problem with Zeiss Rapid Z 800 scope

[dmax1800]

I have a Zeiss HD5 5-25x50 with Rapid Z 800 reticle on my 300 win mag. I've tried to use Zeiss's ballistic calculator for the optimum power setting. Problem is that when I zero my scope at 200 yards (as recommended), then with the recommended power the first hash mark for 300 yards results in the bullet being 3 inches low. I have to move the power level down 2 magnification levels to get the correct elevation for 300 yards. This has happened on 2 different scopes. Zeiss has been absolutely NO HELP. At this point I don't feel I can trust the reticle/calculator combination and don't want to shoot 100 or more rounds to experiment at different yardages out to 800 yards. Reason I don't want to shoot another 100 rounds: I had a good load developed. Very consistent 3/4" at 100. Guy at Nosler told me to stop. But I had to try another seating depth and got groups of .6, .4 and .2 inches. Yes, .2 inches.

Here are my details:

Nosler 180 gr Accubond, 73 gr of IMR4831 powder, Norma brass (trimmed, weighed/sorted, neck turned, flash hole reamed, primer pocket uniformed, annealed every 3 firings), WLRM primer, 26" Hart #5 barrel, muzzle velocity of 3050 fps, altitude 1000 feet, temp 50 degrees, Magnetospeed V2 chronograph.
Magnetospeed said that if the chrono was bad, it would be very inconsistent. I'm getting ES of 28 and std dev of 9, so the velocity should be close. They said readings should be within .5%.

The calculator says I should be using 22 power. Even if I lower the muzzle vel down to 3035 (.5% reduction) AND lower the BC down to .482, I still get a power of 21 with the calculator. I have to lower the power down to 20 to get the correct elevation for 300 yards and the first hash mark.

Has anyone else successfully used the Zeiss ballistic calculator with the Rapid Z reticle?

Anyone have any ideas why the calculator isn't very close to real world?

 

[bruce_ventura]

A ballistic calculator will get you close using published BC values, but not necessarily spot on. The bullet drop profile designed into the RZ-800 will not be a perfect match to any specific bullet drop profile at any specific atmospheric condition. Bottom line is you will have to confirm your drops at the max range anyway.

I dial in this type of reticle using the following method. First I zero at 100 or 200 yds. I use my ballistic calculator to determine the magnification value for the max range that I plan to shoot. I set up a target at the max range and fire a group of 3-5 rounds, using the appropriate hold off mark for that range. I find the centroid of the group relative to the aim point. I secure the rifle in a rest with the hold off mark aligned with the aim point. I dial the magnification until the hold off mark is aligned with the centroid. I then mark the magnification ring with a small dot using a silver Sharpie.

Finally, I set up a target at an intermediate range, fire another group, and check accuracy of the another hold off mark. Repeat as necessary.

I use the magnification value that you determined this way to dial in the BC or MV in the Zeiss (or other) software so that I can tweak in the magnification for other atmospheric conditions.

FYI, I don't use ballistic hold off reticles beyond 500 yds when big game hunting. Beyond that range, I would dial my hold offs.

 

[Minkey]

I have the same Scope on 300 WSM. I have tried a cartridge, (Winchester 150gr E Tip) which is SUPPOSED to be spot on. At 600yds comes in 6.5" low, at 800yds 29" low. Not very impressed really. I expected some inconsistencies but this is huge. Anyone else?

 

[jsthntn247]

That's why bdc reticles suck. They should put Moa or mil based reticles in all of them. If shooting past 300-400 you should be dialing anyway.

 

[graywolf]

that's unusual in my experience with rapidz reticles, usually they are spot on if your data is correct

You can double check it by selecting the "drop" button on the web calculator, eg at 22x the 300 yd sub tension corresponds to 6" drop for the bullet and velocity you are using. What is your actual drop at 300 yds when you are zeroed at 200? Is it more than that?