Need help to settle and arguement

So I need help.

To cut a long story short I'm currently having an argument with my hunting buddy about how far out our rifles are. Mine's out, I took i big knock and needs sighting in I know that.

Not sure if he's having sympathy pains but says at 100m he's 6 inches high. That's fine we both agree. However where the argument starts is if he's 6 inches high at 100m, how high is he at 200m? We both normally sight in spot on at 200m and for arguments sake are 2 inches high at 100m. Then the shit hit the fan and all sort of threats have been made.

I'll admit I don't know enough about ballisitics and physics to work equations out, i buy factory ammo and use the info on the back of the box for bullet drop etc. By my reckoning if he's 6 inches high at 100m, and normal bullet drop of 2 inches over 200m, he should be 4 inches high at 200m. I'm hoping that I'm not a complete moron here but he reckons that at 2 inches high at 100m, he's 8 inches or more high at 200m. I'm struggling to see how, but like i said don't know loads about this, if someone could explain in simple terms who's right I'd really appreciate it. I'm hoping i'm on the winning side and save myself a box of beer.

If it helps, he fires a 6.5X55, hand loads but I don't know bullet weight/grain weight.

Cheers

You are right.

OK so I ran some numbers for a 140gr SP at 2700fps. If its 6" high at 100m then at 200m its a bit over 7" high before dropping to be zeroed at 300m.

Reason being is the bullet (in this example) reaches the top of its trajectory curve around 175m before starting to drop.

Same bullet and velocity shooting 2" high at 100m should be zeroed at 200m. Top of trajectory in this case is at around 100m.

Assuming a scope height of 1.6" above the rife bore.

Lets just say his hand load is a 140 gr sst
and
lets just say he's just over 2700fps
If this is the case or close and he's 6 inches high at 100yrds he'll have roughly a 350yrd zero which will put him just over 8" high at 200 yrds.

Even if he's using a standard interlock type 100fps slower he's still zeroing about 320 yrds and at 6" high at 100 puts him over 7" high at 200

You are right but by my reckoning 6" high at 100 aint good for f all

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Originally Posted by Gibo

You are right but by my reckoning 6" high at 100 aint good for f all

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Um....ah ......... its all good if you want to miss that 100m headshot

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Originally Posted by NZShoota

OK so I ran some numbers for a 140gr SP at 2700fps. If its 6" high at 100m then at 200m its a bit over 7" high before dropping to be zeroed at 300m.

Reason being is the bullet (in this example) reaches the top of its trajectory curve around 175m before starting to drop.

Same bullet and velocity shooting 2" high at 100m should be zeroed at 200m. Top of trajectory in this case is at around 100m.

Assuming a scope height of 1.6" above the rife bore.

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Bollocks

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Originally Posted by jakewire

Lets just say his hand load is a 140 gr sst
and
lets just say he's just over 2700fps
If this is the case or close and he's 6 inches high at 100yrds he'll have roughly a 350yrd zero which will put him just over 8" high at 200 yrds.

Even if he's using a standard interlock type 100fps slower he's still zeroing about 320 yrds and at 6" high at 100 puts him over 7" high at 200

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Bollocks, looks like I owe a box of beer and have to put my tail between my legs. Might just wait till he's back from a trip on sunday before telling him though

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Originally Posted by Hades

You are right.

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The correct response in any argument for the married man - irrespective of validity.

Think of it this way - to move up four inches at 100 you’re looking at 4moa, or 16 clicks. 4moa at 200 will be 8”, so you’ve come up 8” from your original zero. If your original 100 zero was 2” high, and 0 at 200, you’ve come up the equivalent of 4moa, and therefore are now 6” high at 100, and 8 at 200. Bobs your uncle - no need for fancy maths!

He is wrong you and I both know that! He will miss a good bull this weekend and blame his rifle it is shooting 139 gr interlocks at a very mild 2550fps :-)



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But a nightforce and you will never have to worry about your scope been knocked out.
Bending the barrel is a different story!

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Pictures are good. For the spread of angles at which we launch our bullets through choice of zero - typically all within 1 degree of horizontal - the shape of the trajectory for a given bullet & muzzle velocity remains substantially unchanged.
This fixed shape of trajectory, commonly described in figures of fall below a horizontal line of launch - drop data - may then be used to predict the bullet's path by rotating the trajectory until it passes the line-of-sight for any chosen zero distance.

Bigred, the info you provided in your initial post gives the blue trajectory below: zeroed at 200, 2" high at 100, with the scope line-of-sight 1.5" above the bore. Height above & below the line-of-sight is on the y-axis, distance out from the rifle on the x-axis, so the bullet leaves the muzzle 1.5" below and is sent upwards through the line-of-sight, returning back through it at the chosen zero. G1BC=0.5, MV=2695ft/sec is one combination that would get you close if distance is in yards.

Attachment 79131

Your mates bullet follows the red path. And because he shoots 4" higher than you at 100, his bullet will be EXACTLY 8" higher than yours at 200, 12" higher than yours at 300 etc. - as 7x64 indicated in an earlier post. I've assumed here that your mate is shooting the same bullet & MV as you and only his chosen zero is different (around 340yds depending on exact BC & MV combination), so the curve of the path of the bullets is the same for both.

On first inspection the shapes of the trajectories may not look the same in the first graph, but this becomes more apparent when comparing to the lines of rotation pivoting about the muzzle, added in the second drawing below.

Attachment 79132

Fuck that shit hurt my head

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Originally Posted by Cartman

Fuck that shit hurt my head

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Was just saying to my mate the other night as we dragged a boar back to the truck "got lucky with the lines of rotation pivoting about the muzzle on that shot. :thumbsup:

Hi Big Red

Your geometrical reasoning is not correct but yov've got the good sense to SMell a rat. AII
power to you for knowing yourself and getting to the bottom of it!

Usual point of impact :
Zero inch high at 200
Two inch high at 100

Actual point of impact at 100 : 6 inches high

He's out by 4 inches at 100

He will be 8 inches out at 200.

No need for argument.

If you want to be sighted in for 200 then you need to shoot at 200.

Try firing a 5 shot group at 200 and see where it goes. Then fire another at 100 and see where that is (and how big it is). If your groups turn out to be around an inch at 100 and around 2 inch at 200 then you can adjust on 3 shot groups to get sighted in and use 3 shot groups next time. Otherwise you have some uncertainty exactly where your rifle actually is shooting on average and you should rely on 5 shots at a time. Seems like a lot of factory ammo but better than shooting 3 on target and missing two at an animal.

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Originally Posted by bigred

Bollocks, looks like I owe a box of beer and have to put my tail between my legs. Might just wait till he's back from a trip on sunday before telling him though

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Buy him a box of Waikato ...youl still win the war :P

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Originally Posted by bigred

So I need help.

To cut a long story short I'm currently having an argument with my hunting buddy about how far out our rifles are. Mine's out, I took i big knock and needs sighting in I know that.

Not sure if he's having sympathy pains but says at 100m he's 6 inches high. That's fine we both agree. However where the argument starts is if he's 6 inches high at 100m, how high is he at 200m? We both normally sight in spot on at 200m and for arguments sake are 2 inches high at 100m. Then the shit hit the fan and all sort of threats have been made.

I'll admit I don't know enough about ballisitics and physics to work equations out, i buy factory ammo and use the info on the back of the box for bullet drop etc. By my reckoning if he's 6 inches high at 100m, and normal bullet drop of 2 inches over 200m, he should be 4 inches high at 200m. I'm hoping that I'm not a complete moron here but he reckons that at 2 inches high at 100m, he's 8 inches or more high at 200m. I'm struggling to see how, but like i said don't know loads about this, if someone could explain in simple terms who's right I'd really appreciate it. I'm hoping i'm on the winning side and save myself a box of beer.

If it helps, he fires a 6.5X55, hand loads but I don't know bullet weight/grain weight.

Cheers

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going by norma ballistics 6.5x55 140gr nosler partition muz/v 2690 6"high at 100yrd = zero at 337yrd high 7.99" at 200yrd

Attachment 79209