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Rifle Scopes 50mm vs 56mm

It's a hair brighter at the highest powers but pick the one that is best for your rifle set up. If you can run a 56mm without it being mounted too high then get it but if you need to mount a little lower due to the rifle or your body structure then go with the 50mm.
 
A while back, some dude on here did a test of his 50mm NF vs his 56mm NF in dusk conditions. The 56mm allowed him to see a target something like 2-3minutes longer as darkness fell. I don't remember all the specifics nor was it the most scientific test, but the general conclusion was interesting and enlightening. We are probably NOT taking about a material increase low light performance with the bigger objective, at least that was what I took away.
 
All things being equal I believe the 56mm would give you a more forgiving eyebox.

Course doesn't mean all things are equal and that it was designed to do that.
 
The x56 would be my choice if you can mount it comfortably. If not, then get the x50. The nice thing about the x56 was commented on by hk dave. It is much more forgiving.
 
All things being equal I believe the 56mm would give you a more forgiving eyebox.

True statement.

Exit pupil = Objective diam/magnification

56mm/22 = 2.55mm

50mm/22 = 2.27mm

Bigger is better.

I've also personally witnessed the difference larger obj diameters make on lowlight performance, watching deer in the field, and comparing the last moment a properly aimed shot could be made. Of course, prescription and coatings are a huge factor in this as well, but the 56mm obj will provide allow you to make a shot a minute or two earlier in the morning, or a minute or two later in the evening, as compared to a 50mm.

It will also make the scope a bit brighter at higher magnification.

Bottom line: It really isn't a big difference. I wouldn't shy away from the 50, but if they're both the same price and availabilty, I'd choose the 56.

My 42mm March F is awesome.
 
From what you guys have said I think the 50mm will fit the bill just fine. Spoke with someone through email about this from Mile High Shooting and they said they sold the 50 10-1 against the 56. They have been great with my questions and will be getting my business.
 
I agree with you snax90. Once upon a time I was all about objective size and if you are only punching paper it still might be the way to go. But I hunt and size and weight matters and having an extra 2-3 minutes at dusk is not a concern when I try to be out of the woods by then.
 
I took a Long Range Intro Class and the shooters with the 56mm could see the further targets much farther from my experience. I have a Lupy mk4 4.5-14x50 and at 1200 yards it was really hitting the limit at 14 and going from dusk to dark.

But even at that range, the 56mm crowd were also having difficulty, they can spot the target but in the going from spotting to calculating to take the shot.......the 56mm didn't help anymore.
 
if you use the scope in low-light conditions, the larger the better.

if you use it for hunting - match it with your binos (about 8x56 or similar)
if it's mainly about punching paper during the day, 50 is probably more than fine.
 
I have both a 3.5x15x50 and a 5.5x22x50 mounted on rifles. I looked at the 56 but decided against getting it due to the additional bulk especially for rifles I hunt with. The ability to mount with lower rings outweighed the minimal benefits of having a larger objective.
 
I have the 5.5x22x50 and didn't consider the 56mm. My NF's are dependable and very repeatable. If it all about the glass, I wouldn't buy the NF to start with. I had an IOR that would smoke the NF as far as glass went, but it would not track with the NF. The NF glass is plenty good enough and with the dependable tracking it is the only scope that interests me. But, I would sure like to play with S@B PII.
 
I have 2 8-32X56mm Nightforce scopes. 1 mounted on AIAW the other on a TRG 22. On all my other Nightforce scopes I have 50mm scopes with the exception of 1 1-4X24. I choose the objective with the use of the rifle in mind
 
I bought one of each with the same reticle and compared them at an improvised eye/color chart as darkness fell.
Academically speaking, the 56mm should have been superior but I could not tell any difference. None, not 2-3 minutes, not 2-3 seconds.
I still own some of both but I never buy the 56mm if i can find what I want in a 50mm.

My advice: buy the 56mm if it doesn't affect ring height (AR-15 platforms) and convince yourself that it is better.
On bolt guns, I would avoid high rings, stay with the 50mm and know that I'm not giving anything up.
 
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Well, assuming you have a scope body that takes advantage of the 56mm objective, as long as we are just talking about image quality and not a mounting convenience, then 56 is better. If you need quick acquisition for a running shot, then a lower profile has merit. 50mm may be enough, if you don't hunt the extra ten minutes of dawn and dusk, but then we start rationalizing, (like) I have a 4.5X14 Conquest with a 44mm objective that is very hard to beat. But, I also have a couple 56mm scopes and they are awesome and I appreciate what they are capable of. For me, the mounting height is a distraction. I know what my application is, for the most part and if I need lowlight performance, I know where to look. BB
 
I like my March F as well with its 42mm objective. With proper cheek weld, there is no problem with the exit pupil due to its size restriction. I don't feel under scoped when comparing it to my PH with the 56mm objective. I don't hunt with either in low light conditions though. Get the 50mm. You won't notice the difference.
 
Really? 1/4 mm.difference in exit pupil?
And 2 or 3 minutes more low light shooting?

Sounds very much like hair splitting or the Medieval "discussion" on how many angels could stand on the head of a pin.
50 mm. objective sounds fine. After that go to a night vision add-on if it's that important.
Jus' sayin'...