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Old April 12, 2019, 10:44 AM   #26
Pahoo
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Sorry bout that !!!

Quote:
how do you know if the level is level?
Verify with a Plumb-Line. !!!!

Be Safe !!!
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Old April 13, 2019, 02:40 PM   #27
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There are different methods. Hdbiker offers a reality check approach that is good. I set guns up with the sights mechanically straight first, then try snap shooting at some dryfire targets to double-check that the particular gun doesn't mount funny for me, but mechanically straight usually works for me.

The way I set mechanical straightness is with a nifty little tool that NECO sells. It is a V on the end of a plate with a vertically adjustable V with a bubble level vial on it. The lower V centers on the barrel under the scope bell. The upper V is then adjusted until it is centering on the scope bell simultaneously. The vial is then indicating level when the scope is straight up over the barrel with respect to gravity. It would not work on an offset scope, but for most rifles, it is just dandy.

The way I use it is I clamp the gun in a vice with leveling feet. I put that gadget on and adjust the feet until the bubble is centered. At that point, the gun is mechanically upright. This works regardless of whether the gun has a convenient flat spot on the receiver or not. I remove the level and loosen the scope screws and use a self-leveling laser line (indoors) or a plump line (outdoors; this is what fluorescent orange plumb line is for) to adjust the reticule position. I then alternate tightening front and back on one diagonal with doing it on the other diagonal and checking the reticule position until the rings are tight and the reticule is still aligned with the plumb line. At this point, if I'm going to put a cant level on the scope, I recheck that the gun is still level and put it on and make sure it both levels agree as to where level is.
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Old April 13, 2019, 02:47 PM   #28
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I eyeball it.
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Old April 13, 2019, 04:40 PM   #29
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A little different than some of the above but I'm doing this on a
1) Get the rifle boresighted at 200 yards with a known plumb in a mount.
2) Level left / right using a ... level (no surprise) in the mount.
2) Mount the (lapped) scope rings.
3) Mount the scope in the rings.
4) Zero the scope on the laser dot
5) Rotate the scope until the reticle is zeroed.
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Old April 14, 2019, 01:02 AM   #30
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How do you know if the level is level?

Well, it's not called an unlevel.
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Old April 14, 2019, 04:32 AM   #31
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All this begs the question. Why do we need to level the scope? A unleveled scope leads to a canted rifle. Then what's wrong with a canted rifle?

Furthermore, all that level and plumb line only ensures the proper setting of the rifle BEFORE the shot is fired. How do we know it is still proper after the trigger is pulled?

Perhaps the ultimate check is what's on the target paper?

-TL

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Old April 14, 2019, 05:22 AM   #32
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Quote:
Originally Posted by tangolima View Post
All this begs the question. Why do we need to level the scope? . . . .
This is exactly what I was wondering. Why level the scope? As long as it's been properly sighted in, does it matter if it was leveled? I've heard of leveling the scope before but do not understand the reason.
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Old April 14, 2019, 08:40 AM   #33
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A level scope allows you to adjust POI vertically using the elv knobs and lets the bullet track along the vert line of the reticle.

If the scope is out of level, as you put elevation into the knobs the bullet also get windage adj
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Old April 14, 2019, 12:11 PM   #34
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Bingo !!!

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A level scope allows you to adjust POI vertically using the elv knobs and lets the bullet track along the vert line of the reticle.
Sharkbite
Great reply and right on the money. Gravity is always at work !!! ….

Thanks and;
Be Safe !!!
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Old April 14, 2019, 12:28 PM   #35
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That's correct. If the vertical line of the scope is canted, you then have to dial in some windage as well as elevation to maintain zero as you shift sight settings for longer ranges. If you have a mil-dot scope or another scope with range lines on them, they will be off to the side if there is any cant, and not directly usable.

In general, because most rifles have their bore lines above the center of support for the stock on the shooter's shoulder, the main vertical recoil moment, which affects POI, will be straight up and needs to be co-linear with the vertical reticule hair as well as aligned with the direction of gravitational pull to keep vertical sight adjustments strictly vertical and not contribute to the windage setting. This is why long range shooters put cant levels on their guns. It tells them when they have all those elements aligned at once.

You could also choose to intentionally put a slight cant in the direction of your rifling twist to compensate for wind drift. The old Springfield '03 ladder sights have that cant built in and a scope can make use of it too.

As with much to do with precision shooting at longer ranges, this isn't an issue for someone hunting medium and larger game in places where the shots are never over 200 yards. Where it bites you hard is shooting at ranges long enough for the bullet to be falling faster than flat shooting helps to overcome and where range correction has to be made. Beyond 300-350 yards would be typical numbers for most medium to high power rifles.
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Old April 14, 2019, 11:18 PM   #36
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My thought exactly. We always assume the barrel flips up always the stock's center line. But it is not necessarily always so. It depends on how the rifle is held, the shape of the shooter's shoulder, and some other things. The level / plumb line rituals just get it close. But live fire is the only final check.

I would crank the elevation up and down, firing groups at different settings, while trying hard to hold the gun consistently. If the windage significantly changes with elevation, I would rotate the scope slightly to compensate.

Another rhetorical question. If the group drifts to the left with increased elevation, should I rotate the scope clockwise or counter-clockwise?

-TL

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Old April 15, 2019, 05:31 AM   #37
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Thank you all for the explanation. Long-range shooting is pretty much PFM (Pretty Freakin' Magical) for me. I do notunderstand its intricacies. It seems to me that having the scope "out of rotation" (for lack of a better term, where the vertical crosshair is not quite vertical) might require adding in some windage adjustment to let the bullet track the vertical, but when I hear "level," I'm thinking front-to-back. It may well be that my understanding is deficient, but I don't quite get how having the front higher than the back, or vice versa, would affect the bullet's ability to track that vertical crosshair. Or am I misunderstanding how you're leveling? Are we talking about leveling front-to-back, or left-to-right? I get that "both" is probably the answer, but I'm trying to pin down which one is a problem.
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Old April 15, 2019, 10:10 AM   #38
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Spats, leveling as we are talking about refers to the rifle tilted to the right or left or the scope is "out of rotation" to use your words. Basically you need the crosshairs to point perfectly up and down and perfectly level to the right or left in order to keep the bullet from going to the right or left when you start dialing in elevation.

For your other comment about the scope being level front to back, this isn't really a thing. You can buy scope mounts that purposefully puts the objective lens (closest to the muzzle) lower. Most common example is a 20 MOA base. Basically what happens with a normal scope mount is that the scope runs out of adjustment to account for the extreme drop of the bullet at longer distance. The 20 MOA base right off the bat means you can get your crosshairs to aim 20 MOA lower. Or looked at another way, the 20 MOA base allows you to zero your rifle at 100 yards about 80 clicks closer to the top of it's adjustment range (assuming 1/4" per click @100 yards). As you get out to the really long distances, you have 80 more clicks of elevation you can dial in. Hope that makes sense.

I remember when long range shooting seemed almost magical to me. The crazy part is it's no where near as hard as I thought it would be. The exact same principles that helped me shoot small groups at 100 yards is the majority of shooting long distance (I'll caveat within 1000 yards). The hardware you're shooting likely has to be upgraded, but other than that it's mainly some math, learning to read ballistic tables and the wind. My uncle is responsible for this expensive past time of mine, and I really didn't believe him when he told me the problem was more my equipment than me. He was right! Of course this was in the days before The surprising level of accuracy you can get from guns like the Ruger American for cheap (I wasn't familiar with Savage back then.. I wish I had learned about them sooner). Now, even more so, reasonable accuracy at distance is very attainable with most budgets. And I say "reasonable" on purpose. Chasing smaller and smaller groups such as is required for competition shooting is a never-ending black hole of tweaking, testing and buying new reloading equipment. I can tell my desire for small groups is only so strong! Haha

There's something addictive about hearing that "gong" at 600+ yards. And imagine the confidence you have with a 300 yard shot on an animal when you can hit 600 yards 4 out of 5 times. I love long range shooting and hate that the closest 600 yard range is about 3 hours away from me. I've got 100 yards 30 minutes away and 200 yards an hour away. When I can find time to shoot, I normally go to the 200 yard range.

Last edited by ndking1126; April 15, 2019 at 10:27 AM.
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Old April 22, 2019, 07:50 PM   #39
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You need to level rifle AND scope.

Just look thru the scope at the bottom of the scope.
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Old April 23, 2019, 12:42 AM   #40
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This is the method I've used. I typically use a level on the elevation turret to get me close, and finish with the method in the link.

https://www.thefirearmblog.com/blog/...scope-reticle/
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Old April 23, 2019, 05:46 AM   #41
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Quote:
Originally Posted by ndking1126 View Post
Spats, leveling as we are talking about refers to the rifle tilted to the right or left or the scope is "out of rotation" to use your words. Basically you need the crosshairs to point perfectly up and down and perfectly level to the right or left in order to keep the bullet from going to the right or left when you start dialing in elevation. . . . . For your other comment about the scope being level front to back, this isn't really a thing. . . . .
Thank you, and thanks to everyone who responded to my questions. Now it makes sense.
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Old May 12, 2019, 11:49 AM   #42
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Is leveling the scope a process that ends up with the LOF (bore axis) tracking the vertical reticle wire as the scope elevation is moved from stop to stop?
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Old May 12, 2019, 03:40 PM   #43
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Yes ??

Quote:
Is leveling the scope a process that ends up with the LOF (bore axis) tracking the vertical reticle wire as the scope elevation is moved from stop to stop?
Well, the way I am understanding your question, I have to say; YES. ….

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Old May 12, 2019, 09:23 PM   #44
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Originally Posted by Pahoo View Post
Well, the way I am understanding your question, I have to say; YES. ….

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That can be done at home without shooting bullets.
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Old May 13, 2019, 10:12 AM   #45
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Another useful thing to have is a setup for zeroing your scope adjustments before you set the scope up on the gun. You may be able to do this by counting clicks to find the middle of the ranges of elevation and windage, but with some scopes the adjustment to optical center that way may not be exact. Stoney Point used to sell molded plastic v-blocks for optically zeroing scope adjustments and anyone with a 3D printer could make you a set, but I have just used 1/4" round head Nylon screws set into scrap wood as shown in the old illustration below. A change I made since was to notch the vertical wood between the screws so I could set them a little further apart for more stable scope support and I hot-melt glued the screws in to keep the screwdriver slots parallel to the scope.



The idea with that fixture is to tweak the scope adjustment knobs until rotating the scope no longer moves the center of the crosshairs off whatever you are looking at through the scope. Once you have that optical zero, you set the scope up on the gun as I described in post 27 or by other means of your choosing to get the vertical crosshair on a line that passes through the bore center. Once you have done that and you know the height of the scope above the bore line and assuming your base and rings don't introduce any left or right direction error, you will be able to dial in a zero as good as any bore sighter can produce. In other words, a zero you have only to correct for barrel vibration and recoil moment effects on POI.

If you have a long-range scope base with elevation, don't forget to subtract that number from your elevation setting to determine what your initial zero settings should be.

For example, I find the optical rotation center for my scope as above. I mount it with a base and ring set that puts the center of the scope 1.5 inches above my bore line. I have ammunition that will fire the 155 grain Sierra 2156 Palma MK from the gun at 3000 fps. The base has +20 MOA of elevation built in for long range. I decide to find the 100-yard zero first. So I put my load specifics into the simplified trajectory calculator at the JBM ballistics site. On that software I will do two things that may seem a little odd:
  • Enter the zero range as 1 yard.
  • Enter the scope height as zero.

Also, I
  • Set the range and range increment for the zero range I want.
  • Also, I set wind and target speed to zero.

The result will show a drop of -2 inches or 1.9 MOA at 100 yards. Since my scope height is 1.5 inches, the actual drop will be another -1.5 inches below my scope line of sight. So, for adjustment purposes, the drop is -2 inches plus -1.5 inches or -3.5 inches. At 100 yards, an inch is close enough to an MOA so I can use +3.5 MOA as the expected correction. I subtract the scope base elevation from that number to get the adjustment correction. That is,

+3.5 MOA - 20 MOA = -16.5 MOA,

so turn I turn the elevation knob down -16.5 MOA to get my trial zero at 100 yards.

If you want to correct to mathematically exact MOA just because you can, multiply pi times the actual range in yards and then divide the result by 300 yards to get the conversion factor. Divide the scope height by that conversion factor (1.0472 at 100 yards). For 1.5 inches that gives 1.43 MOA. Add 1.43 MOA to the 1.9 MOA from the table to get 3.33 MOA adjustment correction. In my case, I would subtract 20 MOA from that number and get -16.67 MOA sight adjustment to produce my trial zero.

Note that the error from using inches as MOA instead of mathematically exact MOA is just 0.167 MOA in this example. In reality, barrel vibration and the action of recoil moments on my hold will introduce more error than that, and I will have to dial in their correction by actual firing and record it. So there is no point in being tighter than using inches as MOA at 100 yards, IMHO. If you have 1/8 MOA clicks or 1/10 MOA clicks on your scope, you can dial in closer to correcting that small error. But I have to say from experience with a 1/8 MOA mil-dot scope that the time it takes to count all those clicks and the increased likelihood of losing count of a large number of clicks is something I found made such fine adjustments more a nuisance than a help. The standard 1/4 MOA adjustment is already finer than most people can hold in most real conditions what with wind moving around and so on. Mid Tompkins told a class I took that he doesn't want sight adjustments finer than 1/2 MOA for long-range because the wind usually changes more than 1/4 MOA in the time it takes to add a click to the adjustment. He said our scores would be higher if we learned to correct errors that small by holding off slightly.
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Old May 13, 2019, 10:21 AM   #46
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True

Quote:
That can be done at home without shooting bullets.
This is true and confirmed in the field. If you already knew that, why did you ask ??? …

Be Safe !!!
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Old May 13, 2019, 10:31 AM   #47
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He was just confirming how the word "level" was being used in this context, not suggesting he didn't know how to make it happen.
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Old May 13, 2019, 10:58 AM   #48
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I missed that

Quote:
He was just confirming how the word "level" was being used
Did not catch that and my apologies.

Bart B., probably knows more about shooting than I do. …..

Be Safe !!!
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Old May 13, 2019, 11:14 AM   #49
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Originally Posted by Unclenick View Post
Another useful thing to have is a setup for zeroing your scope adjustments before you set the scope up on the gun. You may be able to do this by counting clicks to find the middle of the ranges of elevation and windage, but with some scopes the adjustment to optical center that way may not be exact.
All the scopes I've put the erector tube lenses on scope optical (outer tube) center had more clicks up and right, towards the knobs, to their mechanical limits. And the reticle/LOS stopped moving several clicks before the limit. Proof to me the erector tube was against the outer tube or something else.

Nobody in the shooting sports used the trig MOA value until the hand held scientific calculators came out in the 1960's.

Metallic sights can be spaced to whatever value you want. The original standard for match aperture rear sight was 40 TPI lead screws, 12 clicks per turn, 30 inch sight radius. Externally adjusted target scope mounts had a 7.200 inch spacing, 40 TPI lead screws. .0005" per click.

Very few, if any, internally adjusted scopes are exact to published click values. Their lenses have a few percent tolerance in focal lengths.

Exact trig value below was calculated to 102 decimal places for those wanting more precision:

1.04719753642832854694747069666400334739860873986429
830552235157457471965151538005004775737357536725837... inches per 100 yards...
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