25mm..30mm

[HUnter_zero 58]

Surely scope height in limited by the diameter if the objective bell,

 

Okay, it must be the way that I am expressing my self.

 

Take two scopes, one 3-9x56 with a 25mm tube. The other 3-9x56 with a 30mm tube. The 30mm tubed scope can be mounted with lower mounts due to the scope tube being bigger or to put it another way you would need high mounts with the 25mm tube but would only need med mounts with the 30mm tube. The resultant is that you have a better cheek weld with the stock.

 

John

[tegater 789]

Surely scope height in limited by the diameter if the objective bell,

 

Okay, it must be the way that I am expressing my self.

 

Take two scopes, one 3-9x56 with a 25mm tube. The other 3-9x56 with a 30mm tube. The 30mm tubed scope can be mounted with lower mounts due to the scope tube being bigger or to put it another way you would need high mounts with the 25mm tube but would only need med mounts with the 30mm tube. The resultant is that you have a better cheek weld with the stock.

 

John

John.

I still choose to disagree with the above due to the reasons given in comments by myself on post 8 and Alycidon on post 11, I think it is.

If you have a scope, with a 56mm objective, (as in your example), and it is set on the rail, so that the objective lens is for example, at the minimum it can go before it touches the barrel (with whichever size tube) then it doesnt matter, what size the tube is, you will still get the same stockweld, because your eye still looks through the centre of the ocular and objective.

I think you may be getting confused with just using high, med low mounts, out of preferance. Of course, the lower the mount the better the stockweld (generally)

This is one of the reasons, why, I think it is Leupold but I might be wrong, that they have produced a scope with a large diameter objective lens, which has a concave piece at the bottem, because this was the only way to seat it lower to the centre of the bore.

[HUnter_zero 58]



I still choose to disagree with the above

 

Believe me I have no wish to educated for free, however the below diagram is to scale and original. It's a shock that "experienced" marksmen seem to have an issue over this.

 

The mounts are exactly the same, the only difference is the tube diameter, as can be seen using the same height mounts an objective lens increase can be achieved of 10mm by only 2mm clearance towards the bore.

 

The use of the same height mounts would mean that on a 25mm scope the objective bell would be so low it would touch the receiver as can be seen below with both diagrams being of the exact same scale.

 

 

If you have issues understanding that, then so be it.

 

John

Edited August 21, 2011 by HUnter_zero

[tegater 789]

John. Without turning this into a petty argument your diagram is showing you how to get a larger diameter objective by using a smaller tube. One of yours shows a 5mm clerance and one shows a 7 mm clearance. The overall difference being 3mm on your you different objective lens example. This would be reduced if both objective lens were the same diameter and set at the same height. The centre of a tube, is the centre of a tube, it doesn't matter what the diameter is. Now, if you can't get mounts that allow you to mount them the same height, then that is different. John. thanks for the banter, I am learning things here, and I will hold my hands up if I am wrong.

[tegater 789]

John. Having read your above, I can also add, that I dont have "an issue" with the diagram or the concept that you are showing me, it is just not what I am talking about. If you placed two scopes of the same dimensions, other than the tube diameter, on a flat surface, with no mounts, then they would sit identically on that surface, and the centre of each tube, would be identical as well. Quite clearly though, you would need different sized mounts, to set them on the rifle in the same position. The height of the centre of each tube would then still be the same, as to would be your head position. That is all I am saying!

[HUnter_zero 58]

I am learning things here, and I will hold my hands up if I am wrong.

 

Look at both diagrams. In both examples the same height mounts are used in each example but not in each diagram. The first diagram shows that it is possible to mount a larger diameter objective lens when using a 30mm tube, in fact a full 10mm larger objective lens and by doing so you will only raise the sight line by 3mm which is one of the benefits of using a 30mm tube. The second diagram shows that if you were to mount two scopes with the same objective lens diameter using the same height mounting system, the 25mm scope would not clear the action. Now theory would suggest that all you have to do is increase the mount height (trust you have kept up so far) so that the objective lens clears the action - yes? This is where the problems start, because on paper we can set the mounts at any height, in practice we can only obtain preset mount heights and would have to go for the next height mount to enable the 25mm scope to clear the action. In practice the might mean an increased mounting height of 6-12mm (typically 8mm) depending on the manufacture of the mounts, in the above you can see that there is a 3mm difference between the 25mm & 30mm scope centers, the use of the next height mounts would increase the 25mm scope center by 5mm. Finally the use of a 30mm tubed scope means that it is possible to mount the scope lower (see below). It is of course true to say that if you could make any size mounts you needed, custom mount if you like then things would change. It is also true to say that if it were possible to purchase a myriad of mounting systems one would be bound to find lower or higher mounts in one spec or another, but as said typically you can mount a 30mm scope tube lower.

 

 

John

Edited August 21, 2011 by HUnter_zero

[tegater 789]

Ok John. I will concede on this one because we at least agree the issue is one of not being able to do it without custom mounts. As I said, I am not to big to hold my hands up. Thanks for what has been an interesting thread, and I hope to speak again with you on other threads in the future. ATB.