make sure the gizmos you hang are being used, or they will piss you off.

BTW, sell the laser boresighter on Ebay.  There is no use for one.  Put your upper in a rest w/o the BCG.  look down the bore and align with the bullseye at 10 - 25 yards.  look through optic and adjust until it is on the bullseye.  Recheck and you're done.  Allen wrenches are available everywhere for like $.50 each.  Don't let that affect your decision.

With no car and living in the city, how/where do you plan on shooting this thing?  Even more reason to buy 1 sight system.