SIGHT ALIGNMENT and "blindeye"

[joeb33050]

I solicited comments on the ASSRA and Cast Boolits forums, and while there were plenty of comments, only “blindeye” on the ASSRA forum commented that the manual is wrong. I moved the “SCOPE” and “METALLIC SIGHT” headings on the drawing for my query, they’re shown as in the manual, below.

TC 23-14, Sniper Training and Employment, dated October 1969, replaced by
FM 23-10 Sniper Training, dated 17 August, 1994
See figure 3-17
“SCOPE” and “METALLIC SIGHT” are in the wrong places.


It looks to me that both the Metallic Sight and Scope pictures are wrong.
For the Metallic Sight
See the bottom right picture. With the rear peep centered on the front blade, and the blade just under the bullseye, the bullet hits on top of the front blade, the sights are set correctly.
See the top left picture. The blade, we assume, is directly under the bullseye. The rear peep has been moved to the right. The bullet is shown moved left. Not true. If the rear peep sight is moved right, the bullet impact point moves right. Impact point moves the direction the rear sight moves.
Top middle is wrong, rear peep moved left, impact point moves left, not right as shown.
Top right is wrong, rear peep moved down, impact point moves down, not up as shown.
Bottom left is wrong, rear peep moved up, impact point moves up, not down as shown.
We’re told that the eye centers in the rear peep automatically, and it seems to be true because of the precision with we can shoot iron peep sighted guns. I suppose that one can hold the peep off of center, but I’ve tried it and it ain’t easy. Conscious effort is required.
For the Scope
I used a B&L Balvar 6-24, a Lyman 30X STS, and a Prairie Master 8-32. Set each on a solid rest, sighted on a radio tower a long way away, adjusted out the parallax. Then moved my head/eye to get the crescents shown on the drawing. With any scope at any power, the crosshairs did not move as the eye moved. Tried again looking at a car ~ 200 yards away. Again, the crosshairs did not move as the crescents showed up.
The drawing just isn’t true.
The Lyman STS 30X and Balvar 6-24; and a lot of other scopes, have the upper limit of parallax adjustment ~200 yards. This means that from ~ 200 yards to infinity the parallax setting is ~ the same, very close to the same. I would guess that snipers shoot at 200 yards and over, so the parallax setting should be 200 yards/infinity and not changed unless a target way closer than 200 yards must be looked at. If the target is a lot closer than 200 yards, we’re out of the sniping business. What I think this means is that the sniper should have parallax set at 200 yards/infinity, and use metallic sights if the target is a lot closer than 200 yards where parallax becomes a problem.
If I’m right and the manual is wrong, maybe Larry Gibson can let the Army know.

[bullshot]

Joe
I have not read any of the manuals you refer to, however if I were to just look at the examples of the iron sight diagrams, assuming the lower right is sighted in as shown, then all the rest are absolutely correct. The diagrams don't show the target. Assuming the target is in the same place in all the diagrams then the shots would be as shown.
As far as the scope diagrams I can't comment. I have shot a lot of rifles that didn't fit me as far as eye relief is concerned and I shot groups just fine,I'm sure I try to keep the field of view centered if it not full.. If there is no parallax, shots should be constant, with a proven load . Eliminating human error and external conditions(wind, light , mirage, any stresses on the position etc). FWIW

[44man]

All are correct!
With a scope that is set parallax free at one range, the slight crescent has little effect but most fixed, low power scopes are set at 100 yd's. That means at all other distances, not looking down the exact center of the scope will move the POI.
Blindeye is thinking about rear sight adjustment and not where the barrel is pointing.

[joeb33050]

Joe
I have not read any of the manuals you refer to, however if I were to just look at the examples of the iron sight diagrams, assuming the lower right is sighted in as shown, then all the rest are absolutely correct. The diagrams don't show the target. Assuming the target is in the same place in all the diagrams then the shots would be as shown.

See bottom right, metallic. When the sights are aligned, the bullet hits just on top of the post. The gun is sighted in. Now look at bottom left. EITHER the front blade has been moved down, OR the rear peep has moved up. The bullet moves the way the rear sight moves, opposite the way the front sight moves. If the rear moved UP, the bullet moves UP. If the front moved DOWN, the bullet moves UP.
Think about it.



As far as the scope diagrams I can't comment. I have shot a lot of rifles that didn't fit me as far as eye relief is concerned and I shot groups just fine,I'm sure I try to keep the field of view centered if it not full.. If there is no parallax, shots should be constant, with a proven load . Eliminating human error and external conditions(wind, light , mirage, any stresses on the position etc). FWIW
Hard to understand, but why?

[joeb33050]

All are correct!
With a scope that is set parallax free at one range, the slight crescent has little effect but most fixed, low power scopes are set at 100 yd's. That means at all other distances, not looking down the exact center of the scope will move the POI.
Blindeye is thinking about rear sight adjustment and not where the barrel is pointing.
They're both wrong. Parallax has nothing to do with it. Snipers should have scope parallax set at 200 yards/infinity.
Think about it.
Where's Felix????
joe b.

[felix]

What is the question, Joe? Parallex comes into play whenever focusing comes into play between three objects,
and in our case lining up the target, crosshairs, and eyeball as a composite. Parallex adjustment takes out the variation in focus between the target and crosshairs, so that the eyeball can move freely. If you only have two objects in question, like in a camera, parallex does not come into play. If you have four planes, then two parallex adjustments would be required for the same effect. ... felix

[KYCaster]

JoeB sez, "See bottom right, metallic. When the sights are aligned, the bullet hits just on top of the post. The gun is sighted in. Now look at bottom left. EITHER the front blade has been moved down, OR the rear peep has moved up. The bullet moves the way the rear sight moves, opposite the way the front sight moves. If the rear moved UP, the bullet moves UP. If the front moved DOWN, the bullet moves UP.
Think about it."


Well Joe, that's true when you move the sights in relation to the bore, but that's not the case here.

The sights remain in the same relationship to the bore, you're just pushing the front sight (and the muzzle along with it) out of alignment with the rear sight, so the bullet's impact will move in the direction you move the muzzle.

Jerry

[montana_charlie]

It looks to me that both the Metallic Sight and Scope pictures are wrong.
For the Metallic Sight
See the bottom right picture. With the rear peep centered on the front blade, and the blade just under the bullseye, the bullet hits on top of the front blade, the sights are set correctly.
See the top left picture. The blade, we assume, is directly under the bullseye. The rear peep has been moved to the right. The bullet is shown moved left. Not true. If the rear peep sight is moved right, the bullet impact point moves right. Impact point moves the direction the rear sight moves.
Top middle is wrong, rear peep moved left, impact point moves left, not right as shown.
The metalic sight illustrations are correct.

Moving a rear sight to the right will cause a bullet to strike to the right...only if the front sight is also pulled to the right to align with the newly positioned rear.

If a rifle is correctly aligned with a target and the buttstock is pushed to the right to produce the top left drawing, that will throw the bullet to the left of the target, as indicated. Similarly, if the same (correctly aligned) rifle had the front post pulled to the left to produce the top left picture, the bullet would still impact to the left.

CM

[joeb33050]

JoeB sez, "See bottom right, metallic. When the sights are aligned, the bullet hits just on top of the post. The gun is sighted in. Now look at bottom left. EITHER the front blade has been moved down, OR the rear peep has moved up. The bullet moves the way the rear sight moves, opposite the way the front sight moves. If the rear moved UP, the bullet moves UP. If the front moved DOWN, the bullet moves UP.
Think about it."


Well Joe, that's true when you move the sights in relation to the bore, but that's not the case here.

The sights remain in the same relationship to the bore, you're just pushing the front sight (and the muzzle along with it) out of alignment with the rear sight, so the bullet's impact will move in the direction you move the muzzle.

Jerry
Well, Jerry, you're right and the manual is right on the metallic sights. Your post was my epiphany.
I came here to find out if I was wrong, and I was.
Thanks;
joe b.

[joeb33050]

What is the question, Joe? Parallex comes into play whenever focusing comes into play between three objects,
and in our case lining up the target, crosshairs, and eyeball as a composite. Parallex adjustment takes out the variation in focus between the target and crosshairs, so that the eyeball can move freely. If you only have two objects in question, like in a camera, parallex does not come into play. If you have four planes, then two parallex adjustments would be required for the same effect. ... felix

Felix;
The question is:"With a parallax adjusted scope, when the eye moves to give the crescents shown on the drawing, do the crosshairs move=bullet impact point moves." My testing says not.
joe b.

[44man]

They're both wrong. Parallax has nothing to do with it. Snipers should have scope parallax set at 200 yards/infinity.
Think about it.
Where's Felix????
joe b.
Sniper, target and varmint scopes have parallax adjustments while most fixed power hunting scopes are set at the factory to be parallax free at 100. Even some handgun scopes are set at 100 which makes it critical to look down the center at closer ranges.
The old Weaver fixed power scopes were nice in that the turret could be loosened and slid back and forth to adjust parallax at a closer range for a .22.
When set parallax free at the range shot, cross hairs will not move if you move your head. All the adjustment does is bring the focal plane of the target to the same plane of the cross hairs instead of in front or behind them.