How is this trajectory possible?

[twoftagl]

I set out yesterday to find out my actual drops, just to compare and fine-tune the profile in EXBAL. After measuring the drops, I can't find a reasonable profile. The measured drops are so far off I must be missing something, I can't figure out how to get a 23.5" drop at 400yards and 73.5" at 600 on either shooter or Exbal.

300 wm (winchester load)
180grain bc=.438
mv2960 published (I was showing avg of 3028)
55 degrees / 300 feet / 23% / sea level pressure 30.05
200 yard zero / sight-in conditions same as above
sight height 1.925

measured drop:
400yd: 23.5" 5-shot group
600yd: 73.5" 4-shot group (one flyer excluded)


In order to get a profile to match in the given conditions, the closest I can come in EXBAL is a bc of 1.25 and mv of 2510 fps!!???!!?? That's rediculous. The 400 yard drop is about 4" lower than what it should be shooting, and the 600 yard drop is about 6" lower.

I must be missing something completely here. Only thing I can think of is when I went from 400 to 600 I neglected to set my parallax. Doesn't seem like parallax was an issue though, cause there were four within a 5.8" vertical spread which is about the moa I usually get with that load. The fifth shot was so far low that I had to rule it out. Only setting I changed on the scope was the windage, just to keep it on the cardboard.

Any ideas? The actual drops don't even add up to the dopes I usually use, 19 clicks (1/4 moa) at 400 and 42 at 600.

Chris

 

[farout]

twoftagl,

I ran the number through the Berger bullet drop calculator.

Using a 200 yard zero the drops were:
400 yards 19.0"
600 yards 67.24"

Using a 100 yard zero the drops were:
400 yards 24.02"
600 yards 74.76"

Using the 100 yard zero the number are very close to yours. Maybe you are zeroed at 100 yards?

 

[Joe King]

I set out yesterday to find out my actual drops, just to compare and fine-tune the profile in EXBAL. After measuring the drops, I can't find a reasonable profile. The measured drops are so far off I must be missing something, I can't figure out how to get a 23.5" drop at 400yards and 73.5" at 600 on either shooter or Exbal.

300 wm (winchester load)
180grain bc=.438
mv2960 published (I was showing avg of 3028)
55 degrees / 300 feet / 23% / sea level pressure 30.05
200 yard zero / sight-in conditions same as above
sight height 1.925

measured drop:
400yd: 23.5" 5-shot group
600yd: 73.5" 4-shot group (one flyer excluded)


In order to get a profile to match in the given conditions, the closest I can come in EXBAL is a bc of 1.25 and mv of 2510 fps!!???!!?? That's rediculous. The 400 yard drop is about 4" lower than what it should be shooting, and the 600 yard drop is about 6" lower.

I must be missing something completely here. Only thing I can think of is when I went from 400 to 600 I neglected to set my parallax. Doesn't seem like parallax was an issue though, cause there were four within a 5.8" vertical spread which is about the moa I usually get with that load. The fifth shot was so far low that I had to rule it out. Only setting I changed on the scope was the windage, just to keep it on the cardboard.

Any ideas? The actual drops don't even add up to the dopes I usually use, 19 clicks (1/4 moa) at 400 and 42 at 600.

Chris

Can you not use G7 BC's? What make you certain that your MV's are what they are, unless you have a very very good ie expensive chrony I wouldn't take what it says to heart. drop your MV on exbal til it matches up with what your actual trajectory is.

 

[twoftagl]

Using the 100 yard zero the number are very close to yours. Maybe you are zeroed at 100 yards?

Jeez that's scary!! Those numbers are right-on!

I've been using this zero for a while now...had to re-set the turrets when going to 200. Yesterday when I re-verified it was very close (ended up making a 1-click adjustment). I would've had to do the same thing twice. Those numbers are so darned close, though...there has to be something there...hmmmmmm

Chris