ballsitics software wizard needed.

C

crout

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I was playing around with some software online trying to find my velocity by playing around with some know info

elevation- 2500ft+/- 100ft
temp- 6 celcius
bullet-139gr .264 dia
B.C.- 0.615
100yards-shoots 3" high
300yards-shoots 2" low(actually 0-4")
kpa-101.97

my calculations say i'm doing an easy 3300fps? that to me is crazy. can anyone confirm or deny and no i don't have a chrony:)
 
Last edited:
cycbb486 said:
you are talking 6.5 mm?

Unless it is in a honking huge case I would say you are not going that fast.

CBY
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yeah .264.
i don't think i'm going that fast but how do i explain the bullet drop? the only way i can get the bullet drop to match is to have that velocity. what am i missing with my ballistics calculations?
 
What is your sight hight in reality and in whatever ballistics program you are using? If your sight height is actually higher than the input you give the program, you will overestimate the velocity when estimating it based on bullet drop, assuming all else is correct.

RG

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Ruffed Grouse said:
What is your sight hight in reality and in whatever ballistics program you are using? If your sight height is actually higher than the input you give the program, you will overestimate the velocity when estimating it based on bullet drop, assuming all else is correct.

RG

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explain sight height to me.
i just plug the numbers in the program until the results show 3" high at 100yards and 2" low at 300 yards. i can drop velocity in the program down to 3100fps and still get something like 3.6" high at 100 and 2.4" low at 300. either way based on the 6.5x55 cartridge and with my powder charge/barrel length i should, in theory, be about 2700fps.
 
Ruffed Grouse said:
What is your sight hight in reality and in whatever ballistics program you are using? If your sight height is actually higher than the input you give the program, you will overestimate the velocity when estimating it based on bullet drop, assuming all else is correct.

RG

<><
Click to expand...

thanks, and thanks rockenroad for the pm. i had my sight height at 0 i moved it to 2" and got the numbers i was looking for. 2770fps with 3" high at 100yards and 2.6" low at 300 yards. thanks everyone:D
 
i was wondering this myself if it was possible to gauge your velocity without using a chrono. So, you just zero your rifle at 100, shoot at 100. move out to 200 with your rifle still zeroed at 100, shoot. Move out to 300 with it still zeroed and shoot again? Measure the distance between holes and then plug into a BC? does this sound right?
 
crout: glad that worked out!


knockturnal said:
i was wondering this myself if it was possible to gauge your velocity without using a chrono. So, you just zero your rifle at 100, shoot at 100. move out to 200 with your rifle still zeroed at 100, shoot. Move out to 300 with it still zeroed and shoot again? Measure the distance between holes and then plug into a BC? does this sound right?
Click to expand...

What crout has done is one step more, I think. I don't know if there are any programs that will back-calculate velocity from other observed ballistic data. I gather he has filled in as much of the ballistic data as he could, and then used trial and error to find the velocity that produces the observed trajectory. This should get you in the general ballpark, but I don't think it will really get you any closer to the truth than you'd get out of a load manual anyhow. The answer would be really sensitive to the trajectory values that you have observed. Unless you have a very accurate rifle, it will be hard to estimate exactly what the drop is at longer ranges. Being of by, say an inch at two hundred yards, in your estimated trajectory might make a big difference in the velocity estimate.

RG

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knockturnal said:
i was wondering this myself if it was possible to gauge your velocity without using a chrono. So, you just zero your rifle at 100, shoot at 100. move out to 200 with your rifle still zeroed at 100, shoot. Move out to 300 with it still zeroed and shoot again? Measure the distance between holes and then plug into a BC? does this sound right?
Click to expand...



you can do it that way. I didn't shoot at 200, but the numbers will still be the same in the end. you'll just have more reference points to compare to with the ballistics calculator.
I shot a group(10+ rounds) at 300yards and averaged my results, i was about 2-3" low of what i was aiming at. then i moved to 100 yards and shot at the target(6shots, no reason for 6). the average was exactly 3" high from the point i was aiming at. i used the calculator in the link above.
 
Hi, Crout I ran your numbers in the Nightforce Program and it came up with these Calcs
100 yds +1.5
150 yds +1.0
200 yds 0.0 in
250 yds -1.25
300 yds -2.5
350 yds -3.75
400 yds -5.25
450 yds -6.75
500 yds -8.25
 
The bottom

line is NOTHING is a substitue for a chrony.

I use it whenever I change lots of powder. It is the quick way to see where one is at and where they possibly need to go.

CBY
 
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