Thanks for the input on my first question re: optic selections.  Got the Unity and EoTechs on hand and started attaching to the AR's..  Trying to figure out what best practice is for placement on the rail.  Have read/watched a lot of articles and videos and seeing various opinions.  

Option A: I put the BUIS on first, then mag, then HWS.  The BUIS is as far back as possible and hangs over the charging handle when folded.  When the mag is folded, it hits the BUIS and partially blocks the HWS.  
1) Is that blocked view normal and just something you learn to live with?
2) Is it normal to shift forward on the stock when using the mag to fit into the eye box?
3) This puts the rear of the HWS almost in line with the rear of the ejection port.

Option B: I put the mag on first, then HWS, then Rear BUIS in front of the HWS....
1) This has the best eye relief position and don't need to slide forward much, if any, when using the magnifier.
2) The mag can fully fold and no longer blocks the view of the HWS.
3) This puts the center of the HWS in line with the rear of the ejection port - is this too far back?
4) This gives me a short sight radius on my BUIS, especially on the 6.75" 300 BO.

This all assumes that I should be trying to put the mag & HWS as close together as possible.

Can someone give me feedback on what is the right/best practice way to set this configuration up?

OPTION A:


OPTION B:


300 BO

Ditch the BUIS or ditch the magnifier. Can’t have both…unless you find an older pair of Kac offset buis:

Attached File


Be prepared to pay a chunk but the ladder is flush and allows the magnifier to fold correctly.

You’ll need offset BUIS for those tall mounts.

Got it.  So when I ditch the BUIS…. Put the magnifier as far back as possible then what about the HWS?  

Better to keep them close, or space out to center over the ejection port?

Put the magnifier where the eye relief works best for you.  For me that usually means rds over the ejection port and magnifier right behind it.

With red dot sights, I always put them as far forward on the receiver as possible.
Just make sure you keep them on the receiver and not the handguard.
Then put the magnifier where ever the eye relief is best for you.

This. Eye relief on magnifiers can be pretty short.

I have one rifle setup with a magnifier and red dot, my rear BUIS is in front of the red dot, but still on the receiver, it’s a 12.65 BCM handguard, so there’s still a decent amount of distance between them.

I’m totally fine with it, I zeroed them at 36 yards and they work just fine.

I wish the magnifier, which does have a QD mount, was a reverse cantilever so the rear BUIS could be in the usual place, but I’m comfortable with them as they are, and prefer it over offset irons.

That's the issue with Unity's riser and FTC magnifier. It deletes the BUIS function. Lots of apologists will say ditch the BUIS or put it in front of your optic, and then you'll have to remove the optic/riser to use the BUIS. This is probably why CAG just runs a Wilcox FTS magnifier mount for the G33 so they can run BUIS.

I tried the Unity stuff and it added almost 4 oz of weight and deleted the rear BUIS. I ditched the Unity stuff and went back to a FTS.

The night vision argument doesn't hold for the FTC magnifier mount because many of the nod users says their tubes hit the magnifier. It seems the FTC magnifier mount is handy for those wearing gas masks.

Thanks for this.  In a lot of the videos I’ve watched, the magnifier and red dot are close together, so that’s why I kept pulling it back on the receiver towards the magnifier.  

I definitely prefer more towards the front, especially when I’m not using the magnifier.

This is exactly where I’m at now.  I need to put the magnifier at the very back end of the rail, otherwise, I end up sliding forward on the stock when using the mag.  

I’ve only tested with dry fire thus far, so may end up adjusting once I get to the range.

The Unity’s are a great product, but would prefer they folded to the side.  

Too much stuff cluttering it up and weighing it down. I'd just go with the optic of choice and position it for best eye relief.  

I prefer my EXPS toward the front of the receiver.

Buis and magnifier end up behind with no spare rail slots.

I run the EoTech STS mount though and don't have any issues.

Here is my AAC 300BLK configuration.
BUIS flush with rear of receiver.
Eotech G45 magnifier.
Eotech EXPS3-2.
I keep everything on the receiver. I'm left handed so the magnifier flips to the left.

Attached File

Actually figuring this out right now as well.  

Not sure about your particular Unity mount but mine has an integral rear BUIS so I was able to dump the stand alone one. Just have the front now.

I run the stock about two notches out. RDS at the front of the upper receiver. I ran into the same problem as you with the magnifier. If I had it directly behind the RDS in that position I would either have to collapse my stock all the way down or crane my head forward when using the magnifier.

I didn’t like having to change up my shooting stance if I were or not using the magnifier. In order to maintain consistency with my stance I elected to run the magnifier all the way to the rear so that I don’t get scope shadow. Again, I was able to do this since I no longer have a stand alone BUIS.

Now I could bring the RDS back and close the distance between it and the magnifier but for right now I’m going to run it all the way forward on the upper receiver. I haven’t found a difference with its position currently or with a shorter gap between it and the mag so I will wait to see and adjust it if I start having any issues or see a benefit.

dumb question.

how is a flip to side and a red dot any better than a lpvo?  seems like a lot of weight and business to get to basically the same place.  

I have a Honosun 510 on the 300blk pistol, 1-4 lpvo no name soon to be a 1-6 Vortex on the 5.56 carbine. I've decided I like the lpvo path.