Scope Height

[Fissssh]

What is the proper or prime scope height for a AR 15 flat top? Center of scope to center of bore = ?

[problemchild]

What is the proper or prime scope height for a AR 15 flat top? Center of scope to center of bore = ?

I think lower is better or just enough to clear the gun and or sights and also line up with your eye.

[Trapper]

With an AR you will need higher rings, I went with extra high Burris Extreme rings.

http://www.midwayusa.com/viewProduct/?productNumber=810257

[Fissssh]

Why so tall?

With an AR you will need higher rings, I went with extra high Burris Extreme rings.
http://www.midwayusa.com/viewProduct...tNumber=810257

[kazman]

I use ARMS 22 high quick release mount, which is 1.45" rail to center of scope. I needed that to clear the low profile BUIS flip ups ARMS 40L. And I feel higher is better for when I use the charging handle. Also clears the front A2 sight more (even though you won't see it through the scope).

[maxicon]

The general goal is to have the scope centerline at about the same height or a little higher than the iron sight centerline, which is 1.4" above the rail (2.6" above the bore, but height above the rail is what people spec). Note that some rings (like Leupold) are spec'ed to the centerline, while others (like Burris) are spec'ed to the bottom of the ring, and you have to add 0.5" (1") or 0.59" (30mm) to get the centerline height.

On traditional rifles, you want to be as close to the bore as possible, but the AR ergonomics don't work like that. Ideally, you want to use the same shoulder mount and cheek weld whether you're using irons or optics, so you want them to be mounted on the same axis.

3 main concerns when mounting an AR scope:

- Height above the rail, as mentioned above.

- Forward offset. If you shoot anywhere near nose to charging handle, or have a long eyepiece scope, you'll need the scope mounted further forward than just rings on the receiver will allow. How much will depend on your scope, your stock, and your shooting style.

- Clearing the rear BUIS, if you use one. If your BUIS is a tall one, the scope and mount combo may need to be taller to clear the BUIS.

Here's the Big List of AR15 one-piece mounts, including sections on rings and extended rails:

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

Best bets for AR mounts in general (individual preferences will vary, as always):
Under $50 - CAA DVSR, but needs full circle adapter rings with a 1" scope
Under $100 - Burris PEPR - not easy to find in stock right now
Under $150 - GG&G FLT wrench mount, JP Rifles mount
Over $150 - LaRue, ADM, GG&G, Bobro - lots more choices


Here's how to figure out if your scope and mount will clear your BUIS:

- Measure the scope's eyepiece diameter, with flip caps if you're going to use them. Butler Creek usually adds about 0.1" to the diameter. If the scope's going far enough back so the eyepiece isn't over the BUIS, measure the diameter where it is over the BUIS.
- Divide that by 2.
- Subtract that from the centerline height of your mount or rings.
This gives the maximum height BUIS that will fit under that scope/mount combo. Some BUIS have a higher knob or adjustment on the side, and some scopes will clear at the center, but hit off to the side. It's hard to tell if this will be a problem without trying it out.

For example, my Leupold VX1 4-12x40 eyepiece diameter is 1.7" with flip caps - divided by 2 gives 0.85". Mounting it in a 1" LaRue LT-104, which has a 1.41" centerline, would leave (1.41-0.85) = 0.56 as the tallest BUIS that would fit. As you can see from the list below, that leaves out many. This is one reason the Troy BUIS is so popular.

Here are some popular BUIS heights:

ARMS 40 - 0.95" folded (mine is 1.00" even)
YHM-9680 - 0.84" to the top of the windage knob, 0.74" to the top of the sight body
Matech - 0.75" folded at the elevation adjustment, off to the side, 0.6" closer to center
MI ERS - 0.75" folded
GG&G MAD - 0.625" folded
Magpul MBUS - 0.625" folded
ARMS 40L - 0.61" folded (mine is 0.59")
Troy - 0.460" folded
MI MCTAR-SPLP - .438" folded
YHM QDS - 0.435" folded
KAC 300m - 0.315" folded