Is there software that...

[MrCetrizine]

... can tell me the adjustment I need to make for this:

 

My rifle is zeroed at 100m for 125gn SMK at 2000ft/s.

I want to be able to adjust the scope so that it is then zeroed for 220gn SMK at 1090ft/s.

I'd also like to be able to do that at slightly longer ranges (very slightly given subsonic). I already have software that can tell me the adjustment for the bullet I zeroed with but I want some that can transpose from one bullet to a completely different one.

 

Does it exist?

[jcampbellsmith]

I don't see how you can do that without test firing the 220 gr bullet and establishing how much windage and elevation adjustment you need? Regards JCS

[MrCetrizine]

But it should just be maths. In the same way you can calculate the drop for one bullet at different distances, you should be able to calculate the difference in drop for a heavier, slower bullet at the same distance. I just suck at maths so I can't work out out.

[jcampbellsmith]

What maths tells you where the muzzle is pointing when the bullet exits the muzzle? Up, down, left, right, or some combination of these? Also what direction is the muzzle moving in?

 

Regards

 

JCS

[Deserttech Europe]

You would need to know the physical offset from your primary rounds zero. If you know this then you can build this into the dope for your second round and easily determine your scope settings for a given range.

 

regards

 

 

Ewen

[tackb]

no software can do this , go out and zero both , note the adjustment and use the software to give you firing solutions at ranges other than your zero.

[MrCetrizine]

You would need to know the physical offset from your primary rounds zero.

That's the bit I want software to calculate.

It should just be a matter of time, gravity and mass.

 

Bullet A travels at a certain speed over a set distance and drops by x amount.

Bullet B travels over the same set distance but at a slower speed and with a greater mass and as such drops by a different x amount.

 

I should have paid more attention in physics instead of starring at Rachel Thorndike.

[jcampbellsmith]

You are forgetting that bullet A and Bullet B start from different places and are going in different directions. As soon as you pull the trigger, the muzzle starts to move in 3 directions. Up or down, in or out, left or right.

 

Regards

 

JCS

[MrCetrizine]

No, this is mostly theoretical. Assume the rifle is fixed in a position where bullet A that the scope is zeroed for is hitting dead centre of the target.

There is no wind and bullet B flies on the exact vertical axis of bullet A, just slower and heavier.

 

I think I need to email Mythbusters, they do this sort of thing all the time.

[Offroad Gary]

Harmonics old boy

[MrCetrizine]

Harmonics old boy

Don't exist in my theoretical world.

 

Also I forgot I know a guy with a masters in physics. He said it's possible and will work it out when he gets 5 minutes.

[jcampbellsmith]

No, this is mostly theoretical. Assume the rifle is fixed in a position where bullet A that the scope is zeroed for is hitting dead centre of the target.

There is no wind and bullet B flies on the exact vertical axis of bullet A, just slower and heavier.......

I don't know of any rifles that work like this......however Bryan Litz may do http://appliedballisticsllc.com/ Why don't you drop Bryan a note? He will reply.

 

Best regards

 

JCS

[Shuggy]

I think that this should be relatively simple. Plug in the data for both, but set the zero ranges to '1'. That should give you the relative drop of each at 100m. One minus the other should give you the adjustment that you need to re-zero.

 

But maybe that's total Horlicks and someone will put me straight!

 

http://www.jbmballistics.com/cgi-bin/jbmtraj_simp-5.1.cgi

[MrCetrizine]

My friend with the physics degree calculated it at 16.08 inch drop which does seem about right. No clue how he did it and he says he doesn't have the time or the will to teach me.

 

He pointed me here though ...

http://hyperphysics.phy-astr.gsu.edu/hbase/traj.html

Given some Google time, I think I can work it out.

[Offroad Gary]

Don't exist in my theoretical world.

Also I forgot I know a guy with a masters in physics. He said it's possible and will work it out when he gets 5 minutes.

What size groups can you theoretically shoot?

[MrCetrizine]

In theory, calibre-calibre. That's the beauty of it.

[MrCetrizine]

Just as a bit of context for this. A friend of mine writes computer games for a living. She's been working on a first person shooter game that hopes to add some realism to a genre that mostly have guns that shoot like lasers. I've been alpha testing the game and pointed out that their AAC Honey Badger doesn't have enough bullet drop. She needed real numbers to make the changes.

 

It has to be a balance between perfect simulation and fun to play so rough numbers that felt right are good enough.

[tackb]

Just as a bit of context for this. A friend of mine writes computer games for a living. She's been working on a first person shooter game that hopes to add some realism to a genre that mostly have guns that shoot like lasers. I've been alpha testing the game and pointed out that their AAC Honey Badger doesn't have enough bullet drop. She needed real numbers to make the changes.

It has to be a balance between perfect simulation and fun to play so rough numbers that felt right are good enough.

Why didn't you say that then in the first place , it changes everything?

[MrCetrizine]

I tried that on another forum and got two responses:

A. Why does it matter, it's a game.

B. Can I play it?

[gbal]

Would not calibre help,and BC-then I think you could get real world data -and probably quickload-that would be 'near enough' for stated application. eg here is Lapua 308w 200 g and Cor bon 190 subsonic commercial load figures : drop/drift inches 10mph wind _though you wont need wind ?

 

200g @ 1050fps BC .470 muzzle -1.5/0.0 100y 16.6/1.2 200y 0.0/4.8 300y 54.2/10.5

 

190 @1000fps .470 -1.5/0 18.1/1.1 0.0/4.4 58.8/9.7

 

 

 

 

Clearly with such a rainbow round,zeroing distance -say 100y rather than 200y as above-will have a large impact on trajectory.

gbal

[henryo]

Assuming again 100m zero I make it 31.2cm

[Chris-NZ]

The reason no software can ever do this in an individual (real) case is that varying loads often don't shoot to the same windage. It's a relatively simply matter calculating drops if you have accurate input data like MV and BC but no current system is smart enough to accurately predict windage relativities between loads.