Scope and Rifle leveling - flashlight and gravity.

[Don.Chipmunk-slayer]

After talking about re-zeroing my scope, some suggested that my scope itself might not be level. @TimeRabbit mentioned the flashlight technique.

Oddly enough, I noticed a video about exactly that on YouTube a few days ago. Being the old, retired guy I am, I was up at 3am this morning and found the video.

After watching, I went out to the garage (where I used my new rifle rest for the first time) and after leveling the rifle, I checked the scope. Of course it was a fraction off (not too bad for an eyeballing job though).

So I pulled the tops of the scope rings - making sure several times the rifle stayed level - and adjusted the scope with the screws to the rings attached, but loose.

Once the crosshairs were true, I checked the rifle leveling several more times, and slowly tightened each screw (4) until everything was snug. When they were tight, I checked the level a final time, and called it good.

Now, I really do have to zero the rifle all over again.

 

[Struckat]

Good timing as I have a scope to level this morning. I normally use a combo of plumbob and mirror.

 

[Racer88]

Yep... I've done it. Works great. I did a write-up. Reading this will be a bit faster than watching a 13-minute video.

I set the rifle up on the bipod and a big rear bag. <--- if you don't have a rifle stand / rest.

Ah.. but, you can't get far enough back to focus the scope on the plumb line, eh? Unless you've got at least 10+ yards of space in your house. Most parallax have a minimum of 10 yards or more.

So, here's the trick. You turn the rifle around, with the BACK (ocular lens) facing the plumb line on the wall. Then you shine a flashlight through the scope's objective lens (backwards). This will project a sharp shadow of the reticle on the wall! COOL!

I put a bubble level on the rifle and leveled it. Then I locked the bipod down (Pod-Loc).

It helps to turn the ambient light off / down to better see the image on the wall. So, I turned off the hallway and bedroom light. Also... you may find that adjusting the scope's zoom ring (all the way to the highest power) will make the reticle image sharper / easier to see. You might also fiddle with the diopter focusing ring to get a sharp reticle shadow.

I shined the light through, thinking I did a great job previously leveling the scope with the bubble level on the turret method (and that turret MUST be level, right?).

WRONG!

I put the bubble level on the turret to confirm that it was level with the rifle. It was. But, the reticle was not aligned with the plumb line, eh?!? It was off a bit! So, as it turns out, my scope turret is NOT level with the reticle.

So, I loosened the scope ring screws and tweaked the scope until the reticle was dead on with the plumb line. I did it first with the reticle off to the side a bit (making it two parallel lines with an even gap all the way down).

Then I moved the rifle over to superimpose the reticle on the plumb line to confirm:

BOOYA!

I tightened the scope ring screws in a "criss-cross" pattern, maybe an eighth of a turn at a time, ensuring the gap was even on both sides and pausing to check the projected reticle image again and again. You will find that, sometimes, as you tighten the ring screws, it can turn the scope (unlevel). It can be frustrating until you get the hang of it.

After torquing the screws down to spec, I checked the projected reticle image again. Dead on.

Next, I loosened the screw on my scope bubble level and re-leveled it to coincide with the reticle. Re-tightened it, and now everything is balls-on level!

 

[BlackICE]

If your turrets are not aligned with the reticle you may have a problem if you make dial Corrections for windage or elevation. On quality Scopes I would insist that turrets are lined with the reticle otherwise it's a Manufacturing defect!

 

[Racer88]

If your turrets are not aligned with the reticle you may have a problem if you make dial Corrections for windage or elevation. On quality Scopes I would insist that turrets are lined with the reticle otherwise it's a Manufacturing defect!

How many people even know how to check it... or care to check it?

The reality is that for most shooters... it doesn't matter... and won't make a difference.

 

[Jfk742]

A deck of cards or feeler gauges between the bottom of the scope and the rail will help get the reticle and bore aligned when you mount the scope.


Love that flashlight trick, I’ll have to double check my setup with that.

 

[nervoustrig]

Please bear in mind that any scope mounting strategy which starts with a spirit level to level the gun is making a variety of assumptions about the perfectness of the gun, the scope, and the scope mounts.

Granted, the result will almost always be better than eyeballing it, but not as certain as aligning the reticle to the bore.

 

[manabeknives]

Look up the "Tall target test" for an additional test to check your scope's tracking once it is leveled

 

[Racer88]

Look up the "Tall target test" for an additional test to check your scope's tracking once it is leveled

Yep!

I later found out that the range I was using was not actually 100 yards. It was 96 yards (we measured it). So I had to recalculate based on that, and my click value was actually 0.244... not nearly as bad as 0.235.

Now... for a centerfire rifle firing at targets 300, 500, 600, 1000 yards away... this can make a difference. For air rifles at less than 100 yards? My guess is "not so much."

ETA: I forgot I made this video. My ballistic calculator app has a built-in feature to calculate turret click value.

 

[nervoustrig]

Relatively small cant angles can produce meaningful error at 100 yards due to the loopy trajectory of pellets.

For example, a gun zeroed for 30 yards shooting at 100 yards with a scope canted by 2 degrees will be off by about 0.6 inch.

By comparison, canting the gun by the same 2 degrees will be off by 1.0 inch.