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The Side Mounted Scope on the 6.5mm Carcano


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Have you considered that the scope may have been set for a right-handed shooter who was left-eye dominant?

I've heard this argument raised, but never heard it adequately addressed. [i'm not sure such a person exists...but they may.]

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This is a very strange argument, something similar to selling someone a left handed screwdriver. The scope was mounted on the left side of the Carcano receiver simply because the Carcano bolt stands straight up and down, when being extracted, and the space above the magazine had to be left open to load the six round en bloc clip.There was also nowhere to mount it on the right side without interfering with the bolt. I suppose this mounting may have made it easier for a right handed person who preferred to use his left eye to look through the scope, although this event would have been entirely coincidental.

Edited by Robert Prudhomme
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From the Wikipedia article "John F. Kennedy assassination rifle":

"FBI tests

The FBI tests of the Carcano's accuracy showed:

1)FBI firearms expert Robert A. Frazier testified that "It is a very accurate weapon. The targets we fired show that." From 15 yards (14 m.), all three bullets in a test firing landed approximately 2.5 inches high and 1-inch (25 mm) to the right, in the area about the size of a dime. At 100 yards (91 m.), the test shots landed 2.5 to 5 inches (130 mm) high, within a 3 to 5-inch (130 mm) circle."

Sounds impressive, doesn't it, especially if you do not know that much about shooting.

Straight away, I have no idea what a "3 to 5 inch" circle is, and I'll bet Frazier doesn't, either. Groupings of bullets on a target are usually defined by the diameter of a circle, not an oval, such as Frazier's first reference to a circular group "about the size of a dime". Perhaps Frazier thinks a 5 inch group simply makes the Carcano sound inaccurate. I know that if I had a rifle that shot 5 inch groups or "3 to 5 inch" groups at 100 yards, I would not call it an accurate rifle; rather, I would be taking it to a gunsmith to find out what is wrong with it. A good quality, well maintained bolt action rifle should have no problem putting three shots inside a 1-inch circle at 100 yards. More later regarding what I believe the defect was with the Carcano.

As is obvious by looking at one, a rifle scope is a tube that is mounted above the barrel of a rifle (another tube), usually 1.5-3 inches higher than the barrel. The view through the scope to the target is a straight line, and is called the Line of Sight. As the bullet is affected by gravity as soon as it leaves the muzzle, it cannot follow a straight line to the target but must be delivered in a curving parabolic trajectory that, for most of its journey to the target, is higher than the Line of Sight. This curved path is called the Bullet Trajectory.

As the barrel is lower than the scope and is angled upwards to "lob" the bullet in a parabola to the target, the bullet will cross the Line of Sight shortly after leaving the muzzle of the barrel; usually at a distance of 10-15 yards. If the rifle and scope are zeroed to hit a target at 100 yards, the bullet will cross the line of sight at 10-15 yards, on the ascending leg of the parabola, and cross the line of sight again at 100 yards, on the descending leg of the parabola. In other words, the rifle is accurate at two ranges, 10-15 yards and 100 yards.

With this in mind, let us examine Frazier's claim of the Carcano being 2.5 inches high at 15 yards, and 2.5 to 5 inches high at 100 yards. See anything wrong with these claims? I think they are lies, and I will tell you why.

If 10-15 yards is the range at which the bullet trajectory crosses the line of sight, it goes without saying that a scope should be adjusted to hit a bullseye centre at this range. In fact, this is the range gunsmiths will use to "bore sight" a rifle scope. Watch this excellent brief video about boresighting a rifle.

http://www.youtube.com/watch?v=UgB9J9Bt_Rs

It is clear, after watching this video, that if the Carcano had been placed in this gun vise, the crosshairs of the scope would have been looking 2.5 inches below the bullseye, with the rifle bore lined up on the bullseye. I must point out that a 2.5 inch difference between bore and scope at 15 yards is a VERY large difference. As they say, being a tiny bit out up close equates to being a LOT out far away.

If the bullet hits high at 15 yards, it should be a simple exercise in algebra to determine how high it should hit at 100 yards. Remember, as well, that if the barrel is elevated high enough, the descending leg of the parabola may not begin until well after 100 or 200 yards, giving us almost a straight line from muzzle to where the bullet hits at 100 yards.

15 yards = 540 inches

100 yards = 3600 inches

2.5 is to 540, what "x" is to 3600 or, 3600 x 2.5 over 540 = "x" = 16.67

I do not know if the enormity of what I have shown is apparent to all of you, so I will try to explain. If the rifle shoots 2.5 inches high at 15 yards, the barrel is so drastically elevated, the bullet will land 16.67 inches high of the point of aim at 100 yards, NOT the 2.5 to 5 inches claimed by Frazier.

Frazier (and the FBI) have either told a monstrous lie to the WC, or Frazier was not the expert he claimed to be.

Robert: Regarding the apparent tight spacing of the test shots, have you ever heard of the "Texas Sharpshooter Fallacy"? It's a common mistake made (in logic) when trying to fit certain statistics to a false technical premise. In other words, the shooter is "off target" but - because the shots are closely spaced - still claims to be 'accurate' by circling the scatter. I believe that's what Frazier's comments and the Wikipedia article is attempting to accomplish. -- Gene

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I think Frazier is stretching the truth in a number of places, as well as embellishing it. It sounds very impressive to have three shots hit within the space of a dime, even if it is only 15 yards out. This is not a bad grouping, even for 15 yards, and even if it is high by the incredible amount of 2.5 inches. The one inch lateral deviation to the right at 15 yards is about what one would expect from a side mounted scope, as that is roughly how far apart scope and barrel are. However, one would expect line of sight and line of departure, with a side mounted scope, to be on a converging lateral course and be meeting at the 100 yard mark. Why, then, does this rifle have a lateral spread of 5 inches on the target at 100 yards?

The answer is quite simple, actually. There is no question that the phenomenon, witnessed by Frazier, of the bullets landing progressively further to the right of the bullseye at 100 yards, making a 5 inch lateral spread on the target, was also occurring on the 15 yard target, despite all of the 15 yard bullet holes landing within the space of a dime. Frazier wrongly attributed this "walking away" from the bullseye to the scope needing to "settle in" following adjustments made to it but, this is utter nonsense. The real reason was that the end of the wooden forestock was warped from improper storage and maintenance of the rifle. The forestock was pressing against the barrel, bending it slightly and causing the shots to go wide. With each shot, the barrel heated and expanded, causing the forestock to push on the barrel with increasing pressure and making the shots land even further to the right, eventually resulting in a 5 inch spread at 100 yards.

How, then, could all the shots land within the space of a dime at 15 yards? Once again, we must use algebra. Assuming a dime to be 3/4 inch in diameter, we can say the following:

.75 is to 15 what "x" is to 100

.75 x 100 divided by 15 = x

75/15 =x

x = 5 inches

In other words, the "walking away" of the bullets, seen as a 5 inch lateral spread at 100 yards, still takes place at 15 yards but manifests itself as only a 3/4 inch lateral spread.

Edited by Robert Prudhomme
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I think Frazier is stretching the truth in a number of places, as well as embellishing it. It sounds very impressive to have three shots hit within the space of a dime, even if it is only 15 yards out. This is not a bad grouping, even for 15 yards, and even if it is high by the incredible amount of 2.5 inches. The one inch lateral deviation to the right at 15 yards is about what one would expect from a side mounted scope, as that is roughly how far apart scope and barrel are. However, one would expect line of sight and line of departure, with a side mounted scope, to be on a converging lateral course and be meeting at the 100 yard mark. Why, then, does this rifle have a lateral spread of 5 inches on the target at 100 yards?

The answer is quite simple, actually. There is no question that the phenomenon, witnessed by Frazier, of the bullets landing progressively further to the right of the bullseye at 100 yards, making a 5 inch lateral spread on the target, was also occurring on the 15 yard target, despite all of the 15 yard bullet holes landing within the space of a dime. Frazier wrongly attributed this "walking away" from the bullseye to the scope needing to "settle in" following adjustments made to it but, this is utter nonsense. The real reason was that the end of the wooden forestock was warped from improper storage and maintenance of the rifle. The forestock was pressing against the barrel, bending it slightly and causing the shots to go wide. With each shot, the barrel heated and expanded, causing the forestock to push on the barrel with increasing pressure and making the shots land even further to the right, eventually resulting in a 5 inch spread at 100 yards.

How, then, could all the shots land within the space of a dime at 15 yards? Once again, we must use algebra. Assuming a dime to be 3/4 inch in diameter, we can say the following:

.75 is to 15 what "x" is to 100

.75 x 100 divided by 15 = x

75/15 =x

x = 5 inches

In other words, the "walking away" of the bullets, seen as a 5 inch lateral spread at 100 yards, still takes place at 15 yards but manifests itself as only a 3/4 inch lateral spread.

The Texas sharpshooter is a fabled marksman who fires his gun randomly at the side of a barn, then paints a bullseye around the spot where the most bullet holes cluster. The story of this Lone Star state shooter has given its name to a fallacy apparently first described in the field of epidemiology, which studies how cases of disease cluster in a population.

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We need to remember that countless deer hunters have put side mounted scopes on their top ejecting Winchester lever actions with great success when hunting deer.. This yr my 7 kids gave me a sporterized 1917 Enfield in.30-06 for Fathers Day. I put a side mounted scope mount on so I could use stripper clips to reload. The scope is a 1.5X4 power modestly priced scope. I was dead on at 100yards with three shot

The problem here is quality of the scope and mount not that it was side mounted. I have shot a MC and as a former police sniper I can tell you it absolute trash. In the hands of a mediocre shot it's more likely he would have shot Jackie or Clint Hill.

Edited by Evan Marshall
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Have you considered that the scope may have been set for a right-handed shooter who was left-eye dominant?

I've heard this argument raised, but never heard it adequately addressed. [i'm not sure such a person exists...but they may.]

I am right handed, left eye dominant with an uncorrectable astigmatism on my right cornea (making my sight from my right eye the equivalent of 20/40) my left eye is 20/20. The left eye, being dominant is used, more than the right. It has not affected my ability to sight a rifle or any other weapon, in fact, anyone that knows me for a long time would tell you I'm a deadly accurate shooter. The shooting where the condition is thought to matter most is hunting with a shotgun or trap and skeet where a lot of shooters keep both eyes open. Because I grew up shooting, I may have learned to unconsciously compensate but it's never been an issue as far as I can remember.

If I cover my left eye with my hand my vision feels slightly impaired to me, whereas if I cover the right, other than the loss of peripheral vision, it doesn't feel as unnatural to me.

Hope that clarify's the issue somewhat.

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Hi Chris

I began wondering where the theory of the scope being mounted on the Carcano for a left handed person, or a right handed, left eye dominant person, actually got its beginnings. For some strange reason I seem to recall it was one of the FBI agents that told this to the WC. Any ideas?

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Robert,

I had heard that theory before as well, but I don't remember where, (and I think I had discounted it because of my own experience), I'll try to track it down.

As far as what affect it would have on the sight - I don't know - but I would tend to think it would be minuscule. By habit, when using a scope I usually try both eyes and go with whatever feels natural. With iron sights I usually start with the left eye and if my nose is in the way, (like it is on the M16), I go with my right. I suppose there might be some small parallax affect if a left eye dominant shooter zeroed with his left eye and then a right eyed shooter picked up the weapon. In my tank days, the headrest for the gunner's primary sight was switchable for a right-eyed or left-eyed gunners and almost always was set on the right except on my tank - making many a "WTF" when other gunner's sat in my seat. :)

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I've been trying to locate where it was that I saw it was an FBI expert who explained the left mounted scope being for a right handed/left eye dominant shooter but I've had no luck. It is really bothering me, though, because the more I think about it, the more I am convinced it was one of the FBI "experts" who stated this.

Anyone have any recollections on this?

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Found it. CE 2560 is a record of a telephone conversation between the WC's Eisenberg and a Mr. Warner at the Aberdeen Proving grounds, in which the mounting of corrective shims on the base for the Carcano scope was discussed. To quote CE 2560:

"The gunsmith observed that the scope as we received it was installed as if for a left handed man."

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