Scope Mount Spirit Levels

[Stuck]

I've seen a few people in competitions using spirit level bubbles attached to their scope mounts but for the life of me I can't work out why it matters if your rifle is level (I mean left to right obviously).

Could someone fill in the gap in my understanding please because I honestly don't understand why it matters... zzzzom


Thanks,

Mick.

[ovenpaa]

Anti Cant devices (levels) are used to keep the reticle level as external references such as butts sometimes slope to one side, if they are used as a reference this can lead to errors. A couple of degrees of cant can lead to errors of up to 24" at 1000 yards.

[TJC]

I don't think it is one of the more important issues for long range but to give you a feel a typical .308 round fired at c2700fps with 6 degrees of cant will put you about 5" off centre. 20 degrees puts you off by c15".

There was a great photo at the Snipershide Cup this where the only guy to clear the 1200-yard shoot is photographed taking a shot with his bubble level showing a ridiculous amount of cant. If you have all day to make a shot it is a factor, if you are in a timed comp there are other factors you will probably want to focus on first.

[Stuck]

Thanks for the replies chaps, but I still can't work out why it matters.

For example, the firing point that my bipod is sat upon may not be parallel to the target but surely the point of aim is the same even if my reticle isn't parralel with the centre line of the target?

I'm obviously missing something...

[TJC]

It is the relationship between point of aim and then point of impact. Cant in the first results in change in the latter.

Have a look at the .22 example target in the link below:

http://www.accurateshooter.com/optics/c ... of-impact/

[EagerNoSkill]

Brian LITZ book
Canting distorts the windage line
If you cant it distort the waterline introducing elevation
Thus a windage change also then has elevation changes added

ENS

[Maggot]

I use a scope mounted on as it can be calibrated to the scope which in turn is calibrated to the bore using the Wedge system made by the Shooting shed.

I dont like the rail monted ones as some of the cheaper ones dont align well, also, if you want cant, you can set it using the scope mounted bubble.

I was lead to believe that cant in itself was not an issue as long as you were consistent and zeroed for it (TR shots all used to can once...or was is small bore.... sign85 ).

However, given we shoot at a 5" V and a 10" bull at 1000 then I am afraid I disagree...cant is significant in some disciplines and to be avoided.

Actually, if you are near the line its a probem in any long range discipline and one constant you can fix quit easilly.

Cant is an odd thing, I find that I am convinced my cross hairs are vertical, but check the bubble or a decent datum and I am off...wonky....normal I guess

I recently heard one KIA at a local club holding court (you know the type...jacket like a cub scouts blanket, mostly from blue peter and frosties packets) and commenting on my Dolphin.

Quite offensive actually.

Now I was only there for a quick chrono session, and he did not clock I was wearing actives :roll:

"I dont know why people spend all this money on rifles like that, and those level things are a waste of time, etc etc, drone drone".

I rounded on him and politely pointed out the errors and what I was trying to achieve (and still am).

All BS, turned out he was a LR pistol shooter who really should have known better....

In itself a level wont win you a comp, but it may keep you the point or two it takes to win the comp .

[Maggot]

I've seen a few people in competitions using spirit level bubbles attached to their scope mounts but for the life of me I can't work out why it matters if your rifle is level (I mean left to right obviously).

Could someone fill in the gap in my understanding please because I honestly don't understand why it matters... zzzzom


Thanks,

Mick.

Think about it this way Mick.

Your scope center and bore could be up to 2" plus apart, seperated vertically by a mount etc.

Assuming no wind, alright, assuming a bloody vaccumm and the world actually stops turning (someone is bound to bang on about spin drift, witch craft etc etc)

As long as the two are aligned vertically, then gravity acts upon the bullet along the length of the bullets trajecory AND the line of sight (both being theoretically the same). POA and POI should be the same

If you cant, say a degree or two to the right, your point of aim and trajectory (well, angle of launch is more accurate)will be at an angle, so the bullet will not be fired with the barrel pointed up in the air in a perfectly vertical alignment, so there is now a sideways component and the bullet will travel to the right. Gravity will do it's thing, and as far as you were concerned your cross hairs were dead center...but the rifle is now no longer pointing dead center.

I guess in theory it should also impact slightly lower as well because you have also disturbed elevation a tad as the bipod does not rotate round the bore either and is even lower then the scope bore relationship.

The best way to look at it is to take a protractor and place it perpendicular to a flat surface.

Think of the curved section as a trajectory then tilt it.....there is now an angle between the protractor and the surface, so gravity will act along the curved surface (trajectory) and pull the bullet down off axis...I think wtfwtf

Hey, it worked with squaddies :lol: