My best friend, has a Nikon Prostaff 3x9 x 40 with the bullet drop compensator. I have heard that they are calibrated to a 150 grain .308 load. Does anybody know. We are trying to plan out his best use of the compensator. He has never had a chance to shoot it over 100 yards yet. The nearest range we can go to is several hours away & I am not sure we can shoot at paper at longer ranges there. I tried to talk him out of the BDC when he bought the scope, but he is bound & determined to use it. He is shooting hot 7mm Remington magnum handloads that I am sure are a foot or more off to the 500 yard reticle at 500 yards. I think his best bet is memorize his 7mm trajectory & memorize the ballistics for the compensator, and adjust accordingly. Any advice out here??
In the booklet that comes with the scope it should say where to zero depending on what you are shooting. I've read that for magnum cartridges Nikon says to zero at 200. Regardless of whether he zero's at 100 or 200, he still needs to shoot targets farther out to verify which hold over mark to use , and any and all turret corrections to make. I would write everything down when you do that and make a drop card and tape it to the stock.
Facts are, bullet drop compensators only work for one make/type/weight bullet leaving at a specific muzzle velocity in one specific atmospheric condition (altitude, humidity and temperature). Otherwise, they will be off several MOA (sometimes many) at very long ranges.
If you don't know what specific trajectory parameters a scope's set up for and know your bullet matches it (muzzle velocity the same is most important), you're guaranteed to have incorrect hold over data with errors increasing as range increases.
You'll have no errors if you get zeros at different ranges in the areas you'll shoot in, then record those zeros in you mind or on paper to take with you.
Best way to convince someone that BDC's are not all that great is to use ballistic software (Sierra Bullets Infinity?) set up for different bullets, temperature and altitudes for two muzzle velocities 100 fps apart for every hundred yards out to 1000. When folks see the differences down range, they usually have second thoughts about BDC's.
I like the drop compesator reticles, "but" and this is a 800# gorilla but. It has to be worked out with every rifle and every cartridge. It requires an ample range, plenty of ammo, and plenty of patience which may well be the hardest.
My first real understanding of how to utilize a bdc reticle came when I read and finally understood the instructions that came with a Ziess, thier web-site has a program that when you fill in the appropriate criteria (cal., weight, temp., altitude, ect.) it tells you the appropriate power to set the scope on to match up with that particular cartridge. For example out of my .270 Win using a 130 grain sp at normal velocity the program recommended setting the power at 8.6 to match bullet drop with a 200 yard zero. When I tested it in the field it worked like a charm.
So I extrapolated with other bdc reticles using known distances, a big target to find actual drop then marked the target with a heavy dry marker and adjusted the power of the scope to match the bullets drop. Example: my .308 using a Hornady 168 A-Max matches a Leupold long range reticle set at 9.75 when zeroed at 200 yards.
Here is the crazy part, I've been hunting since I was a young boy and my varmint rifles have scopes with lots of power and fine crosshairs no bdc, knowing the average size of a critter and using some Kentucy windage in conjunction with knowing the bullets drop I've managed really well with momentary calculations in my mind, steady, squeeze. Nothing replaces knowledge coupled with practice.
