30mm vs. 1 Inch scope tubes?

[One Day...]

Twilight Factor (???)

I do not know the origin of the "twilight factor" measurement. It is said to be a measure of how much detail can be seen in low light. The formula to calculate it is: square root of magnification x objective diameter in mm. For example the great Swarovski Z8 1.7-13.3 x 42 scope has a "twilight factor" of 23.63 at 13.3x (√ 13.3 x 42), 15.87 at 6x (√ 6 x 42) and 8.44 at 1.5x (√ 1.5 x 42).

I fully understand that magnification is needed to see details, but I personally do not think that twilight factor is a really useful measure. For example in the above example for the exceptional Z8 1.7-13.3 x 42 scope, the "twilight factor" leads you to expect that you will see more detail at dusk and dawn with the scope set on 13.3x ("twilight factor" of ~24) than you will if you set it at 6x ("twilight factor" of ~16).

​

If you do this, the amount of light that reaches your 7 mm fully dilated pupil at dusk or dawn with the scope set at 13.3x will be a 3.15 mm exit pupil light beam (42 mm objective / 13.3 magnification = 3.15 mm exit pupil light beam). My personal experience is that with such a narrow exit pupil light beam, I personally could not care what magnification is involved because the light beam does not bring to my eye even half of the light it needs to see anything other than a black blob that could be, to use CoElkHunter's earlier very good example, a bush (?), a cow (?), or a 6x6 elk (?) ...

I personally think that it is much more realistic to establish the fact that you want a 7 mm exit pupil light beam at dusk and dawn and a 3 mm exit pupil light beam in full daylight, and that if you need more magnification, you simply need a larger objective, period. For examples:

If 6x magnification with a 42 mm objective is not enough at dusk and dawn, which I totally agree with to see fine details (e.g. elk tines), then 8x magnification with 56 mm will certainly provide more details because it provides additional magnification while still providing a 7 mm beam.​

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Similarly, if 10x magnification with a 40 mm objective is not enough in full daylight, which I totally agree with to see very fine details (e.g. mountain goat trophy characteristics), then 20x magnification with a 80 mm objective will certainly provide more details because it provides twice the magnification while still providing a 4 mm beam.​

In the end, this is why really powerful magnification binoculars (and scopes) MUST have huge objectives...

For example... when guiding chamois hunters in France once upon a time, I used to carry Steiner 20 x 80 binocs. Very unwieldy maybe, but they provided BOTH enough magnification (20x) and enough light in full day light (4 mm exit pupil light beam) to identify a grand old Class III Chamois trophy (Hint: the penalty for killing erroneously a Class II adult Chamois when in possession of a coveted Class III tag was forfeiting of trophy, heavy 4 figure $x,xxx fine, and 3 year suspension of hunting license... Ouch if as a guide you say "shoot"...). These mammoth Steiner 20 x 80 binocs worked very well during the day but they were useless at dusk or dawn. I therefore ALSO carried in the backpack a pair of Zeiss 8x56 BGA...

In full daylight the 20x "very good" glass Steiner showed things that the 8x "exceptional" glass Zeiss simply could not show, even though the quality of the Zeiss glass far exceeded the quality of the Steiner glass. But even though the Steiner 20 x 80 had a twilight factor of 40 (√ 20 x 80), which was twice that of the Zeiss 8 x 56 twilight factor of 21 (√ 8 x 56), I guarantee you that the 7 mm exit pupil light beam of the 8 x 56 made them great at dawn and dusk, while the 4 mm exit pupil light beam of the Steiner made them all but unusable at dawn and dusk...

The only way to glass comfortably for hours, hunting Class III grand old Chamois in the French Alps with mammoth 20 x 80 binocs...

Relative Brightness (???)

Another concept that floated at a time was "relative brightness" to measure how bright a scope or binoculars image is. Same story, I do not know what is the origin of "relative brightness" but the formula for it is to square the exit pupil. So, to continue the same example as above, the Steiner 20 x 80 have a "relative brightness" of 16 (80 / 20 = 4 then 4 x 4 = 16) and the Zeiss 8 x 56 have a "relative brightness" of 49 (56 / 8 = 7 then 7 x 7 = 49). I personally never grasped what comparing a "relative brightness" of 16 to 49 would indicate that comparing an exit pupil (i.e. light beam diameter) of 4 to 7 would not convey...

This is likely a bit too long of a post (again!) but these are difficult concepts to explain in 3 sentences. I hope this was of interest

 

[mark-hunter]

I have 1” scopes on all of my rifles for the hunting I’ve done in North America forever. I’ve read here a lot where 30mm tubes are recommended? Are they worth the extra weight and/or better for lower powered scopes? I’m asking because I have a .375 and .416 I’m wanting to put scopes on. Thanks!

I skipped number of previous posts, and will jump on basic question.

Larger diameter scope tube, gives wider range of internal adjustments.

This means with wider scope tube you will have more clicks for additional elevation.
So, more clicks means - going to longer range with same caliber rifle.

For additional range, on the same caliber rifle, next step would be to put mounts or piccatiny rail with inclination, of 20 or 25 MOA. The range of rifle can effectively be increased in this way as long as bullet is supersonic.

For even more range, then ever wider scope tube plus larger caliber rifle.
etc

For hunting purposes, old fashion hunting that is - 200 meters or a bit longer, 1 inch scope tube will be sufficient. I dont think anybody uses 416 as long range rifle, DG is close call.

So, one inch scope tube is OK.

I also do not think that 30 mm scope is any worse for this use.
And for rifles with significant recoil, a bit of extra weight does not hurt.

So which ever you choose will be equally good.

 

[Ridge Runner]

For those claiming 6 power is all that is needed for Dangerous Game I have to ask:

What is the maximum distance on DG are you shooting?

What is your zero range?

My intention is to set a 100 yard zero on my 458WM. Six power didn't provide me the pin point accuracy of shot placement. I changed to a 1-12 power and would much rather use 12 power if shooting out to 100 yards. At 50 yards 6 power was fine.

 

[CoElkHunter]

I have read here where a 30mm scope tube allows for more “internal” adjustment for farther range? My .338 WM is sighted in with my current 1” scope at about 2.5” high at 100 yds. with 225gr bullets. So from really 25yds (bullet crossover) to 300yds., I can aim for a killing heart/lung shot on an elk sized animal without altering my point of aim. I don’t really want to shoot past that distance. So maybe the 30mm tube would be advantageous for someone shooting longer distances? All great information here, just a little confusing.

 

[mark-hunter]

So maybe the 30mm tube would be advantageous for someone shooting longer distances?

This is correct.
But there are two different approaches.

You probably think in "hunting mode", by shooting at game at point blank range, or a bit longer with a bit of holdover if necessary.
This is perfectly OK. But it has its limits.

If we are speaking about long range target shooting, probably you will want maximum clicks (elevation) to bring your crosshair exactly on the bulls eye. 800 meters, 1000 meters, etc. Thats beacause in the lack of clicks, holdover might not give you sufficient accuracy.
Then you will want that your crosshairs are very thin, and adjustment per click as fine as possible (like 1/8 moa click), and you will want all fine adjustments as fine as possible, and to have open turrets so you can apply correction as the environment condition change (like wind, mirage, etc)
For hunting scope, all this is not necessary.

So, it is two different approaches.

Optics makers, adjusted to this 2nd trend, and more often then not started to produce optics with 30 mm tube for general type of hunting. But, there is nothing wrong in 30 mm scope for hunting.
For me personally they even look better.

 

[CoElkHunter]

This is correct.
But there are two different approaches.

You probably think in "hunting mode", by shooting at game at point blank range, or a bit longer with a bit of holdover if necessary.
This is perfectly OK. But it has its limits.

If we are speaking about long range target shooting, probably you will want maximum clicks (elevation) to bring your crosshair exactly on the bulls eye. 800 meters, 1000 meters, etc. Thats beacause in the lack of clicks, holdover might not give you sufficient accuracy.
Then you will want that your crosshairs are very thin, and adjustment per click as fine as possible (like 1/8 moa click), and you will want all fine adjustments as fine as possible, and to have open turrets so you can apply correction as the environment condition change (like wind, mirage, etc)
For hunting scope, all this is not necessary.

So, it is two different approaches.

Optics makers, adjusted to this 2nd trend, and more often then not started to produce optics with 30 mm tube for general type of hunting. But, there is nothing wrong in 30 mm scope for hunting.
For me personally they even look better.

Very interesting! Thanks for explaining this.

 

[CoElkHunter]

Kind of off topic, but are higher scope rings required with a 30mm vs. 1” tube for bolt clearance on a Mauser type action like my CZ which I’m planning to mount a scope on? My Browning has a 60 degree bolt throw, so that would never be an issue.

 

[CBH Australia]

Kind of off topic, but are higher scope rings required with a 30mm vs. 1” tube for bolt clearance on a Mauser type action like my CZ which I’m planning to mount a scope on? My Browning has a 60 degree bolt throw, so that would never be an issue.

Not that i can tell. The centreline of the tube does not change. The ring is just wider at that point accomodating the diameter and the tube sits just lower proportionate to the larger diameter.
The ocular bell and objective bell may need more clearance needing higher rings.
Some people have trouble with the bolt and eyepiece or ocular but thats perhaps limited models not being compatible.

 

[Sika98k]

I doubt you’ll find a better scope for a 375 than a Z8i. It’s a 30mm tube.

Take a good long look at the Schmidt & Bender Exos, 1-8x24. It ticks a lot of boxes.

 

[Philip Glass]

Thanks! But again, the advantage of the 30mm vs. 1”? I have a 2.5x10x 44mm (1” tube) on my Browning .338. Has worked well for many years.

There is more light transmission and more range of adjustment in a 30mm tube. I am just like you and years ago only had 1” scopes. For what you are doing on the guns you mention you will be very happy with a 30mm scope. My personal favorites are Leupold and Swarovski.

 

[Wyatt Smith]

I had tasco and Simmons scopes and liked them. Then I bought a leupold VX2 for 30-06. WOW what a difference. Then I bought an new old stock VX 6 for my 375. The difference between it and the VX 2 was even bigger than the VX 2 and the tasco.
So my theory is that most Americans have only looked through cheap scopes, and therefore don’t notice the difference. For example my friends think Vortex scopes are top of the line. Is it a coincidence that it’s the best scope the farm store ( only place to buy scopes for 50 miles) sells, I don’t think so.

 

[mark-hunter]

When buying optics, this is exactly what you get what you pay for.

 

[BeeMaa]

Kind of off topic, but are higher scope rings required with a 30mm vs. 1” tube for bolt clearance on a Mauser type action like my CZ which I’m planning to mount a scope on? My Browning has a 60 degree bolt throw, so that would never be an issue.

I had a CZ550 375H&H with a Leupold 1.5-5x20 in Warne QR Low rings.
No problem with bolt clearance.
No problem with return to zero.

I need to qualify the above statement.
My rifle was sent to AHR for a #2 upgrade that included straightening the bolt handle.
However, I didn't have a problem with it before I sent it to Wayne.

 

[Dwight Beagle]

It’s been stated 30mm tube scopes have more adjustment range. Not always.

 

[C.W. Richter]

A $250 scope today is as good or better than a $750 scope of 10 years ago. You don't need to spend $1,000 scope. You don't need a Ferrari either. LOL

To an extent, I agree. 'Have $300-$500 Burris scopes on NA/Plains game rifles that have made the aforementioned shots (out to 720 yds! in that case a Barbary Sheep on a cliff in TX. Another at shorter range after dropping the rifle onto a cliff ledge!) However, on the heavier recoiling guns and/or those with specific purposes (DG on heavy calibers in low light, etc.) if you don't shell out the $1,000+ for the right tool, you may be relying too much on your PH's proper equipment to back you up! 'Have had the Leopold 1-5x on thick cover and/or DG guns (lighted, $750,) but upgraded to higher power 30mm glass ($1K on sale.) Prior to selecting the aforementioned Trijicons, 'actually made the trek to EuroOptic and spent quite some time looking through the Kahles, Swaro, Zeiss, S&B, etc. (one of which I thought i'd be purchasing,) but found the iridiums to have the best sight picture, low-light capability and price ($900-1,100) for the 1-6x. Absolutely nothing wrong with the bigger Burris (1" or 30mm x 42/44/50) scopes for longer range work! One advantage of the Burris 1"/50mm scopes is that they do Not require higher bases or rings and they mount very close to the barrel (+0.10-0.125" or so depending on the gun, which further aides in accuracy.)

To your points, I have two OLD Leupold 2-6x and 3-9x 1" that I like to use as a reference point when testing out any new guns and/or handloads for it-and they print very consistently well. Not as great light gathering, FOV, etc. but will get the job done (~$500-$750 nowadays.) 'Have seen many of the 1-5x Leupolds on .375s in Africa. 'Have one on a short pump .30-06 that we use for running game in thick cover and it's phenomenal for that purpose! You could use that $250 scope for plains game hunting...Just have open sights (or a backup rifle), as you may oneday need them!

As far as scopes go, I'd say the S&Bs are Ferraris at $3,000-$4,000 and most of the mfrs mentioned also make military grade scopes in the same price range. $1K-$2K is right on par for a DG rifle scope. $500-<$1,000 is about right for a plains game rifle. Though I own 2-3, 'not a big fan of factory rifles (esp. these days!!!) They're not "Interesting!"

 

[CoElkHunter]

I had tasco and Simmons scopes and liked them. Then I bought a leupold VX2 for 30-06. WOW what a difference. Then I bought an new old stock VX 6 for my 375. The difference between it and the VX 2 was even bigger than the VX 2 and the tasco.
So my theory is that most Americans have only looked through cheap scopes, and therefore don’t notice the difference. For example my friends think Vortex scopes are top of the line. Is it a coincidence that it’s the best scope the farm store ( only place to buy scopes for 50 miles) sells, I don’t think so.

Other than my father in law’s older Leupolds and his buddy’s high dollar Vortex spotting scope (very clear!), I’ve only owned/looked through cheaper glass like my mid 90s Simmons Aetec on my .338 or Bushnells. Guess I never had a reason until now to want/need something better as the Aetec has worked well for me. I didn’t really notice better clarity with the Leupold, but I guess the Simmons’ scopes of today aren’t built as well. Mine has been used a lot in adverse weather and my buddy took it to Newfoundland hunting for a week bouncing around on a four wheeler (guess that’s how they hunt there?) in torrential rain and it still holds a zero. Just lucky with that scope I guess, But, I have the aforementioned larger bore rifles now and want to upgrade to more reliable scopes. I think I’ll check out the clarity of different brand scopes locally and then look for a sale price on the one which works best for me. Other than elk hunting this fall, I’ll have time now to decide if I choose to take my rifle(s) for an African hunt.

 

[Ray B]

One aspect of scope tubes that I'm disappointed in is the internal adjustment. I got a Leupold VX6 4-24x scope with the idea of long range target shooting. It was for a 375 RUM using Sierra 350 gr HPBTM bullets. The BC is .8+ and MV near 2700 fps. So the trajectory is quite flat even considering the relatively slow MV. I got the custom elevation dial, zeroed the scope at 300 yards and installed the dial. It has graduations to 1050 yards however the scope runs out of adjustment at 450 yards. This is with a 34mm scope tube. I sent it back to Leupold about it. They inspected the scope and said it was in fine working order and that what i needed to do is get scope bases to tile the scope to increase the elevation. I needed 40 MOA but they do not offer such a base and said that i should look elsewhere. So I will, but I'll also look elsewhere for a scope.

Regarding brightness, I compared it awhile back to several 1" tube scopes and it was a few minutes longer at sunset for picking out detail, but for all the size, I prefer a lighter scope than the few minutes extra at dusk.

 

[Dr Ray]

I have 1” scopes on all of my rifles for the hunting I’ve done in North America forever. I’ve read here a lot where 30mm tubes are recommended? Are they worth the extra weight and/or better for lower powered scopes? I’m asking because I have a .375 and .416 I’m wanting to put scopes on. Thanks!

I don’t use any 30mm anymore as I find the extra weight and what I call cumbersome = not worth the effort.
Mind you if I were doing very long range varmint shooting that would be different.
I now go for sleek and compact.
I use/d 1.4-5 Leupold scopes on those calibers.

 

[Bob Nelson 35Whelen]

Fair enough, I didn’t answer the question. Per Swarovski:

A scope's EP corresponds to your own pupil, which dilates from about 2mm in bright sunlight to perhaps 7mm in the dark. If your scope's exit pupil is smaller than your pupil, it can't transmit all the light you can use. If it's larger, the extra rim of light bounces off your iris and never enters your pupil to stimulate your retina. Wasted light. But an excess diameter of exit pupil does give your eye more room to wander around in without showing edge blackout, so that's something.

The reason a 30mm main tube scope isn't inherently brighter than a 1-inch scope is because both carry internal lenses much larger than 7mm, so there is no loss of light through either. The reason some 30mm scopes appear to project brighter views is probably because they were built with the absolute finest materials and effective light transmission (how much light the scope passes through) determines brightness, is a product of the number of air-to-glass surfaces in the scope (the fewer the better) and the anti-reflection coatings on those lenses. (The more the better.)

So what, then, are the advantages of a 30mm scope tube? The walls can be made thicker for added strength and durability or the internal lenses can be made slightly larger, which increases optical performance simply because larger lenses always perform better than smaller ones, all else being equal. Alternatively, manufacturers can keep internal lenses the same size as those in their 1-inch scopes and use the extra internal room for long range reticle adjustments.



2.5-10 is totally appropriate for a 338 but I think it is a bad choice for a 375 or a 416 unless it will be used exclusively on plains game or the scope will be removed for close in work, assuming one has time. True 1x allows best performance of a scope up close.

@Bert the Turtle.
Tube diameter has zip to do with light transmission and exit pupil.
Objective diameter divided by magnification. So a 10x40 will give an exit pupil of 4mm while a 10x 50 will give 4.5 mill. The quality of the lens coating also affects the amount of light transmission. At the moment Meopta are the industry leaders with 92% overall for a 3.5 to 10x44 or over 98% per lens.
On a Harvey kicker like the 416 the old Leopold straight 3x reigned supreme.
The advantage of a 25mm over a 30mm tube is they are lighter and are less likely to move in the rings under recoil than a heavier 30mm tube.
The 30 mms tube give more bondage and elevation adjustment but for the average hunter it is wasted.
The older I get the more I feel the extra weight even if it's only a few ounces here and there it soon adds up.
Bob

 

[Bob Nelson 35Whelen]

Just a heads up, the Vortex lower level scopes are made in China, i.e. junk. But hey, they have a great warranty! When it goes tits up in Africa, you'll be able to get it fixed when you get back.

Seriously, 30 & larger tubes generally allow more adjustment. For example, the Nightforce NXS line has 100 moa of elevation and 60 moa of windage.

@Hogpatrol
Realistically unless you are doing long range shooting do you need 100moa and 60moa of adjustment.
If your scope is mounted properly in the first place 4 to 5 moa is more than ample to get zeroed. If you have windage adjustable mounts you need even less. Once my rifles are zeroed depending on my rifle I know I'm fine out to 400yards which is further than I should be shooting game at anyhoo.
Just my thoughts as a hunter not a long range shooter.
Bob