Is a scope level needed?

[Pdvdh]

Michael,
I don't ever use the Cant feature in ColdBore 1.0, because I don't ever mount scopes and scope levels to shoot with a canted rifle. The zero range setting in ColdBore 1.0 is definitely altering the horizontal POI values for cant. Dunno what's up with that. I'll read the manual and see if I can sort it out.

Going to delete my tables for the time being, and research the ColdBore 1.0 Users Manual. See if there's an explanation on rifle cant calculations.

 

[Michael Eichele]

Not sure where the mistake is but there will be more than 9.22" of error at a grand. Try setting the 'zero range' to 1000 yards. Or 1250 for that matter. Some ballistic calculation engines aren't written properly and they don't reflect cant values properly unless you set the zero to the range you're trying to analyze. It should be around 37" or so.

 

[Pdvdh]

Thanks for pointing that out. I need to spend some time researching my ColdBore 1.0 Users Manual.

 

[Dgd6mm]

I believe you should use one for any type of shooting. It will tighten your long-range groups and also help at shorter ranges. 13 pages, I hope the OP is keeping up with his thread.

 

[Deleted member 46119]

How many of you guys use an anti-cant level while shooting/hunting? For those that do, is this something you use all of the time? Over 1000/ under 1000? Just curious to see what you guys do.
1hornhunter

To get back to the OP.

An anti-can't device is not required, like all, it is a tool.

but

With cant, having the scope and rifle in a known plane shot to shot, is going to be better for making the same POI. Physics is physics, ballistics is ballistics. It's really not logical to argue with it.

now

Having the sighting device and bore in the same vertical plane. Well, there can be discussion of the pros and cons of setups for specific purposes. Quoting D. Tubb's setup for a specific purpose as a comparison for a different purpose is as sensible as arguing the specific gravity of a gold molecule. You can argue all you want but it ain't gonna change things.

For general and hunting use, having the sighting device and bore in the same vertical plane, is "best" any changes in distance are not going to compound in a left or right compensation requirement.

To proof your cant ability or device setup and vertical, draw an inverted "t" on a large blank piece of paper for a 100 yard target. Put your best 3 shot group on the cross. Then dial in 8 MOA and using the same POA (point of aim), shoot the best 3 shot you can again. Measure the distance from the center vertical line. If it drifts left or right, your cant is off and your shots while hunting will drift left or right, so your cant ability or device needs work. Physics is physics, ballistics is ballistics. You can argue all you want but the technique will prove your consistency in controlling cant and your sighting device setup.

Repeat at 200 and 300 yards. If you got your cant control down either by your own eye or by your device, your horizontal deviation will never vary.

BTW: I have an astigmatism that rotates my understanding of vertical and horizontal lines to the left. I use multiple levels on the action and scope for setup. I prefer my anti can't devices mounted to the scope and try very hard not to move them once they are correct.

When shooting open sights I have to use corrective lenses and keep my head in the same place in relation to the sights vertical and horizontal plane. Canting my head differently but keeping the rifle in the same physical plane will change my perception of the sights and point of aim.

I hope this helps.

 

[Unofficial Gun Addict (UGA)]

I did not know I had a problem until I installed an anti-cant level.

Ok... Went to the range tonight... And it was 100% pitch black... No moon... And I shined a light on my targets. I have to admit... Without any point of reference other than my targets, it was definitely hit or miss when I checked my cant. when I really believed I was true... Sometimes I wasn't.

So... I have to thank all of you for this thread and your persistence that a level is a cheap good thing to have on ones scope... And that it is harder to determine cant even if you believe you can. Without the surrounding environment to help me determine level... I was indeed, titling left every other shot... and level the others. Most of the time when I was off... The bubble was split by the right line... But there were a couple of times the bubble was totally right.

I honestly believe that I was staying level half the time due to muscle memory from looking at the level and trueing up my scope from the previous shot, so I have a feeling that without the level... I'd have been off pretty consistently left (bubble right).

So I agree with Secondranch 100%. Didn't realize I had a problem until I got a level, and I wouldn't have gotten a level without the overwhelming response in this thread that it is needed for long distance shooting.

Thanks all!

-James

 

[JRu]

If David Tubbs set a hunting rifle up with the gun at a 7* cant with a scope that was mounted 1.75" above the bore. The bore would only be offset from the scope about .21". So if the windage was zeroed in at 100 yards you would have a windage error of .21" at 200, .84" at 500, and 1.89" at 1000 yards. If you zero your windage at a further distance like 400 yards, your windage error would be: .105" at 200, 0.0" at 400, .105" again at 600, and only .315" at 1000 yards.

So in my opinion if you are willing to zero your windage at a further distance like 400 or 500 yards, and are not excessively canting the rifle, bore to scope alignment really is not a significant factor. Even if you zero in at 200 yards like most of us do, you have less than an inch of windage error at 1000 yards with this example.

Exactly. People are mixing two issues which creates confusion. Canting the scope when shooting creates the angular error, which is significant. Not having the scope vertical centerline axis intersect the bore is just linear offset and the error will be a multiple of the sight-in distance.



With regular (non offset) scope mounts you can only end up with situation B when mounting the scope (within tolerances of action and mount of course, but let's consider that insignificant for the purpose of this exercise). But by canting the rifle to level the crosshair when shooting, you convert situation B into situation C, and your bore offset induces only a linear error, not angular.



As seen from above, when the crosshair is level, but bore is offset. The erector tube points at the sight-in point and any offset is a multiple of that sight-in distance.

You need to have the crosshair level WHEN SHOOTING. Everybody agrees on that. But the bore offset? Well it has to be pretty severe to produce measurable results. I can definitely eyeball the offset to less than .1" when mounting the scope. I zero at 165 yards (150 meters). That means at most 1" at 1815 yards, IF the crosshair is level when firing the rifle.

 

[Tnwhip]

And another thing. Wouldn't the bubble be more accurate mounted on top of the scope. The farther away from the bore the more sensitive to can't. How much difference would it be mounting the bubble on top of the scope or the rail?

 

[7magcreedmoor]

And another thing. Wouldn't the bubble be more accurate mounted on top of the scope. The farther away from the bore the more sensitive to can't. How much difference would it be mounting the bubble on top of the scope or the rail?

I don't know that it would affect the accuracy at all (and I don't miss any more this way- nor miss any less HA!), but I switched placement FROM the top of the scope to offset on the left side so I can see the bubble without breaking position. I also mount it as far forward as possible because at my age my eyes don't do the "up close" thing anymore. When almost ready to fire, one of my last prep steps is to check bubble with my non-shooting eye just in case I've inadvertently moved. If I was to set up a gun for a lefty, I would put the offset on the right side of the scope instead. Here is the view with the left eye.

 

[Deleted member 46119]

And another thing. Wouldn't the bubble be more accurate mounted on top of the scope. The farther away from the bore the more sensitive to can't. How much difference would it be mounting the bubble on top of the scope or the rail?

Yes farther away makes it more sensitive.

My bench rest rifles have the flip up type. Can't remember the name. Gets the level 2" or more above scope centerline.

Most of my hunting, tactical and practice rifles have a Vortex mounted so I can see it in my weak eye. The Remingtons also have an xTreme Acculevel rail.

 

[Greyfox]

For hunting I believe the difference in location on the rifle is not material. I think that fast and easy viewing while in your shooting position is far more important.

 

[Deleted member 46119]

For hunting I believe the difference in location on the rifle is not material. I think that fast and easy viewing while in your shooting position is far more important.

That's why I like the Vortex. Easy to see. Rock solid mounting.

Here is the flip up for target use Amazon.com : Scope Level 30mm Black : Gunsmithing Tools And Accessories : Sports & Outdoors

 

[Scot E]

I have the scoplevel flip up style on my precision airguns and rimfire guns and have never had an issue. They work great!

Scot E.

 

[jmitchell135]

So what happened with the guys that didn't think a level was necessary but bought one to try? Did it make your groups more consistent or no change?