Bubble level??

aroshtr said:
Elimination cant in the RIFLE isn't what is really important. Eliminating cant in the SCOPE is. One of these days I will film a demonstration showing this, as most people do not think it is possible to shoot at long range if the gun is not perfectly level. We do this all the time with archery equipment, and I have set up several rifles where the gun was not level (for shooter comfort), but the scope is, and they shoot true out to 1000 yards.

Joel
Click to expand...

Your curved bullet path (drop) (minus wind) due to gravity is defined in a plain that is aligned with the pull of gravity. If your windage reticle (sight plain) is not parallel and aligned with bullets plain of flight there will be a divergence. if your scope is properly plumbed in relation to gravity and your rifle is canted right and you have zeroed to 100 yds in that condition, your bullet will have started it's path to the left of the vertical sight plain, traveling to the right to converge with that plain, and continuing to diverge to the right, away form the vertical sight plain. The farther down range your POA is the farther right your POI will be. This is a physical and geometrical fact.
 
MontanaRifleman said:
Your curved bullet path (drop) (minus wind) due to gravity is defined in a plain that is aligned with the pull of gravity. If your windage reticle (sight plain) is not parallel and aligned with bullets plain of flight there will be a divergence. if your scope is properly plumbed in relation to gravity and your rifle is canted right and you have zeroed to 100 yds in that condition, your bullet will have started it's path to the left of the vertical sight plain, traveling to the right to converge with that plain, and continuing to diverge to the right, away form the vertical sight plain. The farther down range your POA is the farther right your POI will be. This is a physical and geometrical fact.
Click to expand...

So the rail mounted level, and the plum line trued reticle, will have you covered correct? I feel it does as I have not had an issue doing it this way.

Jeff
 
MontanaRifleman said:
As long as they both agree then both are aligned to the bullets plain of gravity.
Click to expand...

Yep, I just did one this afternoon. Checked the rail top with a small level as I mounted the level on the rail and they agreed. Then , watching the level, trued the reticle perfectly to the plumb line. Just like I always have done. After the barrel is broken in and load development, I will shoot the line as I posted earlier for the final check.

Thanks

Jeff
 
Broz said:
Yep, I just did one this afternoon. Checked the rail top with a small level as I mounted the level on the rail and they agreed. Then , watching the level, trued the reticle perfectly to the plumb line. Just like I always have done. After the barrel is broken in and load development, I will shoot the line as I posted earlier for the final check.

Thanks

Jeff
Click to expand...

Yeah, as long as the reticule is lined up with the center of the bore and plumbed up and the levels reflect that you should be good to go.
 
A hypothetical math example. Scope is plumbed and rifle is canted say about 10 degrees. Scope is mounted 2" above center line of chamber. At 10 degrees right cant let's say the center of chamber (and bullet) are 0.2" left of center of scope. Our zero is @ 100 yds. When fired, the bullet travels right in relation to the line (plain) of sight to converge on the zero point. At 200 yds, the bullet has now gone from 0.2" left of line of sight to 0.2" right of line of sight. At 300 yds the bullet is now 0.4" right of LOS. At 1000 yds, the bullet is 1.8" right of LOS. Not a huge deal.

If we move the zero out to 200 yds, the effect is smaller. At 1000 yds the bullet would be 0.8" right of LOS.
 
Mark, you are exactly right, and I am in no way trying to argue, or disagree with your and science.

I was a little slow at doing my math by hand and compass drawings to get some actual figures. So, I guess since I did the math I will put what I came up with.

1.75" Sight Height, I actually came up with about .3" from center-line at 10 degrees.

If you were 10 degrees off with the rifle (Which would be blatantly obvious)
100yrd Zero = 2.7" off center at 1000 yards
200yrd Zero = 1.2" off center at 1000 yards
300yrd Zero = .7" off Center at 1000 yards

Most of my rifles have a 200 or 300 yard zero for my drop data/site tape, but I usually sight in and set my elevation and windage turrets at 500 yards. This helsp make up for any slight errors in my data. So in theroy If I set my windage at 500 then I will only be off .3" at 1000 yards from my gun being at some ridiculous 10 degree angle. Now when I set my guns up for a comfortable feel, I would bet that I am well within 5 degrees of square, and all these numbers would be about 1/2 their values.

I guess the point I am trying to make is that too many guys try and make this complicated and worry that if it isn't perfect then they won't be able to shoot accurately at long range. When the truth is, if you eyeball the gun, or use some other half *** method to get you close, it really is no big deal. Especially if you zero at 200. It is even better if you set the windage and elevation at your expected mid range shot distance. In this case the margin of error is much smaller than any gun or human being is capable of shooting.

The take away..... If it makes a guy feel better to spend your time and money on fancy gadgets and levels to get the gun perfectly level to the scope, that's fine. But for me and lots of other guys, my time is better spent shooting and confirming my drop data.

Joel
 
Joel, We could have figured out the 10* cant bullet offset with a little trig but it's been a long time since trig class so so I just guessed it :)

I can't argue that the error isn't all that much, especially if you zero at longer ranges. In fact zeroing the windage reticle at 500 or 600 yds while zeroing the elevation at 200 or 300 would probably be a real good idea... glad I thought of it :D

But when it comes to LR, I figure every little bit helps. It doesn't take me long to set up a level so I figure I'll do it.
 
I should have asked my 12 year old, and he probably could have told me how to do the math.:D

I think it is just as important to zero the elevation at 500 just like the windage. Just use your chart and see what it calls for (6.75 moa in my case). Sight in, and when done, move the turret to 6.75 moa and lock it down. If I end up a click of at my actual zero, no big deal. It will end up being a click closer at 1000, than it would have been if I only shot the gun at 200. Thats where 1 click can actually make a difference.

It is a little short cut if your drop data is not exactly perfect. Do my last few posts make me sound lazy???:rolleyes:
 
After leveling a scope to a rifle, I set up a plumb line at 100 yds. or so and with the rifle clamped in my gun vise, I run the elevation turret up and down the plumb line to fine tune tracking before firing any rounds. Once satisfied that the scope is tracking plumb, I tighten down the bubble level. I like the Hollands level by the way, it is a nice piece of equipment and once you have it set up on a scope it makes remounting much quicker if you need to remove and reinstall the scope later on. From there I zero at 100 yds. and check tracking by dialing elevations and firing at even intervals throughout the turret adjustment range. This will save a bunch of ammo, I know the scope tracks properly before firing.

Mark
 
MontanaRifleman said:
Joel, We could have figured out the 10* cant bullet offset with a little trig but it's been a long time since trig class so so I just guessed it :)

I can't argue that the error isn't all that much, especially if you zero at longer ranges. In fact zeroing the windage reticle at 500 or 600 yds while zeroing the elevation at 200 or 300 would probably be a real good idea... glad I thought of it :D

But when it comes to LR, I figure every little bit helps. It doesn't take me long to set up a level so I figure I'll do it.
Click to expand...



How about 10* @ 600yds (I think it was 10*, it's been a while since I read the article)

Aim Cant Effect.jpg


t
 
MontanaRifleman said:
That's quite an offset, especially for only 600 yds. So I guess you aligned your elevation reticle with the black tape? What was your zero distance and how high is the scope mounted?
Click to expand...



Mark,

I did not conduct that test. It was a write up I read a while ago, I know it was 308 & I believe it was an AI but don't quote me on that. Yes, the reticle was aligned with the black bar as to repeat as best as possible. I don't recall the scope height so I can't really comment on that. When I read the article I thought this pic was a great example & saved it for discussions such as this one.


t
 
That is an interesting pic for sure but it seems mathematically impossible. If the zero were @ 100 yds the 600 yd offset should be about 1" if it were 10*. My curiosity is spiked so I'll have to give it a try myself :rolleyes::)

Sounds like a good experiment for a 6-284 with a nitrided barrel gun)
 
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