ring/riser/ mount height on AR

**Tim Ault** · March 10th, 2012, 12:28 PM

I've never had a scope on any AR Ive owned but since I have a flat top rec. now I want to try a scope. So if i wanted to mount a scope say a standard 40 mm obj. is there specific rings or do I need a riser or what and what height am i shooting for.

Thanks,Tim

**smit308** · March 10th, 2012, 12:38 PM

I'm sure someone with more knowledge will chime in but, I think a lot of the problem with a scope on an AR is proper eye relief. There specific mounts that cantilever the scope forward to obtain proper relief. I have a LeRue and a Burris, both are QD and both give good sight picture when the rifle is shouldered.

Smit

**fastfive0** · March 13th, 2012, 11:19 AM

The main reason for hi rise mounts on most Ar's is to clear the front sight post. If you have a complete flat top AR with no FSB the get whatever size rings you want, that give you proper sight picture while maintaing your natural points of contact.

**Hawk** · March 13th, 2012, 11:46 AM

Originally Posted by Tim Ault

I've never had a scope on any AR Ive owned but since I have a flat top rec. now I want to try a scope. So if i wanted to mount a scope say a standard 40 mm obj. is there specific rings or do I need a riser or what and what height am i shooting for.

Thanks,Tim

Tim,
The height is not as big of an issue as the eye relief on a AR. To obtain the right eye relief the scope has to be mounted pretty far forward. I have a AR flattop with a Bushnell Elite 4200. I started with mid height Burris rings and a 1/2" cantilevered riser to move the scope mounts past the uppers rail to achieve enough eye relief. I shot this for a few month's but discovered the scope flexed to much for my liking with the 1/2 riser. I did some research and found one of the best and most popular solutions, the Burris P.E.P.R mount. It's a very rigid mount and permits enough adjustment range to satisfy most shooters. I highly recommend it for most uses.

Link:
http://www.midwayusa.com/product/199...op-ar-15-matte

**mythaeus** · March 13th, 2012, 11:46 AM

Originally Posted by fastfive0

The main reason for hi rise mounts on most Ar's is to clear the front sight post. If you have a complete flat top AR with no FSB the get whatever size rings you want, that give you proper sight picture while maintaing your natural points of contact.

Clearing the FSP is not the only reason. The objective lens bell must also clear the rifle. Getting a low/mid/high may not be enough to clear depending on the diameter. Even with the measurements given by Midway in their scope guide can be misleading. I learned this the hard way when ordered a medium and though it would clear my Nikon Prostaff 4-12x40mm. I ended up having to order an "extra high" set (http://www.midwayusa.com/product/810...tte-extra-high), which I used here: http://forum.pafoa.org/gun-pictures-...-best-yet.html (should give you an idea for clearance). I think "high" MAY provide enough clearance, but I was planning on putting a 50mm on this gun so I got extra high.

Al

**Shodan** · March 13th, 2012, 11:54 AM

I'm an AR newb and I went with this on my S&W M&P Sport. You can see the front sight (cowitness) at 1 power but not at 4.

**mythaeus** · March 13th, 2012, 01:32 PM

Originally Posted by Shodan

I'm an AR newb and I went with this on my S&W M&P Sport. You can see the front sight (cowitness) at 1 power but not at 4.

...

Yeah, even at 1x, it's not easy to focus your eye on the front sight with co-witnessing. At magnifications beyond 1x, the minimum focus distance is farther away, well beyond the front sight, that's why you can't see the front sight at all. I put the hex wrench for the my M-223 mount inside my MOE grip (wrapped in plastic so it doesn't move around and rattle) just in case I need to (and have the opportunity to) remove the scope altogether should I need to resort to BUIS.

Al

**Shodan** · March 13th, 2012, 01:48 PM

Originally Posted by mythaeus

Yeah, even at 1x, it's not easy to focus your eye on the front sight with co-witnessing. At magnifications beyond 1x, the minimum focus distance is farther away, well beyond the front sight, that's why you can't see the front sight at all. I put the hex wrench for the my M-223 mount inside my MOE grip (wrapped in plastic so it doesn't move around and rattle) just in case I need to (and have the opportunity to) remove the scope altogether should I need to resort to BUIS.

Al

I'll do the same when I get a grip with an enclosed compartment. I took the AR hunting in Florida and that Nikon 1-4 power seems appropriate for home defense and the very occasional hunting trip (maybe that will change someday). I think they make that mount with quick release levers also.

Regarding co-witnessing - I'm just happy that the front site is not distracting, I don't care so much about the whole co-witness idea.

**mythaeus** · March 13th, 2012, 01:59 PM

Originally Posted by Shodan

I'll do the same when I get a grip with an enclosed compartment. I took the AR hunting in Florida and that Nikon 1-4 power seems appropriate for home defense and the very occasional hunting trip (maybe that will change someday). I think they make that mount with quick release levers also.

Regarding co-witnessing - I'm just happy that the front site is not distracting, I don't care so much about the whole co-witness idea.

Like you, I like the idea of able to shoot at longer distance with 4x and at close range. At 1x, both eyes opened shooting is just fine too. I don't bother with co-witness unless the sight is a red dot, but for some reason I feel the rifle is "naked" with no BUIS. I don't believe I've seen the M223 mount with quick release though. In any case, unlike red dot/holo, unless the glass shattered, there wouldn't be a need to resort to BUIS with one of these M223 1-4x.

Al

**Shodan** · March 13th, 2012, 02:19 PM

I just "heard" that it was, I didn't research it. I think the wrench is "quick release" enough since I won't be staking my life on accessing the BUIS quickly.

I also can shoot it fine with both eyes open on 1 power. The 223 is the first Nikon scope I've owned and I am impressed. I don't know if they are that good or if anything would seem good compared to the other crap I own, lol. But I have since purchased Nikon binos too and love them.