Scope Levels- Why?

[basinman]

I put a level on my first long range rifle because after doing the research, I agreed it was necessary for long range accuracy. And since I verified that it does make a difference, I have put them on most of my centerfire rifles. But as some have mentioned earlier, the scope must be set up correctly when installed on the rifle.

 

[gusd]

Does this make sense?

 

[J E Custom]

Your barrel has no clue or preference at what angle it is shot at. Reticle is the only thing that needs to be level. You can shoot your stock at a 45 degree angle if the reticle is level. Just think about it for a second.

If you look at it this way, the barrel is never Level while shooting, it will always point up, unless you are shooting downhill. the bore has to be clocked level before you can level the horizontal recital level. the bore and the scope centerline should be one above the other and converge at one point/distance depending on the zero distance. In theory, if they don't converge to the same exact point, the rifle or the scope is not level and the farther you shoot, the bigger the error.

If everything is truly level, spin drift will be easy and precise to calculate.

The whole purpose of leveling everything is to do away with built in error and rely on shooter skills for those things that need to be compensated for.

J E CUSTOM

 

[LRNut]

But if you think about it for two or three seconds you understand the flaw in that reasoning. See above post

Not sure you are agreeing me or saying my reasoning is flawed...

 

[tnek13]

All of my scoped rifles, including 22LR, have levels and are in line with the bore and plumb bob to the best of my ability and the numerous gadgets that I have picked up over the years for that purpose. Then I shot each one to ensure alignment and consistency. LE Custom has explained why.

 

[Rich Coyle]

I have levels on all my rifles. The scopes are mounted to the axis of the action using a plumbob and the level aligned with the scope. Consistency, a quality I am always chasing. At my age my old eyes need the extra assistance. Note, a friend bought a computer printed plastic scope level which pulled apart after two shots. Buy a decent quality level.

I bought three. None were any good. I hope he has solved his problems.

 

[Mram10us]

I bought three. None were any good. I hope he has solved his problems.

How were they not any good? I've bought some amazon $5 specials and they worked

 

[Philward]

I am a bit nerdish and believe that any job deserves being done properly. My opinion and I'll stand by it.

I placed my rifle strapped down on a sled that was strapped down a on a weighted table that was tied to the ground. Line bore picture through barrel to target, set on level plain, and scope similar just for a reference starting point.
I used my machinist level, dev lines = 0.0001 of inch, to level the rifle. I used the same level on the scope.
Then I zeroed at 100 yards, stepped it out to 400 yards and set my bottom vertical CRS at 400 yards.

I do not use a level on my scope. I line on target, and when my vertical reticle is drifting centered up and down on POA I will slow and stop my breathing before squeeze. The rifle/scope is level with earth.
At short distance the lack of level is negligible as a miss by an inch is still deadly, but why take a chance? A quick death prevents pain on the animal's part and tracking, guilt on my part.

If you notice that the POI is drifting farther and farther to one side which becomes more severe as the distance becomes greater and greater, it might be a good time to head out and re-level your rifle/scope.

edit; I forgot one thing, sorry. I will hang a plumb bob at distance on a wind free day. I will set my rifle so the vertical retical is lined properly with the yellow string on plumb bob. I will then look thru barrel and ensure the yellow cord is through vertical centreline of barrel, best as my eye can tell. Yes, I overdo things, but I have fun doing it.

This is the first post I've read where anyone said anything about aligning to the bore of rifle. It's the starting point I would think, and everything should be based off that. JE Custom may have mentioned it.

Can spin drift be adjusted out with a windage adjustable base, or is it an exponential change the further you go out?

 

[LRNut]

Your barrel has no clue or preference at what angle it is shot at. Reticle is the only thing that needs to be level. You can shoot your stock at a 45 degree angle if the reticle is level. Just think about it for a second.

Ok, I just did the math using trig and similar triangles...a 45 degree cant on the rifle, assuming a scope height of 1.75" and a 200 yard zero would result in horizontal error of 3.7" at 800 yards - no thanks. A 10 degree rifle cant (with the scope reticle leveled) would result in a one inch error at 800 and a 1.5" error at 1200. Not huge, but if you are trying to hit a ten inch plate at 800 and only shoot 4 inch groups, you are giving up 1/3 of your allowable wind call error 50% of the time (the other 50% you increased it by 1/3). And in real life, after practicing, you might think you are seeing spin drift and learn to compensate.

So I will concede not as dramatic as I thought.

Again, this is for the reticle level but the rifle canted.

 

[LRNut]

Can spin drift be adjusted out with a windage adjustable base, or is it an exponential change the further you go out?

Not sure what you mean with a windage adjustable base, but if you are using the model with the screws, get rid of it and use a rail. You can minimize spin drift by zeroing at longer ranges.

Here is what I do: I zero at 500 yards on a calm day (mornings). I then adjust by SIG Kilo 2400 ABS 200 yard zero with a horizontal offset so that when I range the 500 yard target with a no wind condition, the required wind hold is zero - you have to play around with the required offset until you get a zero wind hold (which because the wind is zero, the wind is the calculated spin drift). My offset at 200 is normally like .2 or .3 MOA; I will take that any day.

 

[Rich Coyle]

To each to their own, but in this case it seems to be ignorant to not use a bubble level when shooting at long range!?!?

Ignorant is uninformed. Stupid is inability to learn.

 

[milo-2]

Ok, I just did the math using trig and similar triangles...a 45 degree cant on the rifle, assuming a scope height of 1.75" and a 200 yard zero would result in horizontal error of 3.7" at 800 yards - no thanks. A 10 degree rifle cant (with the scope reticle leveled) would result in a one inch error at 800 and a 1.5" error at 1200. Not huge, but if you are trying to hit a ten inch plate at 800 and only shoot 4 inch groups, you are giving up 1/3 of your allowable wind call error 50% of the time (the other 50% you increased it by 1/3). And in real life, after practicing, you might think you are seeing spin drift and learn to compensate.

So I will concede not as dramatic as I thought.

Again, this is for the reticle level but the rifle canted.

Thanks for the math! Is there any error straight up-straight using your calcs?
The 45 degree was a stupid statement-comparison, but I feel if someone wants to cant their stock 2-3 degrees for comfort, level the scope to accommodate, no ill effects. Canting the scope 3 degrees a whole different issue.
I am not one to tell people they cannot shoot within an inch at 800, but an inch off at 800 still destroys a paint can or anything bigger for that matter.

 

[Mram10us]

Ok, I just did the math using trig and similar triangles...a 45 degree cant on the rifle, assuming a scope height of 1.75" and a 200 yard zero would result in horizontal error of 3.7" at 800 yards - no thanks. A 10 degree rifle cant (with the scope reticle leveled) would result in a one inch error at 800 and a 1.5" error at 1200. Not huge, but if you are trying to hit a ten inch plate at 800 and only shoot 4 inch groups, you are giving up 1/3 of your allowable wind call error 50% of the time (the other 50% you increased it by 1/3). And in real life, after practicing, you might think you are seeing spin drift and learn to compensate.

So I will concede not as dramatic as I thought.

Again, this is for the reticle level but the rifle canted.

That doesn't sound right to me, but I haven't done the math.

 

[LRNut]

Thanks for the math! Is there any error straight up-straight using your calcs?
The 45 degree was a stupid statement-comparison, but I feel if someone wants to cant their stock 2-3 degrees for comfort, level the scope to accommodate, no ill effects. Canting the scope 3 degrees a whole different issue.
I am not one to tell people they cannot shoot within an inch at 800, but an inch off at 800 still destroys a paint can or anything bigger for that matter.

There is always the possibility my math is wrong; be happy to send my Excel file if someone wants it.

Well, only if you shoot one hole groups at 800 - if your groups are the width of the paint can any error (cant, wind call, etc) creates the probability of a miss. Wait...is that spray paint or Sherwin-Williams?

But like I said, the difference in the rifle canted/scope leveled are not as large as I would have thought.

Any time I do math I always like to remember the old joke: What is the difference between an engineer and an accountant? Answer: the accountant knows he isn't an engineer. (Accountants think that is pretty funny since engineers think accounting is "just math.")