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Chaps total noob here, quite possible that I have hold of the wrong end of the stick.

Here's my question:
How do I go about calculating the relationship between the marks on any given reticle and the amount a given bullet would drop? Or to word it another way - if it set my scope bob-on at 200m and i know the bullet will be Xmm lower at 300m and Ymm lower at 400m is it possible to chose a reticle that will have the marks appropriately spaced?

Probably not explaining this very well, hopefully one of you will understand and throw a not very mathematical brother a bone.
thanks for you patience
UTB

have a look at this, it sounds as if it is what you are after.

http://www.nikonsportoptics.com/en/niko ... s-bdc.html

As @nd has posted, you can get bullet drop compensated (bdc) reticles. These scopes have markings on the reticle indicating the holdover for certain distances, but these are only calibrated for certain weight bullets travelling at certain velocities. If this isn't an issue for you, then they can be great! If not, the only other option you have is creating a "drop table" based on the ammunition you have.

If you know the weight of your bullets, the velocity it travels at in your rifle and the weather conditions you're shooting in, then a drop table will tell you how much drop your bullet will have over set distances. This will also show how many clicks you need to adjust your scope at every 100 yards/metres, depending on what units you prefer to work with.

Scopes come with minute of angle (moa) or milradian click adjustments. These two units are a measurement of angle, so in essence it's like thinking "if I want my bullet to hit the target X amount of inches higher, then I need to adjust the angle I fire at by Y amount".

If you can't find a BD reticle to suit, you can get custom elevation turrets marked for a specific from Leupold & other good scope makers.

Thanks for the replies fellas.

The only problem with all the stock solutions, bespoke reticles or marked turrets etc, is if you change your ammo's ballistic characteristics it'll all be wrong. Marking the turret is ok but is a problem if you shoot two or more different bullets.
A table stuck to the side of the stock or scope or even in the end caps can have the number of clicks, mao or mils to dial on the turrets for every different ammo choice you have and can be changed easily and cheaply.

Have a look at ACSS reticles if shooting <800 yards.

you can do this with any reticule that has marks on the vertical wire , all you do is cross reference the distance against range , so your hash marks will be for example 200m=0 ,278m= the next hash mark then 356m the next one and so on , do you get what I'm trying to explain albeit rather badly ?

Much easier to explain pictorally :)

Here's my drop table for my 6.5x47 Lapua (123gr Scenar loaded with Reload Swiss RS60). I'm a millradian guy, so follow my example with the "Come up in MIL's" column.

This data is assuming a zero at 100m with a muzzle velocity v0 = 2,900fps. There are drop values for each 100m interval. If I wanted to shoot at 900m, I would need to adjust my elevation to +8.7 MRAD/MIL for my shot to hit the target.

I have a Bushnell Elite ERS 3.5-21x50 scope with a G2 reticle (pictured below). The vertical and horizontal lines have subtensions to allow you to hold over your target. I could either dial in 8.7 MRAD into via my scope elevation turret, or I could hold the 8.7 MRAD by raising my rifle until the target lined up with ~8.5 MRAD on the vertical axis (there are only 0.5 MRAD subtensions).

With this in mind, I would always prefer to use a scope with a reticle with subtensions built in. The BDC scopes are very specific for certain calibres and loads, whereas the aforementioned types of scopes are universal - so long as you do a bit of homework and produce an accurate drop table for set distances (even better if you use data obtained in real life!).