Ideal scope height?

[Wolverineshooter]

I read somewhere that you should put the scopes as close to the barrel as you can. That's what I have always tried to do. But on a second thought does it really matter much?

I used the Chairgun and did some calculations. Raising the height by .5 inches may push the zeros further by two to three yards,  the pellet drop at 100 yards will be reduced by 2 inches. Which could be a good thing since most hunting or paper Punching are more than 10 yards away anyway.

So I am wondering what are the rationals for keep the scope low? Certainly the torque on the rings will be lower with lower ring height and less shock to the scope. Is this why people want to keep the scopes low?

[Wolverineshooter]

Well I found something that makes sense to me.

There are good reasons not to mount a scope as low as possible. The reasons I can see for keeping a scope as low as possible above the bore include minimizing the torque on the rings when the gun is fired, making the scope less likely (maybe) to get caught on brush while being carried, and perhaps to keep the shooters head as low as possible on a battle rifle.

The main concern as to how high a scope should be mountd in my opinion is that the scopes optical axis should be comfortable for the shooter. Either too low or too high will be uncomfortable and won't give a proper "cheek weld" . If "tight to the barrel" is the most comfortable position maybe the rifle's stock needs a higher comb. Obviously the shape of the stock's comb relative to the bore matters. So does the relative shape of the shooter's face, neck, and shoulders, so there's no "right" answer to the exact distance a scope should be mounted from the barrel. On certain classes of firearms a scope needs to be mounted beside the barrel, not above it. An example is a shoulder fired recoilless rifle, or grenade launchers like the M70 and M203.

Reasons for raising the scope include the fact that if a rifle is set up to maximize the "point blank" range such that from zero out to some maximum distance a bullet will fall in a given diameter circle if the sights are aimed at the center of the circle, then the scope height above the bore should be equal to the radius of that circle. That could be rediculous if a very large or very small point blank error diameter is desired but it makes sense for a 5 or six inch diameter circle.

Mounting a scope high also puts the bore lower relative to the shoulder, and assuming the stock is designed for it, reducing the rotational recoil moment when a gun is fired. That helps reduce muzzle flip. The AR-15 is an example of a rifle designed with this and the previous reason in mind. The M14 and M1 were not.

Another reason to keep the scope high is that thermal distortion from warm air rising off a heated barrel is more likely to miss being in the line of sight the higher the scope is mounted if there is any crosswind.

There is a slight increase in sensitivity to canting by mounting a scope higher. On the other hand it's easier to notice that a rifle is canted with the scope mounted higher.

[Horatio]

I like lower more than higher.

Higher messes up your near zero.  If all your shooting is at a bait station of known distance, no big deal. But for a more effective point blank zero for general purpose, lower is better.

Muzzle flip? I don’t envision fighting it out at BenGhazi anytime soon. If life came to that, send just enough downrange to get the other sides head down and get out fast.

[rsterne]

I prefer as low as possible, partly because most stocks are too low anyways to provide a proper cheek weld.... Cant is also less of an issue, mechanical strength is better, and we don't have to worry about recoil or mirage.... While a higher mount does move the near and far zeros further out, which can be beneficial in some cases.... it really increases what happens between the near zero and the muzzle to the POI / POA relationship.... Grouse hunting, for example, sometimes gives you surprise shots at very close range, and a high scope requires more hold-over to insure you don't shoot under the target....

Bob

[Horatio]

Yes^

My experience also, even with a center fire rifle, your near zero is messed up far more than your far zero is extended.

[nced]

I read somewhere that you should put the scopes as close to the barrel as you can. That's what I have always tried to do. But on a second thought does it really matter much?

I used the Chairgun and did some calculations. Raising the height by .5 inches may push the zeros further by two to three yards,  the pellet drop at 100 yards will be reduced by 2 inches. Which could be a good thing since most hunting or paper Punching are more than 10 yards away anyway.

So I am wondering what are the rationals for keep the scope low? Certainly the torque on the rings will be lower with lower ring height and less shock to the scope. Is this why people want to keep the scopes low?

I used to keep my scopes close to my R9 receivers so there would be minimum pellet rise from my muzzle to the line of sight at my 30 yard zero distance. When shooting hunter class field target matches I do "rangefinding by scope focusing" and since focusing a scope at the closer distances (10-30 yards) is pretty accurate I wanted the flattest trajectory for these targets that aren't affected as much by atmospheric conditions as distances past 30 yards. LOL....when I had an old Japanese 3-12x40 Bushnell Trophy mounted to my .177 R9 I needed to cut a piece out of the bottom of the front lens shade so it could be slipped over the AO of the mounted scope.

When the scope is set higher the "trajectory curve" is benefited at the further distances. Since the field targets set at the longer distances have larger killzones and really aren't a high percentage of the targets set out I personally find it better to favor the low mount for the majority of targets set out.

There are a couple things that play out in the scope height issue. One is the gun used be it piston or PCP since a PCP can be set up to shoot heavy pellets at velocities the piston gun can use with lighter pellets. The higher BC of a heavy 10.5 grain pellet at 880fps allows a flatter trajectory curve than a lighter 7.9 grain pellet at 880fps which may be part of the consideration when choosing scope height. Another issue when shooting "critters" is the fact that unlike the field targets set on a lane.......the kill zone of a squirrel doesn't change with distance. The head if a squirrel will have a killzone about the size of a nickel (IMHO) regardless if it's at 8 yards or 50 yards. It's for this reason that I seldom take shots at tree squirrels past 30 yards and another reason why I use a scope mounted close to the receiver.

I currently can't mount my scope center at the same height as in the beginning because I used to get by using a "low mount" with my 1" tube scopes with 40mm AO, however I currently need a high mount for my 1" (or 30mm) tube scopes with a 50mm AO........


LOL....I'm currently using this Weaver to dovetail adapter plus a set of Weaver rings......



Makes it easy to swap out scopes without loosening/tightening a bunch of screws and allows the use of a lower scope ring, however this pic shows that the 50mm objective is still pretty close to the receiver so the actual optics and mounts may restrict your actual scope height.

[CraigH]

I prefer low mounting and go for as low as possible especially on guns used at short distances.   There are often advantages at long distances with higher scope mounting.   External ballistics also plays an important role and has to be considered.   Chairgun is very useful for a graphic representation.

(Much of this popped up above while I was making this post)

[Wolverineshooter]

For short distances I agree that lower mounts are preferred because the benefits offered by high mounts are not needed, namely, the extended zero range.

But if you have a powerful gun shooting some thing furth out, then a high mount may make sense. Although with drawbacks on recoil.

[bandg]

I usually mount mine as high as I can and still maintain a comfortable shooting position.  MPBR is something I always try to maximize.  If one is shooting at very close ranges very often then lower would almost certainly be better but I almost never shoot at a very close target with a scoped rifle.  Considering target size is also relevant.  The smaller the common target for a specific shooter, the more a lower mounting scheme should benefit them.

[Wolverineshooter]

I usually mount mine as high as I can and still maintain a comfortable shooting position.  MPBR is something I always try to maximize.  If one is shooting at very close ranges very often then lower would almost certainly be better but I almost never shoot at a very close target with a scoped rifle.  Considering target size is also relevant.  The smaller the common target for a specific shooter, the more a lower mounting scheme should benefit them.

Thanks. Sorry for my ignorance but what MPBR stands for?

[nervoustrigger]

Maximum point blank range, where the apex of the trajectory is out as far as possible.  All distances besides that will be holdover, never hold under.  Generally in the vicinity of 25 or 30 yards.

[rsterne]

Something that hasn't been clarified here is that as you increase the scope height, although it extends the ranges at which the PBR occurs....  it SHORTENS the difference between the two (known as the Maximum Point Blank Range, or MPBR).... The PBR is where you can hold "dead on" and have your shots fall within the Kill Zone (KZ).... As an example, for my Hatsan AT-44 Long in .25 cal., shooting a 34 gr. pellet (BC 0.050) at 955 fps.... with a 1/2" KZ, using ChairGun....

1.5" Scope height.... Near PBR = 13.5 yds.... Optimum Zero = 38.6 yds.... Far PBR= 42.9 yds.... MPBR Range (difference) = 29.4 yds (68.5% of Far PBR)....

3.0" Scope height.... Near PBR = 23.4 yds.... Optimum Zero = 47.8 yds.... Far PBR = 51.9 yds.... MPBR Range (difference) = 28.5 yds (54.9% of Far PBR)....

Just something else to consider....

Bob

[CraigH]

Good Stuff!   I only recently started using Chair Gun and if it is only reasonably accurate, it is great.   Really gives the ability to quickly analyze many variables (in this topic scope height) and get starting point(s) for actually shooting.

On Window 10 a bit of computer learning was needed to get the installation to run.

[nced]

Good Stuff!   I only recently started using Chair Gun and if it is only reasonably accurate, it is great.   Really gives the ability to quickly analyze many variables (in this topic scope height) and get starting point(s) for actually shooting.

On Window 10 a bit of computer learning was needed to get the installation to run.

Same here.

I do use ChairGun to get a vague idea of the trajectory differences before testing different tune levels, however "actual trajectory plotting" at my 53 yard back yard lane is a necessity. For me CG data isn't accurate enough to use "as is" with my recoiling springer but the output is "reasonably accurate" for "rough trajectory calcs".

[Wolverineshooter]

On Window 10 a bit of computer learning was needed to get the installation to run.

What did you do to install on Win 10? I was not able to do it.

[Fussell]

Ever since I started shooting FT, I like my scopes kind of high off the bore. I've centered my Sightron a good 3" above the center line of the bore.

I shoot unlimited class, because my crappy eyesight needs at least 30 power to be half way competitive. The 3" height has it's drawbacks for shooting inside 15 yds.

I use hold overs and don't click, so I have to hold over 7 stadia or 14 MOA on the cross hairs at 10yds.

Here's my holdover chart for 3" above the bore shooting 13.4 gr JSB Monsters at 818 FPS with a 28 yd zero

yds      stadia
10         7
11         6
12         5
13         4.2
14         3.5
15         3.0
16         2.5
17         2.0
18         1.5
19         1.2
20         1.0
21         .7
22         .5
23         .3
24         .1

pretty much flat out to 37.5 yds

40          .2
42.5       .5
45          1.0
47.5       1.2
50          2.0 
55      I still use 2.0 stadia 

Now here's the kicker. Since AAFTA rules state the kill zone must be 1.5" beyond 45 yds I'm using the high scope mount to help me with this. You see, I've found out that I can use a 2 stadia hold over at anything between 50 and 55 yds and still make it inside that 1.5" KZ most of the time.

 I hold 2 stadia at fifty and it shoots a little high into the kz. I hold 2 at fifty five and it shoots a little low into the kz.  Nine times out of ten this works for me, so I'm sticking with it. I've barely eeked into the 50 club the last several matches by doing this. Now if I could just make myself practice off hand shooting ;-)

I have a really hard time range finding correctly beyond the 47 yd mark is the reason I do it like this.



   

[CraigH]

On Window 10 a bit of computer learning was needed to get the installation to run.

What did you do to install on Win 10? I was not able to do it.

The CG install went perfectly well and a desktop icon was created, but when clicking it a small box popped up with an error about no Java home (or something similar) and to install either JDK or JRE - meaning to me 

So in my unorganized, undocumented way, I to www.java.com and downloaded the "Recommended Version 8 Update".     After that the same error occurred so I searched the web for information on java home and environment variables.   But various references did not provide the answer as the "Control Panel" has no submenu that the references stated.   I used the Windows 10 "Search" button next to the "Windows" button and entered "environment".   That returned "Edit the system environment variables" which when selected brings up  a request to enter the admin password and then a window comes up with "Environment Variables" in the lower right corner.  Select that and the system variables are displayed.   At this point I did not know where the Java installation was placed, but I finally located that in "C:\Program Files (x86)\Java".   SO - select "New..." which brings up another window and enter Variable name "EXE4J" and Variable valve "C\Program Files (x86)\Java"  (no quotes), and select OK in this window and the previous window.    Now selecting the Chair Gun desktop icon should start Chair Gun.

Note:  I discovered that any images created from Chair Gun are placed in C:\ProgramData\ChairGun4\Images.

Hope this helps.    The vagaries of Windows paths still confuse me a bit.

[Wolverineshooter]

On Window 10 a bit of computer learning was needed to get the installation to run.

What did you do to install on Win 10? I was not able to do it.

The CG install went perfectly well and a desktop icon was created, but when clicking it a small box popped up with an error about no Java home (or something similar) and to install either JDK or JRE - meaning to me 

So in my unorganized, undocumented way, I to www.java.com and downloaded the "Recommended Version 8 Update".     After that the same error occurred so I searched the web for information on java home and environment variables.   But various references did not provide the answer as the "Control Panel" has no submenu that the references stated.   I used the Windows 10 "Search" button next to the "Windows" button and entered "environment".   That returned "Edit the system environment variables" which when selected brings up  a request to enter the admin password and then a window comes up with "Environment Variables" in the lower right corner.  Select that and the system variables are displayed.   At this point I did not know where the Java installation was placed, but I finally located that in "C:\Program Files (x86)\Java".   SO - select "New..." which brings up another window and enter Variable name "EXE4J" and Variable valve "C\Program Files (x86)\Java"  (no quotes), and select OK in this window and the previous window.    Now selecting the Chair Gun desktop icon should start Chair Gun.

Note:  I discovered that any images created from Chair Gun are placed in C:\ProgramData\ChairGun4\Images.

Hope this helps.    The vagaries of Windows paths still confuse me a bit.

Craig, that is genius, it worked!

I do not know how you figured this out but without your help I will have no clue. Thanks!

[mobilehomer]

There is an easier method. Uninstall Chairgun, install Java, then reinstall CG.

[CraigH]

I'm sure there was.   But not known here.   Thanks!   

Greg,

You're welcome!!!