I bought 1 to be used on my 300 rum ,didnt know it when i got it ,got a good deal on it at an auction but it says on the paperwork its for 308. With my 300 rum i start on the 4th line and by the 10th im out to 1400 yds. I really like the thing and i had to shoot each line to verify what yardage it was but hey that was fun building a chart.lightbulbOnce i got it done i look at my chart and fire away no matter what the yardage isgun)My 300 is shootin a 190 VLD at 3100 fps, if you got something around 2800 ,2700 fps it would be a lot closer to match the reticle drop.I can go pull out the paperwork and give you particulars if you want.