Help me understand

Ty89m

Member
Joined
Jan 6, 2014
Messages
14
I've just built my first semi-precision rifle (18" AR-15) and purchased my first high end optic (Leupold Mark 6 3-18) and am having a difficult time understanding "parallel/level with bore"

I'm using a Bobro 34mm one piece mount. For my first attempt at aligning the reticle, I leveled the rifle by using a spirit level on the flat top of rcvr, and then used a plumb bob to align the reticle with the plumb line. Basically, wouldn't this be good enough? I'm about to order either a scope or rail mounted can't indicator, and figured I'd once again use the cant indicator to level rifle, and readjust scope so it's aligned with the vertical plumb line. I wanted to add, the base of my rcvr and base of one pc mount are not level with each other, does that really matter as long as the reticle is plumb? Why do I see mention of aligning reticle with the bore, for example, using the EXD tool? Am I overthinking this?

My thought is, buy the optic mounted anti can't indicator, level rifle, hang plum line, align vertical cross hair with line, the adjust can't indicator unil it shows level when reticle is level with plumb line. Is that good enough out to 600? I doubt the rcvr/barrel/mount is perfectly true, but that's not really something I can fix.

I basically just want to get this done right so I'm confident that any misses are my own fault and not from a misaligned reticle. Should I invest in something like the EXD tool? Or will my cant indicator plus plumb line get me darn close? Seems as long as the vertical cross hair tracks straight up when adjusting elevation, not much else should matter.

Sorry for the indirect question, but this reticle leveling thing is driving me nuts!

Thanks!

Ty
 

WildRose

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Joined
Feb 3, 2011
Messages
14,831
Location
N. Texas and S. Africa
I've just built my first semi-precision rifle (18" AR-15) and purchased my first high end optic (Leupold Mark 6 3-18) and am having a difficult time understanding "parallel/level with bore"

I'm using a Bobro 34mm one piece mount. For my first attempt at aligning the reticle, I leveled the rifle by using a spirit level on the flat top of rcvr, and then used a plumb bob to align the reticle with the plumb line. Basically, wouldn't this be good enough? I'm about to order either a scope or rail mounted can't indicator, and figured I'd once again use the cant indicator to level rifle, and readjust scope so it's aligned with the vertical plumb line. I wanted to add, the base of my rcvr and base of one pc mount are not level with each other, does that really matter as long as the reticle is plumb? Why do I see mention of aligning reticle with the bore, for example, using the EXD tool? Am I overthinking this?

My thought is, buy the optic mounted anti can't indicator, level rifle, hang plum line, align vertical cross hair with line, the adjust can't indicator unil it shows level when reticle is level with plumb line. Is that good enough out to 600? I doubt the rcvr/barrel/mount is perfectly true, but that's not really something I can fix.

I basically just want to get this done right so I'm confident that any misses are my own fault and not from a misaligned reticle. Should I invest in something like the EXD tool? Or will my cant indicator plus plumb line get me darn close? Seems as long as the vertical cross hair tracks straight up when adjusting elevation, not much else should matter.

Sorry for the indirect question, but this reticle leveling thing is driving me nuts!

Thanks!

Ty
The easiest way to get it right is to use one level on the flat top of the reciever and another on top of the scope body. Get both bubbles equally centered and you are good to go.

The next easiest is a boresighter with a columator. Far less likelihood of starting off with an error with those two methods than any other.

The plum line works great if you have absolutely zero wind and have the rifle locked down in a vise otherwise though it is pretty easy to build in an error right there.
 

westcliffe01

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Joined
Jul 6, 2011
Messages
1,270
Location
Near Napoleon,MI
The ultimate test is to shoot at a tall target which has a truly perpendicular line on it (potentially drawn on the paper in the field and verified with an accurate level) then set up the rifle with the receiver level, fire a shot, crank it up 5 MOA, shoot another, and keep going until you run out of travel or target.

If your POI on the target follows the vertical line, you are all set. If it does not, you probably have an indication which way it is off. A canted scope will cause you significant issues at long range where the bullet will be displaced laterally as well as in elevation whenever you dial up some elevation on the scope.

When doing the test above, you need to minimize wind impact, so keep the range modest (100yds) and try to pick a calm day. And make sure the rifle stays level when shooting...
 

Ty89m

Member
Joined
Jan 6, 2014
Messages
14
Thanks guys, I've been doing the plumb bob in my house at the other end of the long hall, so no real issue with wind.

Ordering up an anti-cant indicator tonight. I initially tried with the Wheeler Prof. reticle leveling kit, and found that when leveling the rcvr with the top turret, that when I then looked at my plumb line with a level rcvr, that it was pretty far off. After adjusting it to be level with the plumb line (with the rcvr still level) and setting a level on top of the elev. turret, it now shows it being out of level.. I'm assuming this would mean the turret is not totally level/flat.

Thought about trying my feeler gauges, but the base of my one piece Borbro mount isn't level when compared to the flat top of the rcvr. Still considering ordered the EXD alignment tool, as I'm running out of options. I will certainly run a vertical tracking test when I feel confident I've got a good starting point though. Thanks again!
 

MontanaRifleman

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Joined
May 21, 2008
Messages
6,186
Location
South of Canada and North of Wyoming
I do the plumb bob method and align the reticle to the center of the bore (bolt removed). There's a lot of ways to skin the cat, but IMHO, the plumb bob is the best. If outside, the wind can mess things up, but on a calm day or mild breeze, it's fairly easy. Once the reticle is aligned with the bore, then tighten down the ring screws and set the level. Need to recheck everything as you tighten down ring screws and level screws.
 
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