I would not use a chronograph in the field. I would (and do) use one when I am putting together loads and sometimes during target practice to see if I start to get any unexpected changes in bullet velocity.
A chronograph is nice for getting you better data to model your bullet flight with. If you do not have one, you can use your published "muzzle velocity" for your ammo. Then, just have a really big target at further range to see where your bullet hit vs. expected.
Lets say you used Federal factory ammo with a 180 gr accubond with a estimated (from factory) muzzle velocity of 2960 fps. G7 BC for the 180 accubond would be 0.246 (0.246 G7 BC from Applied Ballistics - by Bryan Litz). You can plug those values in to (lets use the Berger model for this one) along with the height of your scope center above the center of your bore, along with atmospheric conditions ( temperature, humidity, pressure ) to give you an estimation of what your bullets flight path would be.
You have errors, always. So, when you are out practicing at 600 yds, you can use the estimates from the model to get an idea of how low you might be. Then you shoot at your target and then "dial in" to find out what your setting should be.
Hypothetical - if your load is similar to the one mentioned above, and you are 2 inches high at 200 yds, you are probably sighted in somewhere around 250 yds. On std atmospheric conditions day, you might be around 5 feet low at 600 yds. The thing is, you need to test out your estimations on targets at 600 yds. It would be good to test at 300, 400, 500 as well. The further you get out, the more important it is for you to know how far the target is and the larger 1 moa scope adjustment matters. If your scope (nice choice btw) is right on with minute adjustments then 1 moa at 100 yds is 1.0471996" inches, at 300yds it is around 3.14", at 600 yds, it is around 6.28". At 600 yds, with the previously mentioned Federal load, if the distance is 25 yds closer or further away, the height adjustment is going to be about 1 moa (based on estimation of being sighted at 200 yds with 1.75" scope height). Therefore, if you see a target at 600 and you think it is 625, on a std day, you would be around 6 inches high. Lets say then that you saw it at 630 yds, you thought it was 575 yds, you would be around a foot low. Of course, all that doesn't take into account how precise your shooting rig & you are. (ie add more error)
That is all based on the assumption that your load met the criteria entered every time with no variation (not real life - there will be some fps difference). If you are shooting instead around 2880 fps, and still shooting 2 inches high at 200 yds, well then you are probably sighted a bit closer than assumed earlier. Everything will change some. Modelling, is based off the info you put in.
That is something nice about a chrono. It lets you know while you are practicing of what your velocities are (albeit with some error), and if you are getting a wide variation in velocities.
If you don't have a smart phone, pda, or some ballistics computer with you, you can print out ballistics charts for your loads and expected conditions to give you a guideline.
I haven't even mentioned wind, angle, bullet spin, etc...
Good range estimation is very important. Laser range finders and gps and maps, using your mil-dots are methods of getting a range estimation. You need have good range estimation, unless you are sighted in at a fixed target have been consistently hitting said fixed target, and your game animal also comes to and stands immediately in front of that fixed target.
Toys are great both for giving you good data and helping you improve your estimations, nothing replaces practice. Hit some paper and gongs at different long ranges, get consistent at it.
A great book for you to read would be "Applied Ballistics For Long Range Shooting" by Bryan Litz. He has a good Ballistics program for smart phones -
Products
I use Bryan's ballistics programs.
