Hold over and Under explained

[zini 1,939]

Hi all,

 

I received a PM from a friend that i want to keep anonymous asking me a question about hold over and under.

 

I didn’t have the text book answer myself only what I’ve always known after being taught in the military.

 

I got interested myself so i went looking for the answer on the net.

 

Here is what i have managed to find on the net put into a word document to explain hold over and under for everyone to read.

 

It explains which is which quite well.

 

Zini

Hold over and under explained.doc

[ghillies 209]

heres a chart with a tragectry on,(the arc shape line).

along the bottom is the distance,

the red lines is a laser,

the purle one is the cross hair.(at zero inch drop)

down the left hand side is the inch drop or rise above or below the cross hair line.

the black lines fanning out are the mil dots, or whare the mildots would be at diferent distances, because the further away you aim the bigger the actual distance between the dots.

 

basicaly holding over you put the cross hair above the target.

hold under you put the cross hair below

the point being to make the the pellet land on target by correcting the climb above or drop below (depending on the distance).

 

the scope actualy points down at an angle so that when the pellet comes out the barrel (and starts to drop because of gravity)it hits where the cross hair is at a set distance(your zero). thres actualy two points at two distances that will hit the cross hair dead on, the pellets path is actualy upwarsd untill it levals out at the high point on the chart then drops again beyond the second zero.(hense the 'arc').

 

at 25 yards you'd aim the cross hair lower than usual so the pellet hits,(hold under).

befor and after the two zero's you'd aim higher to hit by what ever to hit at whichever distance(hold over)

Edited January 5, 2010 by ghillies

[stealthy1 3,964]

That seems to cover it Zini, should help quite a few folk out

[sibaldib 6]

Nice one Si. I think the most important part of the document is the following sentence:

 

"...... you will have to be very familiar with the ballistics of your particular weapon and ammunition at all distances."

 

This is vital as you can sit and look at a programme like Chairgun Pro for hours and in theory it should be accurate, but for some reason and in particular at longer ranges it does not equate to the scope on my particular rifle. Also worth bearing in mind that not all scopes are true mil-dot scopes. This is why you need to use a trajectory chart that you fill in yourself and then memorise or write down the most used distances.

 

Cheers

 

Sib

[zini 1,939]

That’s exactly true Sib, I agree with you 100% mate

 

That’s why I designed my own trajectory chart which I think you have now and people can now download on here from the help section .

 

The computer software is great and I won’t knock it but to be 100% correct to your own combos best to do your own testing at different ranges to ensure perfect pellet placements.

 

When killing vermin at 30 metres and beyond as in all shooting at all ranges its only fair that you kill the animal the cleanest way possible and that means as good a POI as possible .

 

I think a simple way to remember which is which is to think about the cross hair itself.

 

If the cross hair is above the POI then its hold over

 

If the cross hair is below the POI then its hold under

 

I will do a camera thread with my scope cam on it later in the next few days hopefully .

 

It’s pretty easy to see with a .22 calibre pellet as the trajectory is so curved especially over 30 metres when the pellet drops off needing large amounts of hold over.

 

Si

[wuzzy 0]

sorry to but in "sib" ! but no commercial scope is "true mildot"as the scope manufacturer would have to pay royalties to the military you just need a scope thats pretty damn close and know the weight of your pellet and your rifles muzzle veloc- with said pellet an chairgun does the rest

[nasher1 258]

I have the same scope as you have on the gun you attached the video cam to, I have it attached to a .22 s410 its zeroed at 30 meters which means at 20 meters its one line under and at 40 meters its one line hold over, I like the reticule on the scope and find it easyer than a mildot

[zini 1,939]

Hi Nasher,

 

That depends on what magnification you have your scope set on pal.

 

Hold over /under changes with magnification changes.

 

I use x 10 to shoot and hunt and 20 metres is 1 mil dot hold under for me.

 

40 metres is 2 mil dots hold over.

 

I should imagine that you are using a lower mag setting on your Tasco pal than me.

 

Zini

Edited January 5, 2010 by zini

[JackReid 35]

Zini do you zero at around 30 meters with your setup? Do you zero on magnification x10?

I am just interested as I have never really thought of using that sort of magnification.

I've always felt for me even long range at best all I would need is x8 maximum (I only use upto x6)

 

Also does a scope hold its zero if you zero'd it in at say x6 and start shooting the same target on x12 for instance?

Just interested, havent given it a whole hearted try but assumed accuracy would be partially or totally lost, even on a good scope. Whats your thoughts?

ATB

Jack

Edited January 5, 2010 by JackReid

[mike white 1]

Hi zini is that correct mate i was led to believe that the milldot spacing was 3.6" at x10 zerod at 100 yards not x14 ?

[zini 1,939]

Hi JackReid,

 

Yes i always zero at 30 metres at x12 mag on both my rifles.

 

I then shoot at x 10 mag.

 

I use a bigger mag as sometimes i shoot at 45 to 50 metres so need my mil dots.

 

If i change the mag for normal shot 15 to 35 metres to say x6 and get to know their hold over when i have to bump up the mag to x 10 for the longer shots i would get confused and probably miss.

 

Changing the mag on a scope does not effect its zero mate that’s what they are designed to do so feel free to experiment pal

 

What does change unless you have the scope with the mil dots engraved onto the glass is the hold over points between different mags.

 

Hi Mike,

 

I couldn’t tell you pal as i found that on the internet.

 

I have read other articles which stated x 10 pal so it’s either wrong or a scope designed for x14. Who knows?

 

I always calibrate my own mil dots at x 10 mag so never really worry about any other mag mate, and i dont use the mil dots for range finding as i have a laser range finder on my rifle and a hand held one.

 

Zini

[mike white 1]

Hi JackReid,

 

Yes i always zero at 30 metres at x12 mag on both my rifles.

 

I then shoot at x 10 mag.

 

I use a bigger mag as sometimes i shoot at 45 to 50 metres so need my mil dots.

 

If i change the mag for normal shot 15 to 35 metres to say x6 and get to know their hold over when i have to bump up the mag to x 10 for the longer shots i would get confused and probably miss.

 

Changing the mag on a scope does not effect its zero mate that’s what they are designed to do so feel free to experiment pal

 

What does change unless you have the scope with the mil dots engraved onto the glass is the hold over points between different mags.

 

Hi Mike,

 

I couldn’t tell you pal as i found that on the internet.

 

I have read other articles which stated x 10 pal so it’s either wrong or a scope designed for x14. Who knows?

 

I always calibrate my own mil dots at x 10 mag so never really worry about any other mag mate, and i dont use the mil dots for range finding as i have a laser range finder on my rifle and a hand held one.

 

Zini

 

 

Yeh like you say you find what mag works best for you anway and work out your milldots , to be honest i think yeh the ballistic calculators help a tad but to be honest its trial and error anyway isnt it , i also use a laser rangfinder for range estimating so have never tried with milldots myself.

 

Atb mike.