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AR15.COM
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3/8/2008 12:48:01 PM EDT
Basically, how?

I have my AR (Bushmaster XM15 E2S 20" A3 Type) and I have my optics (Nikon Buckmaster 4.5-14x40).

So, what's the best method of mounting them? Is a one piece mount better than rings? How do I figure out the right ring height for this combination? What about BUIS? Does the one piece vs. rings decision affect that choice?

I've looked around, but can't seem to find what I need.

Thanks in advance for your help.
3/8/2008 3:51:35 PM EDT
[#1]
Here is pretty good explanation for you
click me, click me!
3/9/2008 11:27:43 AM EDT
[#2]
Welcome to the jungle of AR magnified optics!

The first question is where you need the scope's eyepiece to get good eye relief with your cheek weld.  If it's above or in front of the charging handle, you'll probably need either a one-piece cantilever mount or medium rings with a rail extender.  A one-piece has the advantage of being sturdy and permanently aligned, but is less flexible.  

Mount the rifle with the shoulder position and cheek weld you'd usually use, and see where the scope needs to be to get good eye relief.  Look at where the eyepiece is relative to the charging handle, and figure out whether you can use rings, or will need something to extend the mounts forward (many people do).

For the height, most people want the scope centerline to be around 1.3-1.5", so they can use the same cheek weld and shoulder position for both iron and optics.

You need to choose the right BUIS and mount height combo to get them to fit.  Since you've got the scope, the trade-off will be between mount height and BUIS height.  Here's how to figure that out.

- Measure the scope eyepiece diameter, with any flip-up caps, and divide that by 2.
- Subtract that from the mount or rings centerline height.
- That gives you the highest BUIS height that will fit under the scope in that mount.

Some ring or mount heights are spec'ed to the centerline, while others are spec'ed to the base of the ring.  For the latter, you need to add 0.5" (for 1" tube) or 0.59" (for 30mm) to get the centerline height.

Here's the Big List of one-piece mounts:

www.maxicon.com/guns/optics/one_piece/ar15_onepiece_mounts.htm


And here are some popular BUIS heights:

ARMS 40 - 0.950" folded (mine is 1.00" even)
Matech - 0.75" folded
ARMS 40L - 0.610" folded
Troy - 0.460" folded
MI MCTAR-SPLP - .4375" folded
YHM-9680 - 0.840" folded (mine is 0.850")


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