That gun of yours is badass, brother. What alot of people don't realize... That cut-off Oxy tank is at 609 yards. It's not tall, and it's skinny. It's not easy to hit in daylight - shiit, even when you know where it's at, it's hard to find in direct sunlight. Now, the kicker... 55gr projectiles were never meant to go that far, even at an area target, much less a point target. 460 meters is the max effective range (point target, which is man-sized) for the M16A1 firing M193 ammo.
If you have DOPE on some very good 75 or 77 gr ammo, and you switch over to 55gr range-trash ammo, obviously, your holds are gonna be different. For the 450 target, I have to hold 500 to get the 55s there. On that 609, you had to hold for 700 to get those 55s there. That's a badass task to pull off. You were crushing that thing...