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  #1  
Old 05-07-2013, 8:32 PM
freedom-lover freedom-lover is offline
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Default 40 mm vs 50 mm Advice

Just completing an AR308 build. I am interested in usage for tactical and also 600 m target shooting. Budget is $500 - $1000, plus another $100 or so for the mount. My initial thought was something along the lines of 4-14x40 (like for example a Leupold Mark 4 with a mil dot reticle, although that model doesn't have external adjustable turrets, which I think I would like).

Last edited by freedom-lover; 05-07-2013 at 8:51 PM..
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  #2  
Old 05-07-2013, 8:43 PM
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If you're planning to shoot when the sun goes down, then the 50mm.
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  #3  
Old 05-07-2013, 10:01 PM
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Yep, the objective size is all about light gathering. The downside is a larger objective diameter and the higher scope mount position needed because of this. In most cases 40mm will be plenty.
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Old 05-08-2013, 1:57 AM
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When it comes to optics, there is always a trade off...

Personally I like larger objective scopes... unless you have a specific application where you want to reduce size and weight (like on a hunting rifle), I generally always opt for the larger objective. Most of my larger optics all sport a 50mm objective.

For optic mounts specific to the AR platform, like the Burris PERP, Larue LT104, or similar mounts generally put your height over bore around 2.7" which will easily accommodate the larger objective size. I also use the same mount for my optics with smaller objectives like a 1-4x scope because it places the optic pretty much where it needs to be.

In your price range, I would look hard at the Vortex Viper PST line. SWFA also came out with a 3-15x42 which would also fit the bill if you opt for a smaller objective size.
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Old 05-08-2013, 7:14 AM
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I just am finishing a build (6.8 AR build)
I am using a 2.5-10x with a 56mm objective lens. I have it in a QD Burris PEPR mount and it sets up perfectly. Same height as my red dots on my other ARs.
that are set up at lower 1/3 co-witness with their BUIS
as a side note,
the Scope is not really co-witness capable (although 2 eyes open is okay at 2.5x, I went ahead and got the Dueck Defense offset Iron sights They are great and cheek weld is the same for both the scope and the sights.
Light pickup is excellent at night with the scope I got. This build is specifically for low-light, early morning, or late evening hunts. Even night hunts, although that is not my norm.

The scope pictured is a Trijicon 2.5-10x 56mm with an illuminated green dot over a mil-dot reticle. No batteries required and the green dot really helps over low light areas or at night.
I paid about $800 for the scope and another $100 for the mount. The Iron sights were $200 in case you are interested in them.





Hope this helps! And good luck!
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  #6  
Old 05-08-2013, 7:36 AM
freedom-lover freedom-lover is offline
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Thanks for the advice. Is a 20 MOA canted scope mount helpful?
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Old 05-08-2013, 9:25 AM
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I think Killer Bee didn't read the part about $500-1000. Far as I know, the only quality scope available with a 35mm tube and 50mm objective is a Vortex Razor coming in at $2K. :P (BTW I don't mean this with any disrespect to Killer Bee, but the internet might make it seem that way. I say this jokingly like a buddy would having beers around a table)

OP, if you're shooting out to 600m, the size of adjustability is unimportant. Just about any decent quality tactical scope will get you to 600m. It's only when you're reaching out to 1000m+ that something like a 35mm tube "might" be needed. I do just fine with a 30mm. :P

If 600 is as far as you'll ever shoot, the 20moa is not required on most scopes... if you however will ever be reaching out past that, the 20moa cant MIGHT be useful depending on your scope.

I too prefer larger objectives whenever possible.
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Old 05-08-2013, 9:43 AM
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I prefer smaller objectives myself.

If you are choosing between good glass at 40mm or acceptable glass at 50, I'll take glass over size.

If that's not an issue, knock yourself out.
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Old 05-08-2013, 9:54 AM
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Quote:
Originally Posted by HK Dave View Post
I think Killer Bee didn't read the part about $500-1000. Far as I know, the only quality scope available with a 35mm tube and 50mm objective is a Vortex Razor coming in at $2K. :P (BTW I don't mean this with any disrespect to Killer Bee, but the internet might make it seem that way. I say this jokingly like a buddy would having beers around a table)

OP, if you're shooting out to 600m, the size of adjustability is unimportant. Just about any decent quality tactical scope will get you to 600m. It's only when you're reaching out to 1000m+ that something like a 35mm tube "might" be needed. I do just fine with a 30mm. :P

If 600 is as far as you'll ever shoot, the 20moa is not required on most scopes... if you however will ever be reaching out past that, the 20moa cant MIGHT be useful depending on your scope.

I too prefer larger objectives whenever possible.


+1 for HKDave. Even with most 1'' scopes with medium magnification range a 20 MOA base usually isnt needed. Some higher magnification scopes with limited internal adjustmnet might need it. If you stick to a 30mm tube that will give you plenty of adjustment in most cases. You mentioned a Mark 4...maybealso take a look at the PST. Vortex has a 4-16X50 PST with a 30mm tube with 75 moa internal adjustment. Plenty out to 600+. Great scope for the money.

Trevor B.
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  #10  
Old 05-08-2013, 11:11 AM
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Quote:
Originally Posted by Whiterabbit View Post
If you are choosing between good glass at 40mm or acceptable glass at 50, I'll take glass over size.
I can agree with that (Quality glass > objective size)... objective size means nothing if the glass is crap...

Chances are a 40mm scope with quality glass with better lens coatings will also be very efficient in light transmission.

All things being equal, not so much.
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Old 05-08-2013, 12:03 PM
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Oh yah, forgot about IOR, great scope... but it certainly isn't with $500-1000.

I think a Vortex Viper would suit the OP well.
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Old 05-08-2013, 12:27 PM
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What are the thoughts on first focal plane reticle vs second focal plane?
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  #13  
Old 05-08-2013, 12:40 PM
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Depends on the style of shooting you do. If you do a lot of holdovers instead of dialing in adjustments, it's well worth it to get FFP.

If you're the type that always shoots at max magnification or always dials in adjustments, then SFP will suit you fine.

Generally speaking, it is more difficult and costly to build an FFP scope over an SFP. So in money terms, you would probably get more bang for the buck getting an SFP with all other things being equal.

With scopes that max out at 10x, I personally don't see a reason for FFP. The reason that is... generally speaking, when shooting in a range where you're using less than 10x, you're not doing large holds. Also when you are shooting a range where you would do holds, then i'd be using the scope maxed to 10x anyhow.

Also the reticle at say... 3x, the hold dots are so tiny, you'd have to be a super eagle man hero of the universe to use them properly.

With scopes over 10x, I will never buy an SFP scope again. All my scopes that magnify beyond 10x are FFP. If I was shooting benchrest or something where all my shots are at 1000 yards... i'd consider an SFP again, but I don't do that type of shooting.
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Old 05-11-2013, 3:55 AM
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Go 40mm. Your eyes can't take advantage of larger light gathering capability over 40mm, just an overkill.
Read this.
http://www.chuckhawks.com/straight_scope.htm
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Old 05-11-2013, 9:53 AM
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Do the math and figure what works best for you for a light gathering lens.

For example a scope set at 8 power with a 56mm Obj will have an exit pupil of 7mm... Or 56mm/8 = 7

42mm/7 = 6 (42mm at 7 mag)

Just divide as follows.... Obj. mm / power = exit pupil.

I used a 42mm and 56mm to show the differences, if you plug in a 50mm you'll see no great advantage over a 42mm.

Now age comes into play as well with what your eyes can really do with this. Youngsters can take advantage of 6mm to 7mm exit pupil while us older folks it starts to diminish down to 5mm. Not an expert, just learning like the rest of us.
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Last edited by zio707; 05-11-2013 at 10:09 AM..
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Old 05-13-2013, 5:37 AM
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Quote:
Originally Posted by ejhc11 View Post
Go 40mm. Your eyes can't take advantage of larger light gathering capability over 40mm, just an overkill.
Read this.
http://www.chuckhawks.com/straight_scope.htm
It is true that depending on your pupil you might not use ALL of the light. However, people that always say smaller is 'enough' never mention that a larger exit pupil will allow for variable head placement. What I mean is your cheek weld can vary and you will still get a full sight picture and not a tunnel effect. Now, in bench shooting, not as important. You're seated and ready to go. However, in hunting, when you need to shoulder at any moment and you might be wearing thicker clothes, etc, having a slightly less critical head placement due to a slightly larger exit pupil is a good thing. Granted, you want to be exact every time, but, you can still be just accurate with a slightly off cheek weld and have a full and bright sight picture with that larger objective.

Trevor B.
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  #17  
Old 05-13-2013, 9:07 AM
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I think I have it narrowed down to the SWFA SS 3-14x42 (30 mm, mil/mil, $699) vs the Vortex Viper HS LR 4-16x44 (30 mm tube, moa/moa, $550).

Any thoughts on which one???
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Old 05-13-2013, 10:25 AM
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Between those two choices, I'd go SWFA personally.

The Vortex Viper HS is a hunting scope and has covered turrets. It's a good scope if you don't plan on making any windage or elevation adjustments on the fly and are good with using the reticle to do holdovers instead.

Given your experience, I'd recommend a used SWFA 3-9x42mm instead. It'll serve you fine and let you get use to the idea of MIL over MOA.
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