"how can I shoot straighter" scope height and "Maximum point blank range"

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Someone asked in the title of another thread, "how can I shoot straighter". My initial thought was raise your scope up. In case anyone has not seen this, here is a link to "Maximum point blank range". If you thumb through the four pages, you can get a good (basic) understanding of the affect of scope height and how to select the correct range to zero your rifle based on the size of your target. Click on the "OPBZ math" to do sample calculations.
http://www.arld1.com/images/swfs/trajectorypbr2.swf
This will (partly)explain why IHMSA standing silhouette shooters use scope mounts that look like this:
XP-100.jpg

Hunting rifle scope mounts will not be quite so high but the higher mount "flattens" the trajectory.
White Feather
 
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Silhouette shooting is an incredibly specialized discipline. It's the only place you are going to see scopes mounted way high like in that photo. I don't think it's any kind of answer to the question "How can I shoot straighter". Mount a scope too high and you lose any sort of repeatable cheek weld.
 
Silhouette shooting is an incredibly specialized discipline. It's the only place you are going to see scopes mounted way high like in that photo. I don't think it's any kind of answer to the question "How can I shoot straighter". Mount a scope too high and you lose any sort of repeatable cheek weld.

A scope mount that high also defeats the purpose of a rifle: more points of contact with you the shooter, thereby increasing stability (vs a pistol) when shooting offhand.
 
the higher mount "flattens" the trajectory.

This may be the dumbest thing I've heard all year (and year is almost up).

You could put a high mount, a sink, a pig, and a magnet on top of the rifle and it won't change the trajectory. The trajectory has to do with the rifling, bullet weight, powder, bullet shape, and bullet speed (powder). Now perhaps mounting it that high will let you balance the pistol/rifle better on your body, or raise the scope to the apex of the bullet's trajectory, but it won't change it. If you have a very hot fast round, it is flat shooting already, so instead of an inverted U shape it has a more flatter beginning, is flat longer, and then falls off fast near the end. Raising that scope basically brings you level to the flat portion of the trajectory, which may make up 75% of the flight path within a certain range (lets say 300 yards?) depending on the factors discussed.

Also, if you look at most sniper rifles, they put their scopes AS LOW as possible to the barrel. This is not just for cheek weld, but to also get the scope as close to the bore as possible, which simplifies a lot of calculations. They may have a downward cant (20MOA, 30MOA) so that there are enough adjustments available to reach out far, but that is strictly based on the round, the range you want to make, and how much adjustment range your scope has (wider scopes have more, such as 34mm or 40mm).
 
The trajectory has to do with the rifling, bullet weight, powder, bullet shape, and bullet speed (powder).

I would add "angle of departure" (sometimes called "angle of elevation") to the factors than influence trajectory.
 
I would add "angle of departure" (sometimes called "angle of elevation") to the factors than influence trajectory.

This is true, good point. Gravity has a lot to do with it, so the angle would squeeze the shape or elongate it, depending on up or down (sort of how they make range finders for bowhunters shooting down from a stand).
 
This may be the dumbest thing I've heard all year (and year is almost up).

You could put a high mount, a sink, a pig, and a magnet on top of the rifle and it won't change the trajectory. The trajectory has to do with the rifling, bullet weight, powder, bullet shape, and bullet speed (powder). Now perhaps mounting it that high will let you balance the pistol/rifle better on your body, or raise the scope to the apex of the bullet's trajectory, but it won't change it. If you have a very hot fast round, it is flat shooting already, so instead of an inverted U shape it has a more flatter beginning, is flat longer, and then falls off fast near the end. Raising that scope basically brings you level to the flat portion of the trajectory, which may make up 75% of the flight path within a certain range (lets say 300 yards?) depending on the factors discussed.

Also, if you look at most sniper rifles, they put their scopes AS LOW as possible to the barrel. This is not just for cheek weld, but to also get the scope as close to the bore as possible, which simplifies a lot of calculations. They may have a downward cant (20MOA, 30MOA) so that there are enough adjustments available to reach out far, but that is strictly based on the round, the range you want to make, and how much adjustment range your scope has (wider scopes have more, such as 34mm or 40mm).
Here is a simple explanation that doesn't require sinks, magnets, or pigs:
http://www.opticstalk.com/scope-mount-height_topic18514.html
One slight advantage of a higher scope mount is that it flattens trajectory. This isn’t actually so, of course, since trajectory of a given load remains the same under the same conditions. What higher mounts do, however, is slightly raise the angle of the bore in relationship to the line of aim.
Let’s say, for instance, that our 7mm-08 has a scope mounted 1-1/2” above the bore. If we sight it in 2” high at 100 yards, a typical 140-grain load will land just about where we aim at 200 yards.
However, if the scope is mounted 2” over the bore, the angle between the bore and the line of aim is increased slightly, because the bore is now ½” further below the reticle. If we sight in 2” high at 100 yards, this extra ½” means that our bullet will land an inch high at 200 yards, instead of right at point of aim. This is because raising the height of the scope ½” at the rifle has the same effect as raising the point of impact ½” at 100 yards.
The bullet will also now land 1-1/2” higher at 300 yards (3 times ½”) and 2 inches higher at 400 yards than it would with a scope mounted only 1-1/2” above the line of bore. This isn’t much but it’s noticeable, and more so with some cartridges. With a load like the 140-grain 7mm-08, with the bullet starting at 2800 fps, it’s about like increasing the muzzle velocity 100 fps. With a faster cartridge, say the 7mm STW shooting the same 140-grain bullet at 3300 fps, an extra half-inch of scope height has the same effect as increasing the muzzle velocity about 200 fps.
Of course we could also raise the height of the 100-yard sight-in ½” and gain the same effect. Or do we? Not really, because with higher mounts the bullet’s trajectory will remain closer to the line of aim, so the risk of shooting over an animal is reduced. This is why I often use fairly high-mounted scopes on varmint rifles.
You learn something new every day. Unless you already know it all...[wink]
White Feather
 
Here is a simple explanation that doesn't require sinks, magnets, or pigs:
http://www.opticstalk.com/scope-mount-height_topic18514.html
One slight advantage of a higher scope mount is that it flattens trajectory. This isn’t actually so, of course, since trajectory of a given load remains the same under the same conditions. What higher mounts do, however, is slightly raise the angle of the bore in relationship to the line of aim.
Let’s say, for instance, that our 7mm-08 has a scope mounted 1-1/2” above the bore. If we sight it in 2” high at 100 yards, a typical 140-grain load will land just about where we aim at 200 yards.
However, if the scope is mounted 2” over the bore, the angle between the bore and the line of aim is increased slightly, because the bore is now ½” further below the reticle. If we sight in 2” high at 100 yards, this extra ½” means that our bullet will land an inch high at 200 yards, instead of right at point of aim. This is because raising the height of the scope ½” at the rifle has the same effect as raising the point of impact ½” at 100 yards.
The bullet will also now land 1-1/2” higher at 300 yards (3 times ½”) and 2 inches higher at 400 yards than it would with a scope mounted only 1-1/2” above the line of bore. This isn’t much but it’s noticeable, and more so with some cartridges. With a load like the 140-grain 7mm-08, with the bullet starting at 2800 fps, it’s about like increasing the muzzle velocity 100 fps. With a faster cartridge, say the 7mm STW shooting the same 140-grain bullet at 3300 fps, an extra half-inch of scope height has the same effect as increasing the muzzle velocity about 200 fps.
Of course we could also raise the height of the 100-yard sight-in ½” and gain the same effect. Or do we? Not really, because with higher mounts the bullet’s trajectory will remain closer to the line of aim, so the risk of shooting over an animal is reduced. This is why I often use fairly high-mounted scopes on varmint rifles.
You learn something new every day. Unless you already know it all...[wink]
White Feather

Yes, since you had "flattens" in quotes in your OP, i was thinking it was more of an "effect" than an actual flattening, which we all know is impossible due to simple physics. [cheers]
 
Damn, WF....looks like your're 0-2 in these shooting basics threads.[thinking]
Did you mean 2-0? I wasn't wrong in either... [grin] You can read I assume. So you see the answer to the scope height vs trajectory. Here is the "bullseye shooters focus on the front sight: explanation:
http://www.bullseyepistol.com/chapter2.htm
I will quote the relevant part:
"1. It is imperative to maintain 'front slight point of focus" throughout the sighting and aiming of the pistol. The shooter must concentrate on maintaining the correct relationship between front and rear sight, and the point of focus must be on the front sight during the short period required to deliver the shot. If the focus is displaced forward, and the target is momentarily in clear focus, the ability of shooter to achieve correct sight alignment is jeopardized for that moment. Frequently, this is the moment that the pistol fires. A controlled, accurate shot is impossible under these conditions."
Op in last nights thread was talking about his shot placement on a target. Bullseye shooters shoot at a target. Glad you know better... [rofl][rofl][rofl]

White Feather
 
Yes, since you had "flattens" in quotes in your OP, i was thinking it was more of an "effect" than an actual flattening, which we all know is impossible due to simple physics. [cheers]

If you plug in numbers in the OPBZ calculator like 2500 fps and .5 bc and just change the scope height from 1 to 5 inches, the two points where the bullet crosses the line of sight get farther apart which means that the round "appears" to shoot flatter and will be on target for a longer distance. Thank you.
y-B-H-BeerToast.gif

White Feather
 
....depending on up or down (sort of how they make range finders for bowhunters shooting down from a stand).

I was commenting on "angle of departure" as it applies when the shotist and the target are at the same elevation, not in high-angle shooting where the shotist and the target are at different elevations where horizontal range to the target differs from the line-of-sight range.

One slight advantage of a higher scope mount is that it flattens trajectory.

IMO, "flattens trajectory" is a poor choice of words in this discussion.

The aforementioned "max point blank" is a better description as is "increases effective range".
 
the two points where the bullet crosses the line of sight get farther apart which means that the round "appears" to shoot flatter and will be on target for a longer distance.

Sorry but this is still a painful statement. You used the word "appears", which pretty much is the same as saying "doesn't actually". So in fact, raising the scope DOESN'T ACTUALLY do anything to the trajectory. What you've done is just raised your viewpoint to a different height so now you'll be lined up at two new distances, once on the way up and once on the way down of the bullet. So while you may have a sight height that makes the bullet perfectly impact at 100 yards and 500 yards at your crosshair, in fact you'd miss by quite a large margin between the two points.

"appears" is the key word. You'd only want such a high setup if you were shooting at KNOWN distances that were always the same, such as between x and y and your targets were pretty big so that they would encompass the rise and fall between those two points. IE, this is kinda non-real world.
 
Sorry but this is still a painful statement. You used the word "appears", which pretty much is the same as saying "doesn't actually". So in fact, raising the scope DOESN'T ACTUALLY do anything to the trajectory. What you've done is just raised your viewpoint to a different height so now you'll be lined up at two new distances, once on the way up and once on the way down of the bullet. So while you may have a sight height that makes the bullet perfectly impact at 100 yards and 500 yards at your crosshair, in fact you'd miss by quite a large margin between the two points.

"appears" is the key word. You'd only want such a high setup if you were shooting at KNOWN distances that were always the same, such as between x and y and your targets were pretty big so that they would encompass the rise and fall between those two points. IE, this is kinda non-real world.

I use the word "appears" because it doesn't change gravity or the velocity of the bullet or its ballistic coefficient. It does allow you to aim at and hit your target along a greater distance. If you are shooting at say a two inch target +/1 one inch, the closest distance and farthest distance at which you can hit the target with a center hold are now farther apart. Silhouette shooters do shoot at known distances. The example using the 7-08 and explaining why varmint shooters do this is real world. Whether it is helpful/useful or not depends on you. I think it is interesting and wanted to share it. Have a great night.
White Feather
 
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