How important is perfect level your scope to your gun?

[nervoustrig]

The top turret is the index point and even if the reticle is off, the gun will fire true if a level is placed in relation with the receiver's horizontal plane.

Okay I think I see what you are referring to. Yes, if the intention is to dial the elevation turret when shooting at varying ranges, it is preferable to index off of the turret cap (or some other external feature of the scope). In so doing, one can be reasonably assured the reticle will travel perfectly up and down.

Whereas when using the reticle for aiming (i.e. using mildots), it is better to index the reticle to the bore.

 

[Firewalker]

...It's that plane on the scope. That's indexed. It's the one you need a special jig to line up. The kind that all the gunsmiths use nowadays...

I read his instructions a half dozen times and asked for clarification. It's as clear as mud to me now. It must be the way to do it though. He giggled at me. He suggested my methods were outdated. He must know something I don't.

I went into my cave and did it with flint tools and a forked stick. Well see how far off it is shooting off the bottom dot. That's where the mammoth meets the tar pit anyway.

Yupper, it happens when I'm trying to do four things at once and my thoughts wander...

Lets try this again:
Scopes are made in a jig. The first hole is the top turret hole. The plane that is used to index on the scope for all other functions is that hole. If the center of that hole is lined up vertically with the bore, it's "true".

Along the way they reticle ring is installed and it's aligned to the crosshairs to the scope indexing plane so that horizontally and vertically, the top turret is perfectly aligned to the reticle center.

Mirror, plumb bob, wall target, jig or level, all methods seek to align the reticle crosshair with the bore for perfect alignment.

String has a large resolution, so do wall targets and even the mirror alignment has a lower resolution than a proper alignment jig.

A true level has about the same resolution as the mirror alignment and can be done in a mechanical rest without movement and its very quick to do.

Do as you wish, I still do a bunch of them every month and the box test shows alignment when tested.

 

[WobblyHand]

Interesting discussion on this. My take on levels comes from a machining perspective.

A carpenter's level has a sensitivity of 0.250"/foot. I'd bet the vials used on gun levels are at this point, maybe. Torpedo levels have the same vials.
A Starrett 98 series level sensitivity of 0.005"/foot - or 50X better
A Starrett 199. sensitivity of 0.0005"/foot - 500X better than a carpenter's level

I bought a cheap eBay level that is rated as 0.0002"/10". It's ridiculously sensitive. To use it I needed to calibrate it. I used a small surface plate and crudely leveled it using three adjustable legs. (Carpenter's level) It was difficult to find a level line since the bubble would peg on the side. Eventually after some refinements I got it "not pegging". A few more refinements and I got it to the point that I could flip the level 180 degrees and both sides weren't pegging. Finally got to the point where I could calibrate the level. Yeah, it was a pain in the neck.

One thing that I learned was a carpenter's level is not very good. The bubble just sat there, not moving, when a better level was off the end. If you use a real level you can detect if you get too close to it. This level was set up in my kitchen. When I was six feet or more away it read level. When I got within two feet, the bubble deflected. Why? Because the floor joist was ever so slightly sagging due to my nearby weight. Step back again, and it was level. Were my counter tops really level? Heck no, but the carpenter's level thought so.

Of course, using a level like this makes no sense for an airgun. But neither does a carpenter's level, because it is crude. Might give the shooter a clue if way off, but I'd bet using the horizon (if flat) is a better reference.

 

[Jaxjax]

I used to optically line up cross hairs after level scope base bottoms, but now I just use my phone with a level app. I just level & not using a bubble but .0 for XY with phone on my scope ring bottoms already attached in position & torqued. After that I lay scope in position & level off the top turret to .0 XY. Then carefully put the scope ring top caps on & torque em. Done... & seems to work fine for me. My shooting is 40 to 100 yards on home range. I have checked this routine out against a plumb line once & couldn't see a discrepancy. I am sure this isn't ideal to some, but I don't really even use my scope level when shooting, I just visualize it as I just can't be worried to watch that da.. thing while concentration on the shot.

 

[JimD]

It seems to me that all the methods that have been mentioned have not insignificant potential sources of error. For instance, I get how you can align the reticle with a plumb bob but how does that ensure the bore is directly in line with the plumb bob? In general, how do you level a gun? I don't think there is a way other than assuming something like a top or bottom picatinny is flat relative to a vertical line through the bore. Then you can level that surface. But the level is not perfect either as has been pointed out.

But I pretty much ignore all this and just make sure the flat bottom of the scope in the area of the adjustment knobs is parallel to the top picatinny rail. I use metal spacer blocks to take up most of the space and then a feller gauge to make sure the gap is the same on both sides. As long as the picatinny is flat and the scope is parallel with it I think it is mounted correctly. If the picatinny is not flat relative to a vertical line through the bore then the scope is not going to be in line with the bore but I also suggest the picatinny would also cause a problem with other mounting methods. I am trusting the machining of the gun.

I like the mirror idea but how does one determine the exact center of the objective bell of the scope? I see how you can get fairly close but I respectfully suggest at least my eyeball is not likely as precise an instrument as the machining equipment that built the gun.

 

[WoodWelder]

 

[Bedrock Bob]

After we all get done doing it our own way and finally stop screwing with scope alignment process hopefully we shoot the gun.

If cant and scope alignment is even a minor concern a guy needs to shoot comparative groups at a target at range to see if there is windage creep . Or maybe do the tall target test at 25. Why spend time trying to plumb the crosshairs perfectly if you don't test it to see if it worked?

With any method mentioned there may be some windage creep at range. At that point we decide if we are going to fiddle with trying to rotate the scope half a degree or just live with it. Most guys won't bother as long as the error isn't too extreme. Still it would be nice to know if your gun shot a little right (or left) at range.

If you dont shoot test targets you will never know if the plumb bob is off in your scope indexing plane or the resolution of your bubbles are adequate to plumb your complexly etched reticle to your highly polished and exquisitely crowned bore. Your pellets will all fly into the corn south of where you aimed and your blood pressure may spike as a result.

 

[orangeokie]

I see people attaching bubble levels and whatnot on there guns and scopes trying to get perfect level. How would you know your gun is even level? Since most guns aren't flat on top how would attaching a level on the barrel you know its even level. So when I install my scope. I hold the gun to where it looks straight and level for my eye. Then I loosen the scope rings and rotate the scope till the cross hair is level. I double check that gun is still level and cross hair is also level using only my eyes. No bubble level or any attachment. Am I doing it right or am I doing it the wrong way. When I go to my crosshair is level, that's all that matter or is there more to it than just having crosshair level during shooting.

I first level my tripod with its built in centering bubble level then clamp down the rifle just enough to hold it. I then level the rifle by placing a level across a square surface on the receiver and clamp it down tight. Finally, I level the scope either with a level set on top the turret cap or with a level screwed into my scope ring (ie. BLK) by rotating the scope in the rings, then tighten. I then look through the scope to see if the vertical crosshair is parallel to a hanging straight edge. If the rifle is level when you level your scope you are going to get more consistent accuracy IMO. This works for me with both PCPs and PBs.

 

[Bedrock Bob]

The turret leveling idea certainly does not work on the Sightron S1. After leveling the rifle and plumbing the crosshairs I tried it. Both with and without the cap. The upper surface on either is not something that is a reliable measuring plane.

I have a banana box full of old scopes from decades of shooting. Very few have flat surfaces up there. Very few have a surface that does not move a tiny bit.

I see where a tool that screwed on the threads might provide a stable point of reference on some of them. Others simply don't have enough threads to line a tool up. They are many different sizes and thread pitches.

A tool that centered the turret and leveled the scope would need to clamp the tube and index from the center of the turret. I can visualize how to make a tool like that but have never seen one. I'm not sure it would be much better than simply lining up on a plumb construction line. I understand the theory that this is the plane the scope is built from. I just can't figure out a good way to make use of that knowledge without a special tool to make it happen.

I still think the plumb line that pivots in the bore is the easiest way to line things up. It seems the shortest route to alignment and the least expensive way. You could bend a coat hanger in 60 seconds and spend zilch to line it up. No level needed. But that is just my personal opinion. It all gets you very close to where you need to be and any method will suffice as long as you do it carefully.

 

[Firewalker]

The turret leveling idea certainly does not work on the Sightron S1. After leveling the rifle and plumbing the crosshairs I tried it. Both with and without the cap. The upper surface on either is not something that is a reliable measuring plane.

I have a banana box full of old scopes from decades of shooting. Very few have flat surfaces up there. Very few have a surface that does not move a tiny bit.

I see where a tool that screwed on the threads might provide a stable point of reference on some of them. Others simply don't have enough threads to line a tool up. They are many different sizes and thread pitches.

A tool that centered the turret and leveled the scope would need to clamp the tube and index from the center of the turret. I can visualize how to make a tool like that but have never seen one. I'm not sure it would be much better than simply lining up on a plumb construction line. I understand the theory that this is the plane the scope is built from. I just can't figure out a good way to make use of that knowledge without a special tool to make it happen.

I still think the plumb line that pivots in the bore is the easiest way to line things up. It seems the shortest route to alignment and the least expensive way. You could bend a coat hanger in 60 seconds and spend zilch to line it up. No level needed. But that is just my personal opinion. It all gets you very close to where you need to be and any method will suffice as long as you do it carefully.

Go for it!

 

[Ta-Ta Toothie]

Whatever you do, don't waste your time with the Starrett Pocket Level 135A. I had 3 of them and everyone was off. Not Starretts best work. Darn shame cause it's the perfect size.

 

[Bedrock Bob]

A couple v blocks at right angles would sit on the tube and center the turret. An accurate level on top would position the scope perfectly. A tall sighting plane above the blocks would offer some bore centering capability. A jig like that wouldn't be too hard to make if you had the tools to do it accurately.

Lots of mounts sit a little sidesaddle on the dovetail. Especially on air rifles. Dovetails are not uniform in width and most mounts only reference one side of the dovetail. A perfectly level scope on a perfectly level rifle would often be perfectly misaligned.

However it's done it needs to be in reference to the bore. A level rifle and plumb crosshair should get you mighty close in most cases. But the critical error is bore alignment. The scope is effectively canted if the scope is not plumb with the bore. Unless you have some method for aligning the crosshair (or turrets) with the bore it's going to be a guessing game.

The mirror method is a lot more accurate if you hang a plumb bob from the bore. It gives a longer sighting plane and errors become much more evident. A plumb line above the bore is the most direct way of doing it that I can visualize. It offers a plumb reference point above the bore to line up the crosshairs (or turret). The other methods described don't seem to take the bore into account at all and seem (to me) to have a much greater potential for error.

 

[Smitty911]

View attachment 508135

I can see his left eye has a problem by the way his right eye keeps looking at it.

Smitty

 

[Jaxjax]

Lots of mounts sit a little sidesaddle on the dovetail. Especially on air rifles. Dovetails are not uniform in width and most mounts only reference one side of the dovetail. A perfectly level scope on a perfectly level rifle would often be perfectly misaligned.

This is true & drives me crazy..My BM500x is 1/2 x 60 which is basically Davidson dovetail. I run Harrells & D3 for proper fit. The universal sh,. is just that. There is no standard for dovetail.
I don't feel any of my SIII flat scope turrets rocking around, but I get what your saying. Since I punch 5 shot groups pretty much 85% of shooting at 3- distances I suspect I am wayyy more of a problem them my scope set up. My trigger work alone is good for .3 +improvement easy. Winter is coming so maybe I'll revisit all my scope mount setups to see how close or far off I really am just for kicks..

 

[Bedrock Bob]

Thermal variances cause me problems. Light changing in the evening. Scopes mysteriously moving 6 clicks every 50 shots. Wind and range estimation...

Scope misalignment has never been an issue for me using my crude Neanderthal methods. Scopes slip and twist on springers and you have to correct it often. A guy gets good at it with practice. But that dosent mean it's good enough for everyone.

My buddy got a .416 Barett a couple years back. He learned all sorts of tricks to shoot 2 miles out. Scope alignment is a big deal and he spends an entire day getting it right. He bore sights the rifle on a distant light on the horizon and tracks the scope to the limits to get it right before he shoots it.

The rounds are a smooth $10 each. He'll shoot up a $500 bill sighting it in and testing the scope drift on a tall target. Then another $500 developing a drop chart.

That's the only time I had ever seen someone use a tall target to check their scope alignment with the bore. But it makes sense for shooting distances like that. It's an easy test and it gives the shooter some really good feedback even at "reasonable" ranges.

It's a cool experiment if it only cost .02 a shot. I'm anxious to try it with a pellet gun after this discussion.

 

[Bedrock Bob]

The weather is bad so I made a little bore alignment jig today. I was taught this trick by my dad years ago. It's a quick and dirty answer to scope alignment with the bore. You can buy fancy jigs that work just like it but you can make one pretty quickly.

My father used a brass welding rod. I didn't have one handy. So I spun a copper wire in a drill to work harden it and get it straight. After I bent it I got everything on plane with a piece of glass.

You can see it great through the scope. It's a little wide but it works. I leveled and squared the scope with a plumb line and then checked it against the plumb bob. Everything lines up well.

You can get good reference with the reticle looking both ways (looking from the breech or muzzle). And it gives you a longer sighting plane if you are using a mirror.

It works. If you are careful I think you can get pretty good crosshair adjustment with it. And it could be made better with just a little tweaking. A gun with a muzzle break would need a bit longer rod. You could improve resolution by spraying half of it black. But it will get things mighty close to perfect just like it is.

 

[coastal drifter]

The weather is bad so I made a little bore alignment jig today. I was taught this trick by my dad years ago. It's a quick and dirty answer to scope alignment with the bore. You can buy fancy jigs that work just like it but you can make one pretty quickly.

My father used a brass welding rod. I didn't have one handy. So I spun a copper wire in a drill to work harden it and get it straight. After I bent it I got everything on plane with a piece of glass.

View attachment 508912

View attachment 508911

You can see it great through the scope. It's a little wide but it works. I leveled and squared the scope with a plumb line and then checked it against the plumb bob. Everything lines up well.

You can get good reference with the reticle looking both ways (looking from the breech or muzzle). And it gives you a longer sighting plane if you are using a mirror.

It works. If you are careful I think you can get pretty good crosshair adjustment with it. And it could be made better with just a little tweaking. A gun with a muzzle break would need a bit longer rod. You could improve resolution by spraying half of it black. But it will get things mighty close to perfect just like it is.

Did you use your flint tools to make that

 

[Bedrock Bob]

Did you use your flint tools to make that

Indeed. And the foreleg bone of an antelope.

 

[Motorhead]

The weather is bad so I made a little bore alignment jig today. I was taught this trick by my dad years ago. It's a quick and dirty answer to scope alignment with the bore. You can buy fancy jigs that work just like it but you can make one pretty quickly.

My father used a brass welding rod. I didn't have one handy. So I spun a copper wire in a drill to work harden it and get it straight. After I bent it I got everything on plane with a piece of glass.

View attachment 508912

View attachment 508911

You can see it great through the scope. It's a little wide but it works. I leveled and squared the scope with a plumb line and then checked it against the plumb bob. Everything lines up well.

You can get good reference with the reticle looking both ways (looking from the breech or muzzle). And it gives you a longer sighting plane if you are using a mirror.

It works. If you are careful I think you can get pretty good crosshair adjustment with it. And it could be made better with just a little tweaking. A gun with a muzzle break would need a bit longer rod. You could improve resolution by spraying half of it black. But it will get things mighty close to perfect just like it is.

Elegantly simple

 

[Jaxjax]

I just leaned some sh.. Bob , good stuff !!!! Ill be using that one if ya don't mind