This device was throughly tested and evaluated on one of the tactical forums web site.
Bottom line and it's something I discovered in some of the long range and tactical courses I've taken. Using a cosine for long range shooting is not as accurate as most folks think. At relativly short ranges and mild angles those devices work well, but at longer ranges and steeper angles they are not very accurate.
Cosine angles will give you the corrected yardage to your target. However, your bullets time of flight is still longer to that cosined target than it would be if it was shot at on a level range.
Sorry I almost confused myself. I used my ballisitc program for these numbers.
Let say I'm shooting at a level range at 500 yards. My bullets time of flight was .653 seconds to the 500 yard target.
Now I'm out west on a hunt and I want to make a shot at a rock chuck. My laser shows it's 650 yards to the rock chuck, but it's at a steep angle. I use my cosine indicator
and it shows the actual yardage to the target is 500 yards.
I make my adjustments for a 500 yard shot, pull the trigger, but miss. The reason is my bullet is still traveling 650 yards even though the corrected angle to the rock chuck was only 500 yards. My bullets time of flight was really .850 seconds to cover that adjusted cosine 500 yards. That means my bullet was in flight and being pulled down by gravity almost 25% (23.2%) longer than it would have been if it was fired on a level range.
I hope this makes sense.
[ 10-19-2004: Message edited by: Jeff In TX ]