Scope height ?

The #1 community for Gun Owners in Indiana

Member Benefits:

  • Fewer Ads!
  • Discuss all aspects of firearm ownership
  • Discuss anti-gun legislation
  • Buy, sell, and trade in the classified section
  • Chat with Local gun shops, ranges, trainers & other businesses
  • Discover free outdoor shooting areas
  • View up to date on firearm-related events
  • Share photos & video with other members
  • ...and so much more!
  • 24Carat

    Master
    Rating - 100%
    1   0   0
    Aug 20, 2010
    2,897
    63
    Newburgh
    As close to the bore centerline as possible is the rule of thumb, but:


    I just picked up a Bushmaster XM-15 E2S 20" A3M4 at what I thought was a decent Black Friday price of $699.00. My first AR platform.


    Being as it is an A3/A4 as in a flat top with a removable carry handle and an original M16 type front sight/gas block, I am thinking a set of high rings will get my scope line of sight above the front sight post?

    Thoughts? Pics?
     

    Stschil

    Grandmaster
    Rating - 0%
    0   0   0
    Aug 24, 2010
    5,995
    63
    At the edge of sanit
    I've shot several of other peoples' AR's who've used high mounts and/or co-witness rings to raise the scope sight line above the fixed front irons and have found it difficult to maintain a solid cheek weld. Conversely, I've handled ARs that have standard rings and fixed front sights and have found that the post isn't really a distraction and I can still get a good, repeatable sight picture though the optics.
    My suggestion would be to mount your scope with standard rings first and see how it goes.
     

    42769vette

    Grandmaster
    Industry Partner
    Rating - 100%
    52   0   0
    Oct 6, 2008
    15,222
    113
    south of richmond in
    You wont get your scope above the front sight post, but your will zoom through it. Rule of thumb is the front sight disappears around 2.5-3x of zoom.

    Most shooters can not get away with high rings. A lot is going to depend on the scope your using's eye relief, but your probably going to need a cantilever mount. The rule of thumb is to mount bolt action's as close to the barrel as possible, but that does not hold true on the AR platform. If you sholder your rifle you will notice your head naturally rides higher than it does on a bolt gun, therefor your scope has to ride higher as well.
     

    Stschil

    Grandmaster
    Rating - 0%
    0   0   0
    Aug 24, 2010
    5,995
    63
    At the edge of sanit
    Disregard my previous post. For some reason, I was thinking 'with the carry handle'. After re-reading, I went and dug my Rock River out of the safe. Sure enough, I have a 1" riser under the standard rings. This rifle is dead nuts accurate and I have never had issues with either eye relief or sold cheek weld with this set up.
    image.jpg image.jpg
     

    Nate Suns

    Marksman
    Rating - 100%
    9   0   0
    Jan 15, 2013
    211
    18
    Fishers
    Disregard my previous post. For some reason, I was thinking 'with the carry handle'. After re-reading, I went and dug my Rock River out of the safe. Sure enough, I have a 1" riser under the standard rings. This rifle is dead nuts accurate and I have never had issues with either eye relief or sold cheek weld with this set up.
    View attachment 33689 View attachment 33690

    Which riser are you using on that rifle. I'm looking for one for when I feel like moving my scope over to my AR for plinking around. Do you ever have problems with it becoming loose?
     
    Last edited:

    Stschil

    Grandmaster
    Rating - 0%
    0   0   0
    Aug 24, 2010
    5,995
    63
    At the edge of sanit
    Honestly, I don't know the manufacturer. My wife bought the scope and had it mounted at Gander. It has knurled thumb screws on the one side and the threads have loctite on them. It's stayed solid for several years so far.
     

    42769vette

    Grandmaster
    Industry Partner
    Rating - 100%
    52   0   0
    Oct 6, 2008
    15,222
    113
    south of richmond in
    Can someone explain to me why you would want to use a riser and rings making a extra week point over the industry standard cantilever mount? It's a pratice I've never understood.

    Also if you use proper shooting forum and extend your neck a riser and rings does not allow for a scope with over 2 inchs of eye relief.

    There is a reason almost no one who is serious about AR shooting uses 2 pieces to get the mount close to being right when 1 piece gets it 100% right.
     

    ol' Huff

    Sharpshooter
    Rating - 100%
    1   0   0
    Mar 8, 2012
    567
    28
    42769Vette is spot on in this regard. A shadow of the tower may appear at 3x but by 4x it's gone. It's simply not an issue if the proper cantilever mount is used.
     

    cwillour

    Expert
    Rating - 100%
    90   0   0
    Dec 10, 2011
    1,144
    38
    Northern Indiana
    Can someone explain to me why you would want to use a riser and rings making a extra week point over the industry standard cantilever mount? It's a pratice I've never understood.

    Depends on the level of accuracy you expect to achieve with your AR. If you pick up one niece piece of glass and want to be able to move if between a hunting-accurate AR (i.e. need not be <1 MOA) and a bolt gun, I am not aware of a better method than using decent QR rings (Warne) on the scope at the correct height for the bolt gun and a cantilever riser on the AR.

    img_0106.jpg


    While this was a temporary solution, I didn't have any issues with the mount for my purposes and got pretty consistent <0.75 MOA groups with the $0.40/rd 50gr Fiocchi V-Max. Not to say it wouldn't have been an issue if I was trying to tune a load for <0.5 MOA groups, but the groups were plenty good for my needs. :dunno:
     
    Last edited:

    gregkl

    Outlier
    Site Supporter
    Rating - 100%
    33   0   0
    Apr 8, 2012
    11,868
    77
    Bloomington
    You wont get your scope above the front sight post, but your will zoom through it. Rule of thumb is the front sight disappears around 2.5-3x of zoom.

    Most shooters can not get away with high rings. A lot is going to depend on the scope your using's eye relief, but your probably going to need a cantilever mount. The rule of thumb is to mount bolt action's as close to the barrel as possible, but that does not hold true on the AR platform. If you sholder your rifle you will notice your head naturally rides higher than it does on a bolt gun, therefor your scope has to ride higher as well.

    If you remove the front post but leave the rest of the front sight on, will it cause issues at 1X like on a 1-4X scope?
     

    Stang51d

    Expert
    Rating - 100%
    2   0   0
    Apr 25, 2012
    766
    28
    Centerpoint
    Being right handed and left eye dominant, I either have to jack up the scope so I can get my left eye to it, or shoot left handed. Going left handed will work but right handed with a high scope is much easier.
     

    gregkl

    Outlier
    Site Supporter
    Rating - 100%
    33   0   0
    Apr 8, 2012
    11,868
    77
    Bloomington
    Being right handed and left eye dominant, I either have to jack up the scope so I can get my left eye to it, or shoot left handed. Going left handed will work but right handed with a high scope is much easier.

    I'm the same as you; cross dominant. I just shoot with either the left eye closed or put a piece of opaque cellophane tape on the left lens of my shooting glasses like I do for Trap.
     

    24Carat

    Master
    Rating - 100%
    1   0   0
    Aug 20, 2010
    2,897
    63
    Newburgh
    You wont get your scope above the front sight post, but your will zoom through it. Rule of thumb is the front sight disappears around 2.5-3x of zoom.

    On another forum I got a response saying that because of the focal plane on my 50mm objective scope my sight picture wouldn't be affected behind the front sight.
     

    42769vette

    Grandmaster
    Industry Partner
    Rating - 100%
    52   0   0
    Oct 6, 2008
    15,222
    113
    south of richmond in
    Depends on the level of accuracy you expect to achieve with your AR. If you pick up one niece piece of glass and want to be able to move if between a hunting-accurate AR (i.e. need not be <1 MOA) and a bolt gun, I am not aware of a better method than using decent QR rings (Warne) on the scope at the correct height for the bolt gun and a cantilever riser on the AR.

    img_0106.jpg


    While this was a temporary solution, I didn't have any issues with the mount for my purposes and got pretty consistent <0.75 MOA groups with the $0.40/rd 50gr Fiocchi V-Max. Not to say it wouldn't have been an issue if I was trying to tune a load for <0.5 MOA groups, but the groups were plenty good for my needs. :dunno:


    That base has a extension making it possible but sill not a great idea. I'm on my phone so I can't post links, but look up the American defense SL. It's about .2 low for a AR, and .1 high on most bolt actions (bolt actions have more variance on those numbers that AR's), it returns to zero better, and is 1 piece working as 1 piece not 2 pieces working in conjunction. In a couple months there will be a even better option but it's sill in the design phases with a very reputable company.

    All this is off topic as we are talking about AR'S but it's good food for thought.
     

    42769vette

    Grandmaster
    Industry Partner
    Rating - 100%
    52   0   0
    Oct 6, 2008
    15,222
    113
    south of richmond in
    If you remove the front post but leave the rest of the front sight on, will it cause issues at 1X like on a 1-4X scope?



    If you leave the front post on it won't cause issues. You will be able to see it but it's no where near a issue (similar to cowitnessing but it won't work as a cowitness). If you like you can hacksaw a front post off above the gas tube and it works as a ugly but effective remedy.
     

    cwillour

    Expert
    Rating - 100%
    90   0   0
    Dec 10, 2011
    1,144
    38
    Northern Indiana
    That base has a extension making it possible but sill not a great idea. I'm on my phone so I can't post links, but look up the American defense SL. It's about .2 low for a AR, and .1 high on most bolt actions (bolt actions have more variance on those numbers that AR's), it returns to zero better, and is 1 piece working as 1 piece not 2 pieces working in conjunction. In a couple months there will be a even better option but it's sill in the design phases with a very reputable company.

    All this is off topic as we are talking about AR'S but it's good food for thought.


    Vette: Downside with the ADM SL is no cantilever, which makes it a no-go for me. The S can be had with a little cantilever, but it pushes the scope up another 0.2 for the bolt.

    24C: With the one-piece mounts, my scopes seem to sit with the crosshairs just above the FSP. I can still see the post at low magnification, bit it has never really bothered me. Unless you have a compelling reason (IYO) to use a cantilever riser, I would go the one piece route.

    Depending on the scope and your head positioning, you may find the Burris PEPR mount to be a little short on eye relief. I didn't have a problem with the 1.5-5x Mark 4, but I would need more cantilever for the Weaver 1-5x Dangerous Game.
     

    42769vette

    Grandmaster
    Industry Partner
    Rating - 100%
    52   0   0
    Oct 6, 2008
    15,222
    113
    south of richmond in
    Downside with the ADM SL is no cantilever, which makes it a no-go for me. The S can be had with a little cantilever, but it pushes the scope up another 0.2 for the bolt.

    Form the OP, most of my scopes seem to sit with the crosshairs just above the FSP. I can still see the post at low magnification, bit it has never really bothered me. Unless you have a compelling reason (IYO) to use a cantilever riser, I would go the one piece route.

    Depending on the scope and your head positioning, you may find the Burris PEPR mount to be a little short on eye relief. I didn't have a problem with the 1.5-5x Mark 4, but I would need more cantilever for the Weaver 1-5x Dangerous Game.


    It has no cantilever, but as long as the front recoil lug is on the rail your GTG. With that being the case you get about 1 inch of offset by hanging the front of the base off the front of the reciever.
     
    Top Bottom