Mount height for AR15

[JDT]

Just curious what people tend to find is the best mount height for scopes on an AR15? Do people usually opt for standard rings or high / extra?

[DaveT]

It's more an issue of forward canted mounts for eye relief on an AR.

Something like American Defense.

 

 

[DaveT]

Buy the lowest mount version that clears the handguard but you may still find that you need a comb raiser of some sort to  get a decent cheekweld.

[JDT]

I'm looking at the Trijicon Credo 1-8 x 28 which I reckon would get away with standard height. I'd like a canted mount as you said, preferably quick release.

[Bangbangman]

10 hours ago, JDT said:

Just curious what people tend to find is the best mount height for scopes on an AR15? Do people usually opt for standard rings or high / extra?

The answer will depend on the AR. Is it a flat-top? If it is, you may need cantilever mount to get eye relief but also significantly higher than mounts for a “conventional“ rifle or you won’t be able to get your head low enough to see through the scope (ie. the opposite of the usual problem of getting good cheek weld with a trad stock.) 

I have 3 AR flat-top uppers: scope height above bore is typically 2.75”, compared to 1.75” on my “traditional” rifles. No riser required for a snug cheek-weld.

 

I use American Defense (I can’t afford Spuhr) but for the money I was impressed with AR-Stoner mounts.

 

[JDT]

13 hours ago, Bangbangman said:

The answer will depend on the AR. Is it a flat-top? If it is, you may need cantilever mount to get eye relief but also significantly higher than mounts for a “conventional“ rifle or you won’t be able to get your head low enough to see through the scope (ie. the opposite of the usual problem of getting good cheek weld with a trad stock.) 

I have 3 AR flat-top uppers: scope height above bore is typically 2.75”, compared to 1.75” on my “traditional” rifles. No riser required for a snug cheek-weld.

 

I use American Defense (I can’t afford Spuhr) but for the money I was impressed with AR-Stoner mounts.

 

Thanks for the reply. This is just theoretical and me gathering knowledge for now for a future build but yes I do imagine it would be a flat-top. That's just what I was thinking about getting your head low-enough as well, which is one of the reasons I made this post.

I think when I eventually get my build sorted I'll ask the gunsmith if I can come down with my scope and mount and him fit it while I test cheek weld and adjust the stock so I get it set up right first time and should take no longer than an hour. Then I'll know if I need a riser at the time and see if he has any recommendations.

I'd also like a quick-release ideally, but failing that I was thinking a Tier One Monomount. Just had a look at the AD quick-release cantilever mount as well as the Spuhr (certainly pricey as you say!).

Whilst we're on I may as well ask something else - what's the application of different angles on mounts I see (0, 20, 30 MOA etc?). I'm very new to this sort of thing so it's an extra spanner in the works for my decision making haha. Is there a certain mounting angle people prefer for CSR ranges? If someone could give me a brief explanation it would be much appreciated. 

[BamBam]

For quality AR cantilever mount that won't break the bank I'd go with the Warne Skel.

https://www.sportsmanguncentre.co.uk/warne-30mm-msr-gen-2-extended-skeletonized-mount-black-xskel30tw

 

[Bangbangman]

9 hours ago, JDT said:

Thanks for the reply. This is just theoretical and me gathering knowledge for now for a future build but yes I do imagine it would be a flat-top. That's just what I was thinking about getting your head low-enough as well, which is one of the reasons I made this post.

I think when I eventually get my build sorted I'll ask the gunsmith if I can come down with my scope and mount and him fit it while I test cheek weld and adjust the stock so I get it set up right first time and should take no longer than an hour. Then I'll know if I need a riser at the time and see if he has any recommendations.

I'd also like a quick-release ideally, but failing that I was thinking a Tier One Monomount. Just had a look at the AD quick-release cantilever mount as well as the Spuhr (certainly pricey as you say!).

Whilst we're on I may as well ask something else - what's the application of different angles on mounts I see (0, 20, 30 MOA etc?). I'm very new to this sort of thing so it's an extra spanner in the works for my decision making haha. Is there a certain mounting angle people prefer for CSR ranges? If someone could give me a brief explanation it would be much appreciated. 

On a flat-top AR it’s not usually a matter of adjusting stock for correct height- the buffer tube within the stock limits how low you can get your head. While it’s possible to build up the stock or fit a riser if your head is too low, this is not usually the direction you need to go for a flat top.  It’s usually a case of raising the scope by using the right mount. 

 

As for the angled base, a +MOA tilts the front of the scope downward, effectively giving you extra elevation adjustment in your turrets. 

 

This won’t always be necessary but if you know you’ll be shooting long range or using a scope with limited adjustment or a calibre with mortar-like trajectory (458SOCOM, subsonic 300Blk) then it may avoid or reduce problems. I have +20 MOA for mine, as this doesn’t prevent zero’ing at 100yds, doesn’t cause “half-mooning” and still gives that bit of extra elevation.

 

 

[JDT]

Ah right I see, well thanks a lot for taking the time to explain that to me. As this will be for CSR ranges using .223 I'm sure I'd be fine with a standard 0 MOA base then.

I'll also bear in mind what you said about the mount on a flat top. I think what I might have to do in the end is buy 2 of the same model mount that I settle on (one standard, one high) close to the time of build completion so I can test fit both of them and see what works best (could be either as I have quite a small head so may get away with standard...) and then return the one that I don't use within refund period. 

[Roy W]

Sphur do their cantilever mounts in Low, Medium and High. That relates to the height of the scope above the bore.

I went for low to get it as close to the bore as possible. It requires a low head position on the stock, but if you have no neck issues your should be fine.

Unfortunately you won't know until you try