Posted: 8/23/2016 3:40:01 PM EDT
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To level the reticle on my long range rifle I set up a plum line (orange paracord, suspended (pushed outward from supporting fence) by bike U-Lock and weight down by water bottle, across a courtyard in my apartment complex. I used the bike lock and watter bottle to eliminate any variables (building not being level). Distance about 41 yards.
I am confused about the accuracy of my plum line level set up because, while I am easily able to get the vertical line in my reticle aligned with the plum line, and it stays consistent as I adjust the elevation turret. The other features of the building are not aligning with my horizontal reticle. Is this because the building is itself not level? And/or is it due to the fact that the building I set up the plum line on is at about a 45 degree angle from my vantage point? The photos below will provide a better explanation: View from my scope. The orange para cord is the plum line. Its not perfectly aligned because a josseled it when taking the photo, but you can see that the elevation (vertical) reticle crosshair is more than less inline with the plum line. The horizontal lines however do not line up with the cement walkway. 
Here is a photo taken from the vantage point in my apartment, where I am trying the level the scope. If you look carfuly you can see the watter bottle in the bottom of the frame on the left side of the cement column and the bike lock at the top of the frame, straight up. 
Lastly, here is a picture of the courtyard. I set up the plum line parallel to the far cement column. This picture illustrates the angle present from my vantage point and the building supporting the plum line. 
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| I moved the plum line away from the pillar so that its easier to see. but the problem persists, although the vertical cross hair is covering the line, the horizontal crosshair looks like its slightly canted. Is this just an optical illusion due to the orientation of the buildings? Of the building itself not being level? |
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Quoted:
I moved the plum line away from the pillar so that its easier to see. but the problem persists, although the vertical cross hair is covering the line, the horizontal crosshair looks like its slightly canted. Is this just an optical illusion due to the orientation of the buildings? Of the building itself not being level? Use the plumb line. |
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Quoted:
I moved the plum line away from the pillar so that its easier to see. but the problem persists, although the vertical cross hair is covering the line, the horizontal crosshair looks like its slightly canted. Is this just an optical illusion due to the orientation of the buildings? Of the building itself not being level? Gravity won't lie, the illusion will fool you. Once tightened down, set the plumb line up at 50-100 yards. Shoot groups at lowest elev setting and then adjust scope to highest. Keeping the reticle on the cord. Once this is good , now would be the time to add a level of your choice, scope type or receiver. first aligning the reticle to cord. I keep a cheap hardware shook and 550 cord in the range bag |
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Quoted:
Gravity won't lie, the illusion will fool you. Once tightened down, set the plumb line up at 50-100 yards. Shoot groups at lowest elev setting and then adjust scope to highest. Keeping the reticle on the cord. Once this is good , now would be the time to add a level of your choice, scope type or receiver. first aligning the reticle to cord. I keep a cheap hardware shook and 550 cord in the range bag Quoted:
Quoted:
I moved the plum line away from the pillar so that its easier to see. but the problem persists, although the vertical cross hair is covering the line, the horizontal crosshair looks like its slightly canted. Is this just an optical illusion due to the orientation of the buildings? Of the building itself not being level? Gravity won't lie, the illusion will fool you. Once tightened down, set the plumb line up at 50-100 yards. Shoot groups at lowest elev setting and then adjust scope to highest. Keeping the reticle on the cord. Once this is good , now would be the time to add a level of your choice, scope type or receiver. first aligning the reticle to cord. I keep a cheap hardware shook and 550 cord in the range bag Thanks for the input. Next step is trying it out at the range. I have a bubble level on the scope tube (vortex LowPro) and actually one on the rail as well a $10 Amazon special I bought with the intentions of using it to assist in mounting my scope level the the rifle. Turned out to be a major PITA, had to tighten it down a lot to get the level to actually be level, now the screws are threaded and I cant get it off, but it does work OK to indicate when the rifle is level. The Vortex level actually leaves somethings to be desired as well. Its just not that sensitive and the distance between the lines and the bubble is to far apart IMO. I set it up so the right edge of the bubble touches the first line on the right side to indicate that its level, but still the device is simply not that sensitive, sometimes i need to jerk the gun a bit to get the bubble moving... Down the road I would like to upgrade to a Accuracy First Level, apparently these levels register 1 degree of cant (while others will only move with 3-5 degrees of cant- consistent with what I am seeing with my Vortex) and the Accuracy First level takes a Tritium insert with is just plain cool. |
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sit in your room. look at a corner at the spot where the walls meet the ceiling. follow the wall/ceiling joint away from the corner halfway across the room. does it look like it it's going "up" to you? hold your finger 6" in front of your face. now move it 12" from your face. do not freak out!!! your finger isn't shrinking! I promise. go stand in the middle of the street. see how wide it looks where you are, but how small it gets as it goes farther away? dude, the left side of the building is closer to you, so it appears bigger than the right side. |
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Quoted:
sit in your room. look at a corner at the spot where the walls meet the ceiling. follow the wall/ceiling joint away from the corner halfway across the room. does it look like it it's going "up" to you? hold your finger 6" in front of your face. now move it 12" from your face. do not freak out!!! your finger isn't shrinking! I promise. go stand in the middle of the street. see how wide it looks where you are, but how small it gets as it goes farther away? dude, the left side of the building is closer to you, so it appears bigger than the right side. Haha. thanks very much. You should consider being a contributing writer to the "Magic Eye" book series. Its not only the perspective created by the building that had me bothered.... The windage reticle apears canted when is not. I have figured out that this is due to the angle I am looking throught the scope. |
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They are not lining up because of the keystone effect...
Keystone Effect |
| i don't think it's the keystone effect actually, as that seems to be related to images through a lens. while we are looking at an image through a lens, that's not necessary to see the effect he is having. if you just take a carpenter's level and hold it level as if it was the horizontal crosshair, and look at an angle to a building, it will still not line up, even though both the level and the building are level. so the effect is not being caused by distortion in the lens. |