Scope leveling

[Tim L]

What level of accuracy is actually necessary, and how do we get it?

There are a few systems out there, but I am always left thinking there are a few assumptions made when performing the task.
Levelling blocks assume the reticle is set exactly perpendicular to the base of the turret block.
All of the systems assume that when the scope rail is horrizontal, its centre point sits exactly vertical to the centre of the bore.
I guess the question there is, does it matter?
I know that even with top quality rings, when the bottom half is fitted, if you move a bubble that's level on the rail, it is often not level across the top of the bottom rings.
So, if we just go for "close enough is good enough" for scope to barrel relationship, the bit that's actually important is that, when shooting, the vertical reticle line is as close as possible to being actually vertical.

If that's correct, wouldn't a plumb line 30m away be a more accurate method of alignment than a 1-inch bubble level? (Not forgetting that we then set and rely on a tiny bubble level in the end anyway.)

[Rich4]

Realistically the only relevant items to me are the scope level to actual reticle travel not the reticle itself which I always check regardless of manufacturer, ie tall target test, position then of the bore underneath is a consistent offset provided the gun is always leveled to the scope level, I only use scope mounted levels for this reason and if swapping around any tilt between rail and bore axis is irrelevant

[Tim L]

Realistically the only relevant items to me are the scope level to actual reticle travel not the reticle itself which I always check regardless of manufacturer, ie tall target test, position then of the bore underneath is a consistent offset provided the gun is always leveled to the scope level, I only use scope mounted levels for this reason and if swapping around any tilt between rail and bore axis is irrelevant

Yep, agreed. Tall target test is the best/only way to confirm vertical travel.
So what's your process to get the scope level prior to shooting? (Assuming you want a 1st time pass on the tall target.)

[Rich4]

Well actually even though I’ve cast a dispersions on brand name to reticle plumbness, pretty sure thats not a word?
Out of multiple NXS a golden eagle and 2 bushnell elites I haven’t actually found one where it hasn’t agreed with the turret housing base flat, I do use a machinists level on the mill bed to setup the tube level prior to mounting, all cheap Chinese levels from evilbay, but I’ll take it, I just can’t bring myself to trust without verify.

[Rich4]

Sorry I just realised I didn’t really answer the first question, I use the mill table with parallels and machinist level to set the tube level to the flat of the turret housing base, then install the scope on the rifle in question and adjust for eye relief, then from the buttplate I sight the reticle into the bore centre by eye as that’s close enough for me, I’ve won no major awards so take my advice for what you paid for it, but seems logical and has worked well for me.

[MarkS]

Level on top of action/scope rail.
Align reticle to a hung plumb line.
I used to always struggle to get reticle "level" until I went to the hung line method - easy and it works.

go to 3.15min
https://www.youtube.com/watch?v=fmER5w3WBPI

[majaci@bigpond.com]

To avoid dealing with hung line, for the bench purposes I simply use rail mounted bubble level against the scope mounted level. Quick easy and accurate.

[6.5x55ai]

Scope aligned scope centre thru bore centre using a alignment tool from Brownells. In conjunction with plumbob to align with vertical section of reticle.
Only use levels that attach to the scope. First level used for F Class was a US Optics one that attached to the rail and was miles out.
I lower the plumbob weight into a bucket of water to dampen any swing about of the line.
Sometimes I put a backing sheet behind the plumbob to give better visual definition.

Have Burris Black Diamond, Leupy 8.5 - 25, 24x higher grade of Bushnell, Nightforce NXS and some cheaper scopes. Of them all only the Nighforce turret is true to the horizontal reticle.

[MarkS]

To avoid dealing with hung line, for the bench purposes I simply use rail mounted bubble level against the scope mounted level. Quick easy and accurate.

So how do you know "scope mounted level" is aligned with the reticle?

[majaci@bigpond.com]

To avoid dealing with hung line, for the bench purposes I simply use rail mounted bubble level against the scope mounted level. Quick easy and accurate.

So how do you know "scope mounted level" is aligned with the reticle?

Vertical line test, done once for the lifetime of that scope with bubble fitted and never removed again