Admittedly, not a bench rest shooter (at least a good one) but i chron'ed my 26" 6.5 creed and come up with 2762 fps ...140 Berger hybrid, 41.6 gr H4350, Fed gm205m....005 off. Lapua brass. On two different ballistic programs zeroed @200, for 500 yds, i get moa come up at 7.60 ( @75 degrees)...but to be on bull at this range, i only dial up 6.75,,,,right at 1 moa difference. Temp is right, scope height is right, all info on ball program is correct....so why the difference? one of the ballistic programs has a fps correction at corrected moa adjustement at given yardage,,,,it shows 3039 fps.....i believe the 2762 is a true fps.....so what am i doing wrong, or is that not a big moa difference? Thanks for any insight to this
ballistic charts way off from bench shots
- Thread starter rsbhunter
- Start date
Do a tall target test to make sure your click values are what they are supposed to be. I would also sight in at 100 yds to get the best zero you can. First things that come to mind. Good luck.
Paul
Paul
What Chronograph are you using? They can make a huge difference in speeds recorded. I have a cheapo Chrony that I use, but really what I do is just check for SD to see if I am getting load consistency. Then shoot the rounds at varying distances to get my "zero's" at those distances. I pay more attention to pressure signs and finding accuracy nodes than the ballistic calculators.
It is a master chrony, and all loads come out real close to what they "should" be, either to book or shooters quoted fps. Yes, scope height is within .020 by measuring with calipers (scope tube dia, action dia, distance from top of reciever to bottom of scope tube, etc) all atmospheric values are included in ballistic charts, actual conditions might be off a little, but not 5" plus worth....I dont think....rsbhunter
Your Chroney is probably set up about 10-12' from the muzzle, correct?
If so, either you or the ballistics program must calculate the Mv at the muzzle. The program I use asks for "Mv at XX yards" then it calculates
the true Mv. There may be quite a difference.
I used to use a Chroney and placed it 10 yds out and the program (JBM) allowed for that. Now, I use a MagnetoSpeed and put in zero yds. I got good come-ups both ways, and I normally shoot 600 or 1000yd,
If so, either you or the ballistics program must calculate the Mv at the muzzle. The program I use asks for "Mv at XX yards" then it calculates
the true Mv. There may be quite a difference.
I used to use a Chroney and placed it 10 yds out and the program (JBM) allowed for that. Now, I use a MagnetoSpeed and put in zero yds. I got good come-ups both ways, and I normally shoot 600 or 1000yd,
12 feet, and if I am zeroed at 200,stating zero at 100 yds, that would throw my numbers way off at other ranges...that's why they ask for the zero range. I know this is a mystery, as it should be closer than what it is...I have print outs on other rifles, a 6xc,7mag, 6.5x284 that all fall within the stated drop figures.....I have some more loads loaded up, first good day for wind, I will be at it again.....rsbhunter
Guess I'm saying try zeroing in at 100 and go by what the charts say from 200-?. I understand your 200 yd zero but it's just another solution if you haven't tried it yet.
How do you determine your scope height above the bore? that can skew the results if not measured with a degree of precision.
Sight in at 100 and get a hard zero, dial in 10 MOA, shoot second group and measure center distance between groups to rule out your scope values being off.
Shoot over another crony to verify yours, if all checks out and your input data is correct, real fire is more important than anything, tune your chart to it.
What base and rings are you using and whats your input ?
Shoot over another crony to verify yours, if all checks out and your input data is correct, real fire is more important than anything, tune your chart to it.
What base and rings are you using and whats your input ?
scope height: 1/2 diameter of action, added to distance from top of action to bottom of scope tube, added to 1/2 diameter of scope tube....i might be wrong? using calipers to measure....will do the shoot, dial up 5 moa, shoot, dial up another 5 moa and shoot again...and i do know the chrony isnt super accurate, but if it matched what the corrected drop chart shows, i'd be between about 2990 and 3009 fps....if i'm getting that fps with no pressure signs, i would be REAL surprised, with a 140gr pill......rsbhunter
Did you adjust for look angle (slope angle, line of sight angle)?
rammac, that looks alot better than what mine shows...I'm using the Berger online (berger 140 hybrids) and the G7 (Gunwerks) online......I've looked for a good windows 10 ballistic program, but I don't know that the good ones are win10 compatible....I believed that the ones I was using would work, and have for other rifles, but yours works for this one....even at 600 yds, yours shows 9.3, and my bull was 9.2, which is great.Which program is yours? Rsbhunter
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