Re: anyone ever tried these?
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">how do they compensate for chang in temp, elev. etcc....</div></div>
Well, they can't, of course. You have to do that yourself.
A BDC turret is great as long as you're not shooting past 600 yards.
Beyond that range, you'll have to take the atmospheric conditions into account, as well as how much your muzzle velocity changes with temperature.
Which is why I consider them a waste of money. Just memorize your dope for 600 yards and less - it's just 5 numbers, after all - and then figure out a system for calculating your settings beyond that distance.
I'm fond of a tiny dope card taped inside my rear lens cover, but there are many ways to skin that cat.
OTOH, the economy is in a recession, and if people want to spend their money on shooting equipment, I'm all in favor of that. I'll spend mine on ammo and training.