Try DOPE Cards

Metal range cards. Sold individually.

3 Variants: 5.56, .308 and 6.5 Creedmoor.

Back in stock after several years of absence....

While there are a few other really good cards on the market, this addresses a need that others do not.....to have data when you don't have any. This data has been pulled from years of confirmation and an average of where stuff hits across a broad spectrum of barrel lengths and environmental conditions. It may not be perfect but it will get you very close. Range it, put the DOPE in, and shoot it. They are made of metal and impervious to rain and snow. Throw it in your data book or lanyard it to your gear so you always have it. 

While it does not negate your need to have confirmed DOPE for your rifle, this will get you a head start and won't fail when your batteries and what not do.....