Confused about scope mounting heights on AR10/15

[jonyork]

Hi folks,

Hopefully you guy can shed some light on this.

I know that with a traditional rifle you would obtain the “optimal” scope mount height by measuring the objective bell, divide by 2 and get the closest mount height possible.

So a 50mm bell, would be 25mm, therefore a 30mm mount centreline height would be perfect.

But on the flattop/AR world, I find many sources say a 1.5 inch centreline height is best.

What’s the real scoop?

 

[JayCarver]

Yes flattop Ar you want a 1.5" mount for proper eye aliment and cheek weld.

Some like the 1.93" mounts and I have tried them but I prefer the 1.5".

 

[tiriaq]

The scope should be mounted so that your shooting position is comfortable. There is no arbitrary measurement.

 

[jonyork]

The scope should be mounted so that your shooting position is comfortable. There is no arbitrary measurement.

that was my thought as well, and I was taken aback today when I moved my scope with cheapo "medium" mounts on my AR10 since the hunting rifle wasn't going to be doing much for the next few months. To my surprise it was quite uncomfortable and not nice to use, despite it being glued to the rifle and about 1-2mm of space between the objective bell (40mm) and the rails...

Go back to my AR15 with has a Holosun 403A which is lower 1/3, (which I guess is around 1.75 inches?) and it was much more comfortable.

Are cantilevered mounts needed on an AR? I noticed that looking around scopes seem to be all cantilevered and the eyepiece not passing the charging handle. Is that a hard and fast rule?

 

[can14]

Bauer makes a great set of rings for flat tops 1.5" height

 

[rugbydave]

You want 1.5" height. You don't necessarily need a cantilevered mount on an AR-10 for proper eye relief but you will with an AR-15 (unless it's a monolithic upper).

 

[BullOnParade]

I assumed the eyepiece doesn't pass the charging handle to allow access to the charging handle.

 

[old303]

The cantilever lets the scope mount to the rail on top of the receiver, which is important if the rail ends there. A front ring would likely want to sit forward of the receiver.

 

[tiriaq]

Eye relief is a governing factor when scoping an AR. The scope must be positioned so that when the rifle is held in shooting position, the eye is the proper distance from the ocular. Not unusual for a cantilever mount to be needed.

 

[Mystic Precision]

Eye relief will play a big role on what is the best way to mount an optic. For my Athlon, I needed to run a cantilever base as the eye relief will not allow conventional rings to be used.

I have also used spacers as the typical 1.5" height was still too low for me. For me, I much prefer a height closer to 2" tall.

If I can help with a mount, let me know

Jerry

 

[jonyork]

Thanks everyone!

I found a Chinesium mount on amazon that I’m going to try with my cheapo scope to try out the cantilever/height setup so I can test things out for a low price, and once I’m happy I’ll definitely give you a shout Mystic to set me up.

I’ll post some results with my chinesium mount soon for giggles!

 

[Mystic Precision]

Good luck... just keep an eye on the bolts and keep them tight. Some of the alloys used are really soft so the bolts just loosen... and that is not good for consistency.

But you will know what height suits you

Jerry

 

[jonyork]

That’s my intentions as well.

Got an old scope that came combo with a beginner rifle, going to cobble it together to test it out