Shooting a new gun - 270 WSM, 24" barrel, 1x10 twist. Bullet is a handloaded Berger 150 VLD, BC - .272-G7. Muzzel velocity 2933fps. Hawke 6-24X56 scope. 1/4MOA Turrets. Using my Android phone with "Shooter" as a ballistic computer. I shot at a four foot target to verify the scope elevation tracks as specified. I tested it over a 40MOA range. It tracked 32.5" at 100 yards instead of 31.5 turning 30 MOA up. Entered a correction factor in the computer. I'm hitting about two inches high at 500 yards, 4 inches high at 600 and 8 inches at 700. I have no idea why. Could my chrono be giving slow readings or could the BC be wrong? I can adjust the BC up to .320 and the graph looks correct for where I'm hitting.
Range Report Bullet shooting over target at long ranges
- Thread starter robertjhaley
- Start date
Re: Bullet shooting over target at long ranges
Sounds like you may want to redo your calibration. For your dopes to be that far off. How did you calibrate? Try to do it from a rest that won't move and use a marked yard stick to take the shooter out of it.
Sounds like you may want to redo your calibration. For your dopes to be that far off. How did you calibrate? Try to do it from a rest that won't move and use a marked yard stick to take the shooter out of it.
Re: Bullet shooting over target at long ranges
First of all, I shot 5 rounds, after firing two to foul the barrel, through a chronograph and averaged the numbers to determine my muzzel velocity. The velocities varied +- 20fps. Next, I zeroed the scope for 200 yards. Then I setup a 4 foot target at 100 yards with a bull at the bottom. I shot a tight three shot group, then adjusted up 10MOA and shot another group. I did this three times so the final group should have been 10.47" X 3, or roughly 31.5" above the first group. It was 32.5" so I calculated an adjustment factor for scope clicks. Beyond this, I entered all my data, including the bullet BC and selecting G7 standard, into my ballistic computer and went to the range. I entered weather, adjusted the scope and shot a group at 300 that was center of paper. I did the same at 400 and was one inch high. At 500 I was rougly 2 inches high. By 700 I'm missing just over the top of the paper. This occurs with or without the scope click correction factor. The only adjustment that seems to show the actual bullet path up to 700 yards is increasing the BC from .272 to .310.
First of all, I shot 5 rounds, after firing two to foul the barrel, through a chronograph and averaged the numbers to determine my muzzel velocity. The velocities varied +- 20fps. Next, I zeroed the scope for 200 yards. Then I setup a 4 foot target at 100 yards with a bull at the bottom. I shot a tight three shot group, then adjusted up 10MOA and shot another group. I did this three times so the final group should have been 10.47" X 3, or roughly 31.5" above the first group. It was 32.5" so I calculated an adjustment factor for scope clicks. Beyond this, I entered all my data, including the bullet BC and selecting G7 standard, into my ballistic computer and went to the range. I entered weather, adjusted the scope and shot a group at 300 that was center of paper. I did the same at 400 and was one inch high. At 500 I was rougly 2 inches high. By 700 I'm missing just over the top of the paper. This occurs with or without the scope click correction factor. The only adjustment that seems to show the actual bullet path up to 700 yards is increasing the BC from .272 to .310.
Re: Bullet shooting over target at long ranges
Depending on your brand/model chronograph, that's very likely the problem. I use on occasion just a very basic generic chrono (shooting chrony) and it always seems to read higher than actual, by about 30-50fps average. Sent it to the manufacturer and they sent it back claiming "it's within spec tolerance". No big deal as I like to verify with actual field data at distance anyway.
Your BC is probably correct, but you might very well be shooting slightly faster than the data you entered.
I typically use the factory supplied BC value, but adjust the velocity to match my actual data out to 1500-2000yds. I try to zero, shoot 2 shots each at 700 yds, 1000, 1500 and 2000 over a somewhat short period of time (so the weather conditions don't have time to change much). Based on those actual drops, and current environmental/weather conditions, I adjust the velocity in the calculator to match the actual path. From then on I've got very accurate data at all ranges.
Seems to work well for me.
Depending on your brand/model chronograph, that's very likely the problem. I use on occasion just a very basic generic chrono (shooting chrony) and it always seems to read higher than actual, by about 30-50fps average. Sent it to the manufacturer and they sent it back claiming "it's within spec tolerance". No big deal as I like to verify with actual field data at distance anyway.
Your BC is probably correct, but you might very well be shooting slightly faster than the data you entered.
I typically use the factory supplied BC value, but adjust the velocity to match my actual data out to 1500-2000yds. I try to zero, shoot 2 shots each at 700 yds, 1000, 1500 and 2000 over a somewhat short period of time (so the weather conditions don't have time to change much). Based on those actual drops, and current environmental/weather conditions, I adjust the velocity in the calculator to match the actual path. From then on I've got very accurate data at all ranges.
Seems to work well for me.
Re: Bullet shooting over target at long ranges
I will give that a try. thanks!
I will give that a try. thanks!
Re: Bullet shooting over target at long ranges
I agree,
Use the initial data just to get you close enough. Then, tweek your input data to get the proper real world results. It gets you the desire information you need to hit the target.
I was using Strelok and was having a similar problem. I had to either tweek the BC or velocity to match where I was actually hitting. Once I did that, my drop card was dead on. So, then I could print, laminate and keep it on my rifle. Even the online JBM program was just a tiny bit off.
I'm not happy that the data wasn't perfect and had to be tweeked, but it did eventually provide the neccessary data I required.
Just my .02 cents.
I agree,
Use the initial data just to get you close enough. Then, tweek your input data to get the proper real world results. It gets you the desire information you need to hit the target.
I was using Strelok and was having a similar problem. I had to either tweek the BC or velocity to match where I was actually hitting. Once I did that, my drop card was dead on. So, then I could print, laminate and keep it on my rifle. Even the online JBM program was just a tiny bit off.
I'm not happy that the data wasn't perfect and had to be tweeked, but it did eventually provide the neccessary data I required.
Just my .02 cents.
Re: Bullet shooting over target at long ranges
I pulled up your bullet specs in my ballistic software bullet library, it indicates the bc for that Berger VLD .277 150 gr SD: 0.279 Drag Function: G1 BC: 0.535.
I shoot a 6.5 CM w Berger 140gr VLD Drag Function G1 BC: 0.629. I don't know what the G7 figure would be. I hope that helps.
I pulled up your bullet specs in my ballistic software bullet library, it indicates the bc for that Berger VLD .277 150 gr SD: 0.279 Drag Function: G1 BC: 0.535.
I shoot a 6.5 CM w Berger 140gr VLD Drag Function G1 BC: 0.629. I don't know what the G7 figure would be. I hope that helps.
Re: Bullet shooting over target at long ranges
If your chronograph is 10'-15' in front of the muzzle you're not actually recording the velocity at the muzzle. As many people who have purchased the Magneto speed chronograph have discovered, you are losing 10-15fps by the time the bullet gets to the chrony.
Add 12fps to your MV and see if the calculator matches real world data. If not, and it's reliable, adjust your BC to match your real world data.
If your chronograph is 10'-15' in front of the muzzle you're not actually recording the velocity at the muzzle. As many people who have purchased the Magneto speed chronograph have discovered, you are losing 10-15fps by the time the bullet gets to the chrony.
Add 12fps to your MV and see if the calculator matches real world data. If not, and it's reliable, adjust your BC to match your real world data.
Re: Bullet shooting over target at long ranges
I went back to the range over the weekend. I started at 100 yards and moved my way up to 900 in 100 yard increments. I started adjusting the muzzle velocity at 500 and punched a 4 shot group in 5 inches at 800. At 900 the wind pulled the bullet left and broke the target frame so I called it a day. Plus it was 98 degrees in Northeast Texas with enough humidity to power a steam engine.
The technique worked. The muzzle velocity I ended up with is 2950. My chrono showed 2905. I also purchased the Applied Balistic program for Android. It's almost identical to Shooter but has a few new features.
I went back to the range over the weekend. I started at 100 yards and moved my way up to 900 in 100 yard increments. I started adjusting the muzzle velocity at 500 and punched a 4 shot group in 5 inches at 800. At 900 the wind pulled the bullet left and broke the target frame so I called it a day. Plus it was 98 degrees in Northeast Texas with enough humidity to power a steam engine.
The technique worked. The muzzle velocity I ended up with is 2950. My chrono showed 2905. I also purchased the Applied Balistic program for Android. It's almost identical to Shooter but has a few new features.
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