lougonl
Active Member
The difference between the 700 yard velocity and 800 yard velocity.
400 0 MOA
500 -.50 MOA
600 +.50 MOA
700 +1.00 MOA
800 +1.00 MOA
400 0 MOA
500 -.50 MOA
600 +.50 MOA
700 +1.00 MOA
800 +1.00 MOA
Need Help
- Thread starter lougonl
- Start date
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Ok, something is not tracking right here. Try this, adjust your velocity to 2535 and post your MOA elevations for 400, 500, 600, 700 and 800. 700 should be 20 MOA, I'm hoping.
lougonl
Active Member
2535 Velocity
400 6.5 MOA
500 10.50 MOA
600 15.00 MOA
700 20.00 MOA
800 26.00 MOA
400 6.5 MOA
500 10.50 MOA
600 15.00 MOA
700 20.00 MOA
800 26.00 MOA
Suggestion: Try adjusting your ballistics solution to 2535 FPS and G1 BC to .500. BC is dependent on a velocity band and you are shooting around 2500 FPS MV near sea level or approximately an adjusted air density standard equivilent to 900 ft elevation. I'm puzzled by your 500 MOA correction, not matching up to a ballistics profile. Also, what is your ES? A 40 FPS ES will create approximately a 1 MOA difference at 800 yards. Also what is your precision at a 200 yard zero in MOA?
Try the suggestion and see what results you achieve and measure your ES and precision MOA.
Try the suggestion and see what results you achieve and measure your ES and precision MOA.
BrentM
Well-Known Member
MMERS- I was thinking, perhaps I am wrong, he was shooting groups to establish a drop confirmation. IF that is true can you rule out ES? I ruled it, just wondering.
I would say MAYBE. One sure check is to fire all of your rounds through a chronograph to verify if you are on the high end, low end or middle of your SD. How can you verify that all three shots at 400 were not on the high end of your SD and at 500 your three shots were not on the low end of your SD without a chronograph? You could also shoot more rounds at each range but sometimes this starts to become counterproductive especially with a short-lived barrel. In this case with a 308 why not if you don't have a chronograph. As time of flight increases understanding the differences in muzzle velocity variation become more and more important with predicting results. During cannon fire I would have the gun crews mount a chronograph to every howitzer. When you encountered ranging errors the chronograph was a great tool to verify muzzle velocity against that particular firing solution. Having a round hanging for at times up to a minute with ranges several thousand meters away leaves you with very little room for controllable error mistakes. The same principles of eliminating controllable errors and understanding what effects those non-controllable errors bring to the table are an important aspect to the long range shooter. If you have the tools available, use them. Many times they will give you the answer and keep your head from banging against the table.
BrentM
Well-Known Member
Good info
lougonl
Active Member
Would I be correct if I were checking to see if my scope is tracking vertical I would shoot a shot at 100 yards add 27MOA shoot at 100 yards again, would that show if the bullet was tracking off vertical?
BrentM
Well-Known Member
You could for sure. You could do a box test as well.
lougonl
Active Member
Ok great I saw that on TV once.
cohunter14
Well-Known Member
This should work really well. You should also be able to verify if the scope is tracking perfectly verticle as well (use a level to make sure that the vertical change is plumb). If your scope is not level, this would help show it.
MontanaRifleman
Well-Known Member
I don't see where you mention Barometric Pressure? That will make a difference.
Things to check...
-Correct vertical alignment of your scope to your bore, I use a plum bob
-Actual scope tracking, you can check this by locking your rifle into a rifle vice at a range and checking the travel against a yard stick @ exactly 100 yds from the scope. 120 clicks (30 MOA) should equal 31.41"
-Accurate scope height.
Off the top of my head, the cause appears to be either a tracking problem or an incorrect BC or a combination of things. Your rate of ballistic decay is greater than the BC you're using suggesting the actual BC is lower. Velocity is always suspect.
In this case your actual drops vs charted drops are less @ 400 and 500, about the same @ 600 and lower @ 700 and 800.
This suggests to me that actual velocity is higher and actual BC lower than programmed.... assuming actual scope height, alignment, and tracking are correct.
Also need to know the Barometric Pressure.
Last edited:
Lougonl,
Hope you are still hanging in there. I thought I would throw this up for you.
View attachment 308 Drop Adjustment.pdf
This ballistics profile matches the majority of your drop MOAs but doesn't quite make much sense. There appears to be an error or multiple errors in your actual drop MOA correction or you have a variety of ranging errors needing confirmation. Here is a list of steps I take to help isolate ranging errors.
1. Confirm the range. Should be pretty easy if shooting on a range with known distances or verified with a rangefinder. I don't see this as being the problem
2. Apply muzzle velocity variation to the ballistics solution. Again, it will be helpful if you can confirm your velocities with a chronograph and provide your calculated ES and SD.
3. Confirm atmospheric conditions. Has your air density changed?
4. Confirm elevation turret correction settings. Is your scope tracking correctly and have you confirmed click values and verified your zero? Have you applied the corrected solution to your elevation turret? (The later will not apply in your situation with developing actual drop comparisons).
5. Is your ballistics solution validated? Have you used two sources to validate your ballistics solution? The solution above is not validated.
Hope this helps and take one bite at a time. Good luck and good shooting.
Hope you are still hanging in there. I thought I would throw this up for you.
View attachment 308 Drop Adjustment.pdf
This ballistics profile matches the majority of your drop MOAs but doesn't quite make much sense. There appears to be an error or multiple errors in your actual drop MOA correction or you have a variety of ranging errors needing confirmation. Here is a list of steps I take to help isolate ranging errors.
1. Confirm the range. Should be pretty easy if shooting on a range with known distances or verified with a rangefinder. I don't see this as being the problem
2. Apply muzzle velocity variation to the ballistics solution. Again, it will be helpful if you can confirm your velocities with a chronograph and provide your calculated ES and SD.
3. Confirm atmospheric conditions. Has your air density changed?
4. Confirm elevation turret correction settings. Is your scope tracking correctly and have you confirmed click values and verified your zero? Have you applied the corrected solution to your elevation turret? (The later will not apply in your situation with developing actual drop comparisons).
5. Is your ballistics solution validated? Have you used two sources to validate your ballistics solution? The solution above is not validated.
Hope this helps and take one bite at a time. Good luck and good shooting.
lougonl
Active Member
Oh yea still hanging in there MMERSS.
I am starting my 7 days off tomorrow I will take these tip one at a time and start rulling things out. I want to thank everyone for the help. I will let you know how I come out.
I am starting my 7 days off tomorrow I will take these tip one at a time and start rulling things out. I want to thank everyone for the help. I will let you know how I come out.
