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Shooting & Reloading - Mausers, Big Bores and others >> Big Bore Rifles

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k80
.333 member

Reged: 07/05/04
Posts: 314
Loc: San Antonio ,Texas, U.S.A.

why the small objective
#34879 - 20/07/05 10:16 AM

Why is the small objective scope
usually seen on big bores? I under-
stand that a "large field of view"
is usually not a problem;but why
limit your vision. A 1.5-6X42 I
think would be a big improvement
from a 1.5-5X20. Weight is not a
problem. Is it tradition or just
the look?

--------------------
Ken
San Antonio

Welcome to South Texas

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475Guy
.400 member

Reged: 22/08/03
Posts: 1088
Loc: Kali, US

Re: why the small objective [Re: k80]
#34887 - 20/07/05 01:38 PM

One could be done on low mounts and the other has to done on med or high mounts. With high mounts, your stock and cheek weld would be non-existant and you would crane your neck up so only your jaw would be touching the stock.

Another thing is that to use the lower power scopes is for speed of sight acquisition which is done with both eyes open.

--------------------
Lo do they call to me,
They bid me take my place among
them in the Halls of Valhalla,
Where the brave may live forever.

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DoubleD
.400 member

Reged: 23/11/03
Posts: 2399
Loc: Retired in Oklahoma

Re: why the small objective [Re: 475Guy]
#34888 - 20/07/05 01:44 PM

In reply to:

One could be done on low mounts and the other has to done on med or high mounts. With high mounts, your stock and cheek weld would be non-existant and you would crane your neck up so only your jaw would be touching the stock.

Well, not quite, with a proper cheek piece or comb there is no problem.

Lower power I understand, the smaller objective I don't.

--------------------
DD, Ret.

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HiWall
.275 member

Reged: 01/11/03
Posts: 85
Loc: Brisbane, Qld

Re: why the small objective [Re: DoubleD]
#34897 - 20/07/05 07:29 PM

Light weight scopes in strong mounts are the go. Normally the straight tubes are easier to mount on long actions - eye relief concerns etc. Most of the bigger scopes don't stand up to the recoil of a big bore as well as the smaller ones.

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JPK
.375 member

Reged: 31/08/04
Posts: 734
Loc: Chevy Chase, MD

Re: why the small objective [Re: HiWall]
#34908 - 21/07/05 03:57 AM

The small objective as already pointed out allows low mounting and a decent cheek weld without a comb so high that the rifle can't be used with good express sights too.

For example my 375H&H has a comb height that works pretty well with either the low mounted Luepold 1.5x5 which has a 20mm objective or the express sights. Its not perfect with either though. If the scope were mounted higher I'd need more comb height to avoid loosing the weld. But then the express sights would be useless. The weld definitely reduces perceived recoil.

FYI there is about 3/16" clearence between the comb nose and the bolt. I would not want a monte carlo style stock not only for astetics but also because to me the straight style stock reduces felt recoil.

JPK

Editted: I also recall reading that with relatively low powered scopes such as my Luepold and others that the maximum useable light is transmitted even with very modest objective lenses. I recall that at 4x the 1.5x5 x20mm Luepold with its 20mm objective is transmitting as much light as the eye can use. I believe the source was a buyers guide in the SCI magazine.

Edited by JPK (21/07/05 04:04 AM)

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mikeh416Rigby
.450 member

Reged: 24/02/03
Posts: 6051
Loc: The beautiful Oley Valley, PA....

Re: why the small objective [Re: k80]
#34913 - 21/07/05 08:52 AM

There is also an issue having to deal with mass-weight-inertia. A large, heavier objective bell is more succeptable to breaking off under the recoil generated by a big bore. A gun builder friend of mine had 2 consecutive large objective, expensive European scopes have the objective bell snap off while sighting in his 416 Remington. The scopes were covered by warranty, but that does little good when Mbogo is bearing down on you and your scope is in two pieces.

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Mike_McGuire
.333 member

Reged: 11/06/05
Posts: 348
Loc: Sydney Australia

Re: why the small objective [Re: k80]
#34918 - 21/07/05 10:54 AM

Ken

As has been mentioned the small objective on a low power scope already lets all the light through the eye can use, especially in day time when your pupil is smaller.

The field of view is not determined by the size of the objective.

So in short, from an "optics" point of view of scope used in the day time there is no gain having the bigger objective on a low powered scope.

If you divide the objective size (in mm) by the power the answer you get is the size of the exit pupil and 7mm is the max the eye can use and that is the max your pupil will dilate if you were in the dark. This is why for night use you have the various European scopes that are 8 power and 56 mm objective, the various 8 X 56s.

If you look through a scope and move your head back the "hole" you are looking through will get smaller as you move your head further back until you finally reach a point where the hole does not get any smaller. The small hole you are looking through is now equal to the exil pupil diameter. Thus if you had an 8 X 56 and 8 X 28 scope the hole you would be looking through on the 8 X 56 would be twice the diameter of an 8 X 28 scope. But a 4 X 28 would have the same size hole as a 8 X 56. If you were shooting at night time such as spotlight shooting the image with a 4 X 28 and 8 X 56 would be of equal brightness but of course the image with the 8 X 56 would be twice as big.

Mike

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DUGABOY1
.400 member

Reged: 02/02/03
Posts: 1340
Loc: TEXAS USA

Re: why the small objective [Re: DoubleD]
#34935 - 22/07/05 05:33 AM

In reply to:

One could be done on low mounts and the other has to done on med or high mounts. With high mounts, your stock and cheek weld would be non-existant and you would crane your neck up so only your jaw would be touching the stock.

In reply to:

Well, not quite, with a proper cheek piece or comb there is no problem.

Lower power I understand, the smaller objective I don't.

DoubleD Most rifles that are made as DGRs, have both Iron sights, and scope in QD mounts. A stock, properly set up for a 40MM objective scope will not allow one to use normal Iron sights, when the scope is removed. If the stock is set up for Irons, then the best scope for it is a 20MM objective, and a long eye relief scope, that is well made, and in low rings, and QDs for quick removal. The stock that is set up for the irons, is the best stock for a DGR, and if a scope is to be used, the 20mm is the best choice!

--------------------
..........Mac >>>===(x)===>
DUGABOY1, and MacD37 founding member of DRSS www.doublerifleshooterssociety.com
"If I die today, I have had a life well spent, for I've been to see the Elephant, and smelled the smoke of Africa!"

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atkinson6
.375 member

Reged: 26/01/04
Posts: 678
Loc: Idaho

Re: why the small objective [Re: DUGABOY1]
#35229 - 30/07/05 09:18 AM

A subject that I have expounded on for years, The 20 MM objective will not be knocked off zero as very little protrudes from the front ring and on a DGR, you really don't want, need, more that 3X max...

How often I see "hunters" show up in africa with a 458 Lott and a 4x12 or bigger on it, and invaribly it is out of zero almost daily, or the recoil and rough treatment that goes with Safari life trashes it and they end up using our iron sighted camp gun, and go home elated at how well they shot the irons

...

Next time you go to the range with a big objective scope, sight it in then wack it hard on that big objective and shoot another group....bingo,your knowledge just soared.

All my guns have 3X Leupolds, 1x4 Leupolds, and 1.5x5 Leupolds except one .338 Win and one 300 H&H, they have 2x7 Leupolds....

Bottom line is that for dangerous game, I'll even suggest big game in general, there will never be an instance wherein 3X or 4X will not work for you other than in your mind..

For most big dangerous animals you have a 3 ft. bullseye , besides all you need to do is put the X on the animal and pull the trigger, you don't need to count the ticks on him...I can shoot a deer at 400 yards or further with a 2X scope as well as with a 12X, probably better, I don't have to contend with heat waves and 12 times more wiggle!

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mikeh416Rigby
.450 member

Reged: 24/02/03
Posts: 6051
Loc: The beautiful Oley Valley, PA....

Re: why the small objective [Re: atkinson6]
#35281 - 01/08/05 09:04 AM

I have 4 DG rifles, and the highest magnification on any of them is 1.75 X 6 X 32. My other rifles all wear 2 X 8 X 32, and my varmit rig sports a 4 X 12. When I'm in the field, all my scopes, except the varmit rig, are carried on the lowest setting, and rarely does it get moved from there.

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