Optimal scope height study



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Offline Scotchmo

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Optimal scope height study
« on: November 12, 2018, 07:54:44 PM »
Typically, I have mounted my scopes as low as possible. We have tended to have a lot of 3/8” targets at Western GP matches, and by necessity, those targets tend to be set at fairly close distances. High scopes can greatly exacerbate ranging errors for those close targets. Lately I have gone to slightly bigger scopes mounted slightly higher. I know that will help some of my longer shots so it should make up for an occasional miss on the closer 3/8” targets.

When you look around at other shooter's equipment, you'll see very high scopes, especially among some of the WFTF shooters. I know the World match WFTF courses don't have 3/8” reduced targets, and the WFTF course rules allow only a few of the 1” (25mm) and 0.59” (15mm) targets on any given course. So you will never see a close target with a very high degree of difficulty at a World match. Most of the targets are full size 1.575” (40mm) and they tend to set them farther out.

I'm planning on shooting in the 2019 WFTF world match and decided to look into some changes to my FT setup. One of those possible changes would be scope height. I used a 2.3” high scope (high for me) this last season. But I see others with much higher scopes.

What is the optimum scope height? The empirical evidence suggests that for WFTF, it's certainly higher than 2.3”, so I just got some higher mounts and am now at 2.6”. That did not seem very scientific. I figured there must be a way to quantify it. The hit probability of any given target is based on a few factors. One of those factors is ranging error. Scope height determines at what distances ranging errors are most detrimental. Targets near your zero are more tolerant of ranging errors. I decided to keep it simple to start and determine targets distances vs scope height for typical field target courses when shooting at 12fpe. Whenever you get away from your zero, you need to click (or holdover) more. Those distances with more clicks are more subject to ranging errors.

I made a spreadsheet where I could input all the target distances of an FT course. It takes scope height, and pellet velocity and BC, and calculates the amount of clicks (holdover) at each target, and totals those clicks for the whole course. More clicks means more potential errors from mis-ranging. For any given course, I can very the scope height and look for the height that yields the lowest  total clicks for the entire match.

The results were interesting.

The trajectory parameters were 795fps and .023 BC. For a typical AAFTA GP course (Western States), the spreadsheet shows an optimal scope height of 2.0”.

Last year, our club set a WFTF legal course for our GP. Though we did use the maximum number of 15mm and 25mm reduced targets that WFTF allows. The optimal scope height for that course was 2.1”.

I also input the three World courses from 2018 Poland.
White course – 3.6” optimal scope height
Blue course – 3.8” optimal cope height
Black course – 2.8” optimal scope height

The Black course had a lot more reduced targets than the White and Blue courses. The strange thing is that all the courses had more reducers than are allowed by the published WFTF course rules. I don't think more reduced targets is a bad thing, but it is bad when the course is not what is specified by the rules.

I now have a 2.6” high scope vs the 2.3” high scope that I used all off last year. 2.6”should be a better compromise for the AAFTA GP circuit and the Worlds match. Though probably a little low for a typical Worlds course. I'm just not ready to go with a 3+” high scope.

I know that you can't necessarily rely on the course rules for target size, visibility, distance, etc. Some times the shooter has recourse when they encounter an illegally placed target, other times they don't. It happens in the USA and at the Worlds. So best to be prepared.
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Offline Motorhead

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Re: Optimal scope height study
« Reply #1 on: November 12, 2018, 09:05:49 PM »
Even tho we shoot smaller KZ's up close more so than the Europeans,  I'm still of the mind set that the advantages of trajectory arc correction being somewhat flatter further out with high scope mounting, i simply am NOT willing to have the correction in close so critical doing so.  After 3 years now shooting .20 caliber at the 790's velocity which is similar to WFTF 12 ft lb speeds ( and trajectory profile too ) have had No Problems dropping into the KZ on far targets using a SH of 1.8" .... go figure being we've been ranging at 12x for 2 season and 16x in 2018.  With the ranging capability of the high mag scopes allowed in WFTF, WHY CHANGE WHAT YOUR ACCUSTOMED TOO ???  and just take advantage to superior ranging you will have at higher magnification and shoot how you know how too !!

JMO ...
Scott 
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Offline Scotchmo

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Re: Optimal scope height study
« Reply #2 on: November 12, 2018, 11:44:30 PM »
Motorhead,

I have a similar aversion to high scopes. Doing what I'm accustomed to could work. But I am going to the world's next year. And the courses will likely be different then I'm accustomed to. So I am considering some changes.

I have been ranging at 24x for most matches the last 4 years. Better than 12x or 16x but still not ideal, especially when it gets windy.

In the past, most of my guns have had a scope height of 1.7" to 2.1". This last year, 2.3" has not been a problem for close shots, especially when the smallest is .59" (15mm). I'll try 2.6" next, but I'll switch back if it doesn't work out.
« Last Edit: November 12, 2018, 11:49:18 PM by Scotchmo »
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Offline Scotchmo

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Re: Optimal scope height study
« Reply #3 on: November 12, 2018, 11:58:33 PM »
Motorhead,
I ran the following through my spreadsheet:
795fps
.035 BC

Using the course layout from a Western States GP match, the optimal scope height ends up being 1.8" . That's probably not a coincidence that you like 1.8" .
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Offline gokidd

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Re: Optimal scope height study
« Reply #4 on: November 13, 2018, 11:14:47 AM »
... and then there is the dreaded "I forgot after I shot that close target and was one full turret rotation wrong for the next lane"
Danggit.
It's tough being forgetful.
W(f)TF!!

Thank you for that info, Scott H. I always appreciate both your science and your willingness to share.
B
« Last Edit: November 13, 2018, 11:17:19 AM by gokidd »
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Offline Bryan H.

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Re: Optimal scope height study
« Reply #5 on: November 13, 2018, 11:24:45 AM »
So, you can shoot WFTF HFT with 16X now?
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Offline nced

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Re: Optimal scope height study
« Reply #6 on: November 13, 2018, 11:48:14 AM »
So, you can shoot WFTF HFT with 16X now?
WFTF has no scope power limit and it also aliows "clicking on".

HFT however has a 16x max power setting (as of the past year) but "clicking on" isn't allowed.

Here is the 2018 AAFTA Handbook...........
http://www.aafta.org/Assets/handbook/2018/AAFTA_Handbook_2018.pdf

Offline Motorhead

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Re: Optimal scope height study
« Reply #7 on: November 13, 2018, 12:11:58 PM »
So, you can shoot WFTF HFT with 16X now?

WFTF along with OPEN class are unlimited on X magnification. ( Can shoot holdover or clicking )
HUNTER classes had been at a 12X limit until the 2018 season where the limit was raised to 16x ( Can ONLY shoot holdover .. NO clicking allowed )
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Offline Bryan H.

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Re: Optimal scope height study
« Reply #8 on: November 13, 2018, 12:16:31 PM »
I was just looking at WFTF rules and I could not find WFTF rules specific to HFT.  Gonna check that kink out right now.  Thanks Ed.
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Offline Bryan H.

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Re: Optimal scope height study
« Reply #9 on: November 13, 2018, 12:17:07 PM »
So, you can shoot WFTF HFT with 16X now?

WFTF along with OPEN class are unlimited on X magnification. ( Can shoot holdover or clicking )
HUNTER classes had been at a 12X limit until the 2018 season where the limit was raised to 16x ( Can ONLY shoot holdover .. NO clicking allowed )

Thanks
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Offline Motorhead

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Re: Optimal scope height study
« Reply #10 on: November 13, 2018, 12:36:54 PM »
I was just looking at WFTF rules and I could not find WFTF rules specific to HFT.  Gonna check that kink out right now.  Thanks Ed.

There is NO WFTF / Hunter class ... they are SEPARATE classes entirely having there own specific rules ... tho shoot the same course here in the USA
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Offline DRAGON64

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Re: Optimal scope height study
« Reply #11 on: November 13, 2018, 01:50:05 PM »
When you are talking about scope height, are you referring to center line of scope in relation to bore?  I recently picked up a 60mm objective scope, and are currently trying to figure what I would need in the way of scope rings for proper scope height.  I too will be shooting WFTF rules here stateside.
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Offline Scotchmo

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Re: Optimal scope height study
« Reply #12 on: November 13, 2018, 05:03:10 PM »
So, you can shoot WFTF HFT with 16X now?

WFTF HFT?

No such thing. But there is a WHFT (World Hunter Field Target), and they have no magnification limit for scopes. Though I'm only aware of one club in the USA that has HFT matches (Heflin, Alabama). That type of course would favor a low mounted scope.

AAFTA Hunter Division is not really HFT, though many in the USA mistakenly call it HFT.

HFT - no scope limit
AAFTA Hunter Division - 16x scope limit

https://www.whfto.com/
https://www.facebook.com/whfto/
« Last Edit: November 13, 2018, 05:13:08 PM by Scotchmo »
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Offline Scotchmo

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Re: Optimal scope height study
« Reply #13 on: November 13, 2018, 05:09:15 PM »
When you are talking about scope height, are you referring to center line of scope in relation to bore?  I recently picked up a 60mm objective scope, and are currently trying to figure what I would need in the way of scope rings for proper scope height.  I too will be shooting WFTF rules here stateside.

The 12fpe WFTF limit will have some bearing on scope height. The very high scopes are not really needed on most USA courses. At USA AAFTA matches, you will see more close targets, and they will be more difficult (0.375" for AAFTA vs 0.59" for WFTF). The course layout has even more affect on optimal scope height than does the power level (12fpe vs 20fpe).

You'll sometimes need higher scope rings to clear the large objectives. On most USA courses, about 2" - 2.1" high should be near optimal.
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Offline 22Jim

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Re: Optimal scope height study
« Reply #14 on: November 16, 2018, 01:01:05 PM »
The 12fpe WFTF limit will have some bearing on scope height. The very high scopes are not really needed on most USA courses. At USA AAFTA matches, you will see more close targets, and they will be more difficult (0.375" for AAFTA vs 0.59" for WFTF). The course layout has even more affect on optimal scope height than does the power level (12fpe vs 20fpe).

I see why you are researching this now. I looked at the course details from Poland and see where scope height could help pick up a couple of points over the course of the match. 89 of 150 targets were over 40 yards, only 24 targets were under 30 yards and 11 of those were forced position. The long game appears to be everything in Euro WFTF matches.

I really like your method of evaluating optimum scope height. I never gave it much thought as I always favored the lowest position I could get which on my competition rifles was always between 1.8 and 2.1 inches. Based on your analysis that seems to be optimal for US FT courses.

Thanks,
Jim in Sacramento
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Offline Scotchmo

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Re: Optimal scope height study
« Reply #15 on: November 16, 2018, 05:17:32 PM »
...
I really like your method of evaluating optimum scope height. I never gave it much thought as I always favored the lowest position I could get which on my competition rifles was always between 1.8 and 2.1 inches. Based on your analysis that seems to be optimal for US FT courses.

Thanks,
Jim in Sacramento

880fps with AA/JSB heavies (10.3gr/.031 BC) on a typical Western AAFTA course, it ends up as 1.5" high. Hard to do with most scopes/mounts, so lowest height will likely be determined by objective size and available mounts. My 18fpe Marauder is at 1.72" scope height.
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Offline HectorMedina

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Re: Optimal scope height study
« Reply #16 on: November 17, 2018, 02:36:47 PM »
Scvott;

Very interesting, but it begs a question:

WHERE are you measuring the "height". żAre we talking SCOPE height? OR żAre we talking LOS height?

PP Calc uses LOS height, so it is measured/calculated/corrected to the muzzle.

I find that 2.5" to 2.6" at the saddle is a good height, as the BALANCE of the gun is more manageable. Going to 3" and more makes my gun feel "tippy" and that is more important than the theoretical optimum scope height.

JMHO


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Offline Bryan H.

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Re: Optimal scope height study
« Reply #17 on: November 17, 2018, 03:15:54 PM »
I am highly opinionated when it comes to scope height, especially on a springer.  Especially for someone that has not/does not compete.  For me, the lower the better.  Will be watching this thread closely! 
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Offline Greg5850

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Re: Optimal scope height study
« Reply #18 on: November 17, 2018, 03:40:21 PM »
My scope is 2.6 in high.  That’s from center barrel to center scope.  Part of the equation for me is a comfortable head position, and as Hector said “ not too “tippy”.  Some of the Brits experimenting with very high scopes have come back down a bit.

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Offline Scotchmo

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Re: Optimal scope height study
« Reply #19 on: November 17, 2018, 11:54:31 PM »
Scvott;

Very interesting, but it begs a question:

WHERE are you measuring the "height". żAre we talking SCOPE height? OR żAre we talking LOS height?

PP Calc uses LOS height, so it is measured/calculated/corrected to the muzzle.

I find that 2.5" to 2.6" at the saddle is a good height, as the BALANCE of the gun is more manageable. Going to 3" and more makes my gun feel "tippy" and that is more important than the theoretical optimum scope height.

JMHO


HM

I measure the scope height at the scope (at the erector tube gimbal to be exact), but I do correct for the scope-base (distance from gimbal to muzzle crown). Projectile drop is calculated from the muzzle crown to the target. And target distance is measured from the gimbal to the target.
« Last Edit: November 17, 2018, 11:56:33 PM by Scotchmo »
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