25mm vs 30mm

[KBF]

Been looking at scopes and notice several companies offer scopes say 4.5-14x42. That come in a 25mm and 30mm tubes. What's the advantage of a 30.?

[DaleJ]

Bigger tubes allow brighter image and offer more adjustment vertically and horizontally. The old Leupold VX-3 in 6.5-20 offered about 55 MOA vertical adjustment with its one inch tube. The Sightron 6-24 with 30 mm tube has 120 MOA vertical.

[elkhunter11]

A larger tube allows for more adjustment, but contrary to what some people believe, it does not allow more light transmission.

[DaleJ]

Originally Posted by elkhunter11

A larger tube allows for more adjustment, but contrary to what some people believe, it does not allow more light transmission.

Larger the tube the more light is transmitted. Example: apertures on single lense reflex cameras control or limit light exposure. Example #2, snow goggles, open the hole up to one inch and see how long it takes to go snow blind.

[Pathfinder76]

Originally Posted by DaleJ

Bigger tubes allow brighter image

I thought that myth was debunked years ago.

[Jamie Black R/T]

Originally Posted by elkhunter11

A larger tube allows for more adjustment, but contrary to what some people believe, it does not allow more light transmission.

This ^^

[catnthehat]

Originally Posted by chuck

I thought that myth was debunked years ago.

X2 the exit pupil determines the amount of light trasnmitted from what I understand and have read over the years, but the extra diameter certianly does allow for more vertical adjusment.
Cat

[DaleJ]

What lets more light into a house, large windows or tiny windows?

[catnthehat]

Originally Posted by DaleJ

What lets more light into a house, large windows or tiny windows?

We are n0t talking abut a single pane however, the light goes through a series of magnified panes.
Cat

[catnthehat]

Here's a link that is explained by Ron Spomer
http://www.swarovskioptik.com/huntin...s_but_not_much
Cat

[Lefty-Canuck]

Info taken from an optics website....some stuff to ponder.

30mm scopes were first made in Europe years and years ago for two reasons.

1. Everything was done by hand and a large tube was needed to be able to build the scope.
2. They are on the metric system.

When we started building scopes in the U.S. technology had advanced some and being on the Standard system we built our scopes with 1" tubes.

The German scopes were and are superior because they use better glass, better coatings and better craftsmanship. Most people assume that bigger is better and that must be the reason why German 30mm scopes are brighter. It did not take long for U.S. and Asian scope makers to catch on to this and start offering 30mm scopes. It worked for a while but more and more people are learning the truth with the advent of the Internet. When Leupold first offered a 30mm tube in a hunting scope, they named it the Euro. 30. A competitor dissected one and said, B.S. that scope has 1" guts with a 30mm tube. Leupold's spin doctors quickly changed the name of the new 30mm line of scopes to LR or Long Range and released press releases stating that this new line of scopes has 1" internals with a 30mm tube to allow for more elevation adjustments.

Bottom line is 30mm scopes are 30mm because of the Metric system, they can be brighter than a 1" scope with all other things being equal (# of internal lenses and diameter of objective especially) if the maker takes advantage of the larger internal lenses in a manner that manages the light better (cutting down on distortion and stray light loss). 30mm scopes are also stronger and usually heavier. Biggest advantage is more internal adjustment travel for long range shooting.

LC

[elkhunter11]

I thought that myth was debunked years ago.

Apparently, some people still believe that myth.

[DaleJ]

LC
That's the reason Leupold's 30 mm scopes have such limited internal adjustments. When they finally did get a real 30 mm built it had 150 MOA vertical, that scope was the Mark 4 16 power. That scope is probably the best Leupold ever built.

[Lefty-Canuck]

Originally Posted by DaleJ

LC
That's the reason Leupold's 30 mm scopes have such limited internal adjustments. When they finally did get a real 30 mm built it had 150 MOA vertical, that scope was the Mark 4 16 power. That scope is probably the best Leupold ever built.

So a guy should snap one up if he finds a good used one?

LC

[DaleJ]

Think they still make them.

[jackrabbit000]

Originally Posted by elkhunter11

A larger tube allows for more adjustment, but contrary to what some people believe, it does not allow more light transmission.

This^^^^^^^^^^^^. Larger tube diameter is usual for more adjustment, mainly for added side focus. Does not transmit more light.

[DaleJ]

OK. Reverse the conditions. Take a 3/4" tube scope in a 4 power and observe. The bigger the tube the greater the amount of light can be pass through it.

[elkhunter11]

OK. Reverse the conditions. Take a 3/4" tube scope in a 4 power and observe. The bigger the tube the greater the amount of light can be pass through it.

Obviously you don't understand how light passes through the multiple lenses of a riflescope. If the 3/4" scope is not as bright, it is because the lenses and coatings are of lower quality, or the objective lens is smaller or both.

[Pathfinder76]

I will also add that a 30mm has the advantage of making the scope heavier, bulkier, throwing balance off, and generally not being able to be mounted as low. What's not to like?

[DaleJ]

Originally Posted by chuck

I will also add that a 30mm has the advantage of making the scope heavier, bulkier, throwing balance off, and generally not being able to be mounted as low. What's not to like?

Its more about enough I.D. than O.D. If Nightforce could package their NXS 5.5 - 22X56 in a size similar to the old Leupold VX-3 2.5-8X they would be stupid to produce what they build. The March 8-80X is built on a 34 mm tube and I wish I would of never looked through one because its now a must-have product. Exit pupils greater than 8 mm won't increase brightness, but bigger tubes are sometimes required to maintain the 8 mm exit pupil. Why bigger tubes? More light required would be my guess. If I'm on my gut trying to shoot .5 MOA at 900 meters the least of my worries is having gun balance. I would worry more about my zipper being down when accepting an award, for shooting or BS'ing.

[elkhunter11]

Why bigger tubes? More light required would be my guess.

And like many guesses, it isn't the correct answer.

[gitrdun]

Originally Posted by DaleJ

Its more about enough I.D. than O.D. If Nightforce could package their NXS 5.5 - 22X56 in a size similar to the old Leupold VX-3 2.5-8X they would be stupid to produce what they build. The March 8-80X is built on a 34 mm tube and I wish I would of never looked through one because its now a must-have product. Exit pupils greater than 8 mm won't increase brightness, but bigger tubes are sometimes required to maintain the 8 mm exit pupil. Why bigger tubes? More light required would be my guess. If I'm on my gut trying to shoot .5 MOA at 900 meters the least of my worries is having gun balance. I would worry more about my zipper being down when accepting an award, for shooting or BS'ing.

You do have a way with words......LIKE!

[marxman]

i like 30 mm they are stiffer and the rings hold better. i am pretty sure the light beam is much smaller than either the 30 mm or 1 inch tube and there is no 30 mm advantage there. i like the look after you get used to it. i am not going to claim my 30 mm scopes dont ruin balance and weigh down my rifle i never even gave that a thought so im going to play dumb and live with it

[Jamie Black R/T]

Originally Posted by DaleJ

Its more about enough I.D. than O.D. If Nightforce could package their NXS 5.5 - 22X56 in a size similar to the old Leupold VX-3 2.5-8X they would be stupid to produce what they build. The March 8-80X is built on a 34 mm tube and I wish I would of never looked through one because its now a must-have product. Exit pupils greater than 8 mm won't increase brightness, but bigger tubes are sometimes required to maintain the 8 mm exit pupil. Why bigger tubes? More light required would be my guess. If I'm on my gut trying to shoot .5 MOA at 900 meters the least of my worries is having gun balance. I would worry more about my zipper being down when accepting an award, for shooting or BS'ing.

[wally338]

So ... I guess my 34mm S&B PMII is ultra bright as compared to a 30mm scope

[Metalmike123]

Originally Posted by elkhunter11

A larger tube allows for more adjustment, but contrary to what some people believe, it does not allow more light transmission.

x2. Several representatives from various optic companies (zeiss and bushnell) say the same thing. Just more elevation/windage adjustment.

Some manufacturers utilize different erector tube support systems. Swarovski on the 30mm (possibly all of them still) utilize 4 coil springs as opposed to the single or double leaf spring system. More space required, consequently the use of the 30mm tube. As mentioned earlier the 30mm tube is stiffer then the 1 inch tube.

I would hazard a guess that there are not too many 25mm scope tubes out there. I suspect the number is more like 25.4mm.

Smaller scopes do offer weight and space savings but that in itself is obvious.

[DaleJ]

Originally Posted by wally338

So ... I guess my 34mm S&B PMII is ultra bright as compared to a 30mm scope

Don't think you would have the same performance with smaller tube on the S&B. I have a couple Leupolds in 6.5-20 that Premier Reticle boosted to 12-40. The image with these boosted scopes suffer on heavy overcast days.

[sdeviation]

big ger objective give u a larger image to pass through the lens ,,,and in actuality this image is "reflected light", its not necessarily brighter, but it is more..
and a larger tube allows the scope length to be shorter ,, and this benefit allows for more travel of the erector system..
just look at the length of the 4200`s verses the new 6500`s or even the tacticle lines...long and skinny verses short and fat...