25mm..30mm

[barrywhite 282]

What advantage has a scope with a 30mm tube over a scope with a 25mm tube .If any at all .With both magnification and lenses the same on the imaginary scopes.

[tegater 789]

Depends what you are using it for, but will genrally let more light through, and sometimes it is required for a greater range of adjustment.

[pestcontrol121 11]

I was told by a very reliable source that some 30mm scopes have the 25mm internals this was done as the 30mm scope was selling better

[tegater 789]

I really dont know. I cant see S & B, IOR, Swarovski etc doing that. Cheaper manufacturer's may do for the reason quoted. It also doesnt explain why some tubes are 34mm and 35mm !!

[HUnter_zero 58]

There is a massive myth in the shooting community that 30mm scopes let more light in. The scopes do not as 25 mm adjustment internal are used. However there is two distinct advantages over a 25mm scope. First, you have a lot more turret adjustment and second you can mount a 30mm scope with a large lens a lot lower due to having a larger diameter tube.

 

I have a 30mm S&B 6x42 and a 25mm S&B 6x42 there is no discernable difference with light gathering. However my 8x56 25mm S&B show slightly better light gathering than either of the 6x42.

 

John

Edited August 19, 2011 by HUnter_zero

[HUnter_zero 58]

explain why some tubes are 34mm and 35mm !!

 

Because most have 60mm objective lenses and having a 25mm tube would mean mounting the scope much too high off the bore.

 

John

[tegater 789]

I think what I really meant, was that they often produce brighter images because the internal lenses are often bigger, which can then transmit the light more effectively. If we compare a S&B 30mm tube against the 34mm tube, then it is quite clearly slightly brighter. But as we agree on the main reason is for a greater adjustment range.

[tegater 789]

The S and B scopes I use both have 50mm objective lenses. This means the centre of the tube, no matter what the size 25, 30 or 34 would be at the same height off the bore. It is the size of the objective lense that determines that, and how high you choose to mount it.

[HUnter_zero 58]

The S and B scopes I use both have 50mm objective lenses. This means the centre of the tube, no matter what the size 25, 30 or 34 would be at the same height off the bore. It is the size of the objective lense that determines that, and how high you choose to mount it.

Okay, now stop and have a good think. Take a good long look at your scopes and you will see that a 30mm tube will enable you to mount the scope lower than a 25mm tube. To put it another way, you can use low mounts on a 30mm tube, if you needed med mounts on a 25mm tube which means you can achieve a better cheek weld with the stock, but of course you will be able to see this with your set ups if you take a gander.

 

John

[HUnter_zero 58]

If we compare a S&B 30mm tube against the 34mm tube, then it is quite clearly slightly brighter.

 

You don't get many "x" x 50 34mm tubed scopes to compare them to your "x" x 50 30mm S&B scope.

 

John

[tegater 789]

My PM11 scope has 34mm tube and my PM1 scope as far as I can tell has 30mm tube. They both have 50mm objective lenses.

I have already said that I dont know if the internal parts are based on 25mm or not. One thing is for certain is that the newer 34mm tube is brighter than the 30mm tube-for whatever reason. I do know that the larger internal lenses will transmit the light more effectively, similar to a larger lens on a camera will generally transmit light better. I am not quite sure what we are discussing here because we both agree on the main reason the tubes are larger. As for 60mm objective lenses, I have never come across these in any scope I have used.

[HUnter_zero 58]

My PM11 scope has 34mm tube and my PM1 scope as far as I can tell has 30mm tube. They both have 50mm objective lenses.

I have already said that I don't know if the internal parts are based on 25mm or not. One thing is for certain is that the newer 34mm tube is brighter than the 30mm tube-for whatever reason.

 

Could be for many reasons including larger internals. The PM11 is a relatively new scope and it's true to say that S&B will have reworked the internals and more over the lenses and lens coatings. As previously discussed, the two main benefits are scope mounting height and as you say internal adjustment parameters with the larger tube having a greater range of adjustment.

It's also true to say that older scopes, such as the Tasco Titan range which came in 30mm format had much higher quality lenses and a very high quality matte finish to all internals which made for a most excellent and crisp image. I'm not sure if it's a real benefit but to my mind the larger diameter tube also gives greater surface area for the mounts to grip but thats just a personal observation and that said, all but one of my S&B scopes have 1" tubes. On the note of S&B scopes. I mounted my NV scope to my .22rf the other night and with ambient street lighting my 6x42 S&B gave a much brighter image than a gen 1+ NV rifle scope, testament to the quality of S&B scopes.

 

My normal set up with a 6x42 S&B

 

Edited August 20, 2011 by HUnter_zero

[tegater 789]

John. I found this an interesting thread because it makes me look at things from a different angle. I have not seen a nv sight on a civilian rifle before, except the new digital ones. What sort of effective range does it have, for identifying foxes for example?

[Alycidon 2]

In my view for 90% of what we do 25mm is sufficient. Sporting shots rarely need more than 3 or 4 minuets of drop, if you do you are to far away !!. Surely scope height in limited by the diameter if the objective bell, mounts can usually be found to get popular scopes objective lenses as low as possible. In my stable my 25mm tube Ziess's comfortably outperform my 30mm tubed Swaro and NSX in ultra low light.

 

A

[HUnter_zero 58]

What sort of effective range does it have, for identifying foxes for example?

 

100 yards or more dependant on the light level ( I use multiple IR sources ). Don't forget it only has three times magnification as well.