Working out bullet drop distances

s8mdevo

Well-Known Member
Tell me, can you work out bullet drop for 300,400,500 metres backwards if I already know exactly how far my bullet drops at 600 metres?

For example I have a 200 metre zero and I'm dialing 100 clicks to be bang on at 600 metres, is it possible to work backwards with this information and work out the 300,400, and 500 click values?

All advice welcome
Cheers
 
The ballistic apps will do it for you, Strelok has the option to correct with real data.
 
I have seen this option. When I input my actual field data it increases the fps of the bullet by over 200fps. I am not sure if the app is at fault or my chronograph has given false reading. I have a nice new magneto speed so would prob think that it is showing a correct reading.
 
a bit of fudging with a ballistic program will get you there , get all your known data and input it very carefully then fudge the velocity to get your 600m drop to match your actual drop then the other ranges should be close
 
I have seen this option. When I input my actual field data it increases the fps of the bullet by over 200fps. I am not sure if the app is at fault or my chronograph has given false reading. I have a nice new magneto speed so would prob think that it is showing a correct reading.


the chrono maybe a bit off or you can change the BC to match your data and keep the Chrono reading Strelok can do either with its corrections
 
a bit of fudging with a ballistic program will get you there , get all your known data and input it very carefully then fudge the velocity to get your 600m drop to match your actual drop then the other ranges should be close

This is the plan, I have all the data and drops for 600 metres, but couldn't understand why Strelok was not playing ball. I am heading to Bisley next week and wanted to shoot some distances between 200 and 600 to check drops so wondered if I altered my bullet velocity to match up with real field data would the Strelok app be correct at these distances in between.
 
This is the plan, I have all the data and drops for 600 metres, but couldn't understand why Strelok was not playing ball. I am heading to Bisley next week and wanted to shoot some distances between 200 and 600 to check drops so wondered if I altered my bullet velocity to match up with real field data would the Strelok app be correct at these distances in between.

I found when I did something similar that it took several attempts to get all the data correctly entered into the App. Scope height was one issue, my real world velocities weren't exactly the same as the magnetospeed either. By truing up at the end of each range session and carefully rechecking the inputs I eventually got a profile in the app that closely matches the real performance of the rifle. It probably took me about 18 months from starting with the App to get to a point that I am comfortable with what it is telling me, but I don't get on a range very often.

Have fun.

JCS
 
I use ballistic and find it very good , especially bryan litz's g7 data

bc's can need fudging but I wouldn't go there first

it depends on what your after , first round hits on bunnys at 600m or hitting the screen on the range so you can make fine adjustments with subsequent shots
 
When I am doing this I use wall paper 4ft high yes a high back stop is used I then zero at x norm 100. then I draw a line in the centre of the sheet mark off in inch lines so 100 would be nr the top so I can also move to 50yrds etc . I have my Zeiss chart as this is what the scope is and set up by shooting three rounds then move to my 100,125,150, and so on you get it , I do this to my max range then see if the chart matches my target if not I ajust by the amount of diff' at 300 shot, then mark off the shoots and re shoot the list again, but they are not far out and if it were deer they would fall over ? Failing that book a point at the Bisly with a few mats and get it sorted that way . my club is lucky we have use of Stanta so for my long range stuff I just use a pal to mark off 1-1200 . vie the 100yrd points.
 
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I found when I did something similar that it took several attempts to get all the data correctly entered into the App. Scope height was one issue, my real world velocities weren't exactly the same as the magnetospeed either. By truing up at the end of each range session and carefully rechecking the inputs I eventually got a profile in the app that closely matches the real performance of the rifle. It probably took me about 18 months from starting with the App to get to a point that I am comfortable with what it is telling me, but I don't get on a range very often.

Have fun.

JCS

And here I was thinking I would have this all worked out in a couple of visits to the range!
 
Ultimately the aim is to be able to dial to max 600m distances for first hit kills. At the moment though I could hit something at 600m but I'm off in the middle so want to get the data bang on all the way from 200-600m
 
then you are going to have to put the range time in and get real world data that you have verified plus build up a database of how your rifle/ammo combination behaves in different weather conditions/temps etc

sadly there is no shortcut to being bang on at all distances !
 
then you are going to have to put the range time in and get real world data that you have verified plus build up a database of how your rifle/ammo combination behaves in different weather conditions/temps etc

sadly there is no shortcut to being bang on at all distances !

Figured as much. I have data for 600m, so a visit to 400m should give me a good platform to start from.
 
The further out you go distance wise, the less reliable a G1 profile will be for most target or boat tail bullets. Use a G7 profile and then work back from there. If you don't know the G7 for the bullet you're using, I may have it here in my data and happy to help if I do.

There are a few variables as already mentioned which add up to ballistics apps rarely tying in with measured data first time out. Its a theoretical model that needs calibrating as rubbish in = rubbish out otherwise.

To a few hundred yards, G1 may be sufficient but I've found that beyond about 300, it's next to useless, and the G7 is a far better approximation, so there's the first thing. Even the G7 will vary slightly with velocity hence depending on range, you'll inevitably have to do a little fudging to get a match. G1 profiles almost always over-estimate down-range velocities the further out you go. The difference at 1000 yards between G1 and G7 for, say a .308 matchking equate to 100fps at least, if not more, as I recently discovered. I would expect though if you entered a G7 in for your 600 bullet drop and work backwards, it will be pretty close and your velocities may tie up better.

Other variables come into play, and there's been discussion in the past whether variations, or individual chamber imperfections will mold a bullet slightly out of shape before it is fully swaged, hence slightly alter BC. Then there's variations in rifling and lands depth which may also slightly have an effect on BC. Add any inaccuracies in scope height measurement and slight chrono inaccuracies (none are 100% reliable) and its not hard to see why theoretical data may not marry precisely with measured data.
 
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The further out you go distance wise, the less reliable a G1 profile will be for most target or boat tail bullets. Use a G7 profile and then work back from there. If you don't know the G7 for the bullet you're using, I may have it here in my data and happy to help if I do.

There are a few variables as already mentioned which add up to ballistics apps rarely tying in with measured data first time out. Its a theoretical model that needs calibrating as rubbish in = rubbish out otherwise.

To a few hundred yards, G1 may be sufficient but I've found that beyond about 300, it's next to useless, and the G7 is a far better approximation, so there's the first thing. Even the G7 will vary slightly with velocity hence depending on range, you'll inevitably have to do a little fudging to get a match. G1 profiles almost always over-estimate down-range velocities the further out you go. The difference at 1000 yards between G1 and G7 for, say a .308 matchking equate to 100fps at least, if not more, as I recently discovered. I would expect though if you entered a G7 in for your 600 bullet drop and work backwards, it will be pretty close and your velocities may tie up better.

Other variables come into play, and there's been discussion in the past whether variations, or individual chamber imperfections will mold a bullet slightly out of shape before it is fully swaged, hence slightly alter BC. Then there's variations in rifling and lands depth which may also slightly have an effect on BC. Add any inaccuracies in scope height measurement and slight chrono inaccuracies (none are 100% reliable) and its not hard to see why theoretical data may not marry precisely with measured data.

Took your advice and changed setting to G7 in the Strelok app and as you mentioned it appears to be a lot closer to the mark (actually within 3 clicks of the range data I have shot already). It definitely appears to be a much better estimation than set on G1. Thanks for the advice ChesterP
 
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