Eye Relief Distances on an AR-15/AR-10?

[dfsutton]

All,

I am researching scopes that would be mounted on an AR-15 or possibly an AR-10 variant. I currently have an Aimpoint T-1 on the AR-15, but would like to look at a 1-4x or 1-6x as a more general purpose optic. It might end up on either gun. It would be my first scope purchase, and I do not have much background.

My question, is what eye relief would be viewed as the minimum, maximum, and ideal for a scope to be mounted on either of these rifles.

Also, what is the general consensus on acceptable levels of variance in eye relief from 1x to 4x/6x? For example, how much of a problem is it to have a 4.5" eye relief on 1x and only 3.5" on 6x?

I apologize if these are dumb questions, but at this point I know very little about the subject.

Thanks.

[dfsutton]

ANy input would be much appreciated.

[Crow Hunter]

It depends more on you than anything else. I don't know that there is an ideal.

On my TR24 I have it pretty much centered in the mount with the front edge of the mount even with the front edge of the receiver. I usually shoot with the stock in 1 to 2 notches, depending on what I am wearing. It took me quite a bit of playing around with positions and scope locations on the rail until I got it to where I have 100% field of view in most situations.

If you are a nose to charging handle shooter you can deal with less eye relief. If you are a stock fully extended shooter, you need more eye relief.

In either case, if you get a good Larue mount and a high quality scope that doesn't vary alot between zoom positions, you can and should adjust it until it fits you.

To make a long story short. There isn't an ideal eye relief. However the less it varies between zooms (and they all vary some) the easier it will be to get it setup right for you.

[JSantoro]

The distances noted in user manuals and spec sheets are basically just starting points, because each eye is different; the published stuff is merely the answer to an equation the lab-coat guys hammered out. Only the shooter can truly decide what it needs to be, and that's for them.

As for the final question, if you have a stock with an adjustable LOP, you have any eye relief between 1x-6x covered. I think that an entire inch between the two is out of the ordinary, however. It's usually less, more like .5"-.75" difference.

[dfsutton]

The distances noted in user manuals and spec sheets are basically just starting points, because each eye is different; the published stuff is merely the answer to an equation the lab-coat guys hammered out. Only the shooter can truly decide what it needs to be, and that's for them.

As for the final question, if you have a stock with an adjustable LOP, you have any eye relief between 1x-6x covered. I think that an entire inch between the two is out of the ordinary, however. It's usually less, more like .5"-.75" difference.

How much much of a problem will that 1" difference be from a functional standpoint? I understand each person is different, but I imagine having to change your cheekweld as you switch magnifications could be an issue.

[JSantoro]

Presuming a fixed LOP, I personally think that that's too much.

Becomes a question as to whether or not playing Tipppy the Turtle and craning your neck back and forth to cover that distance as you shift is possible without undue strain and can be done so that you get the best possible field of view out of the optic. Can't really be defined.

Do you have reason to believe that that will be the amount you have to deal with for particular optic(s), or are you just tossing out numbers?

[dfsutton]

Presuming a fixed LOP, I personally think that that's too much.

Becomes a question as to whether or not playing Tipppy the Turtle and craning your neck back and forth to cover that distance as you shift is possible without undue strain and can be done so that you get the best possible field of view out of the optic. Can't really be defined.

Do you have reason to believe that that will be the amount you have to deal with for particular optic(s), or are you just tossing out numbers?

Really, I'm trying to understand the compromises that are made on each scope that is out there.

The reality is that I will be buying a scope that is around $1200 - $1500 and I understand that there will be some sacrifices at that level. I'm trying to see what can be sacrificed and what can't.

I was looking at the Ellis Mk-7 Omega (theoretical or not?) and noticed there was a 1" difference between the 1x and 6x and that's what led to my questions.

[JSantoro]

Think you're probably good in regard to eye relief with that one. The folks I've pinged about it say that the number offered there are a potential range, and that the actual distance tends to be w/in .5", fore and aft. Not bad at all, if true. One guy in particular that actually measured his said he was consistently at 3.75"-4.25".

Good 35mm tubes are unusual, but not horribly so. ADM certainly makes them.

Gig you'd likely see with that optic is POI shift between min and max magnification and washout of the whole reticle in certain lighting conditions; think morning and evening nautical twilight.

Aside: Have you hit the stickied threads at the top of the subforum, yet? The top two in particular may be of use to you.