First off, I'm not sure if this is the best place to post this, but here you go.
I have, what I think is, a decent understanding of ballistics. I want to set my rifle up with a good BZO to be able to hit targets from 0-300 yrds. In the Marine Corps we sighted in irons at 36 yrds and that was supposed to be good out to 300 yrds.
I have a red dot mounted above the carry handle. I know that sight height makes a difference in sighting in the rifle. So I need to find the best range to sight this optic in that gives me the best BZO. I used a ballistics calculator found HERE
. I just used some generic info. 3200 for velocity, 55 gr, I got the BC using the calculator on the side which gave me .309. My sight, measured from the bore to the middle of the optic, is 3.75 inches.
After playing around with the sight in distance I found that if I sight in at 60 yrds the max rise will be around 175 yrds at +3.11 inches above POA. At 320 yrds I'll be -2.62 inches below POA. So From this info it seems it would be best to sight in at 60 yrds.
Does this sound right? Is there a better way to figure this out? Am I using good info (I don't know if that BC is right for example)? Obviously I need to check what ever I do on the range but I want to have a good starting point to tweak things from so I'm not just wasting ammo.
Sounds good to me. I site ARs in at 50 meters and make easy hits out to 300+. 50 meters is about 55 yards, pretty close to your 60.
Go for it and see if it works for you! Good luck.
Hornady lists a BC of .243 for their 55gr FMJBT here
I'd also dial back your velocity unless you're shooting M193 out of a 20" barrel.
Always do only the rough zeroing on the first crossing of the sightline and the path of the bullet, and the actual zeroing on the range where the bullet meets the sight line on it's way down. Zeroing on 25 or even 50 meters isn't good enough when you have to hit targets at longer distances. Even small mistakes in the zeroing process multiply.